Student @ Fresno State , Madhu , Madhusudan Katti

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  • March 18, 2009
  • 09:08 PM
  • 1,864 views

Urban forestry through the lens of "socio-ecological systems"

by Madhu in Reconciliation Ecology

Contributed by Seth Reid, following a vigorous class discussion with guest presentation by Genevra Ornelas.

Our March 4th class discussion revolved around urban forestry and how it pertained to an article written by John M. Anderis, Marcos A. Jannsen, and Elinor Ostrom. This article provided, “A Framework to Analyze the Robustness of Social-ecologcial Sytems from an Institutional Perspective.”... Read more »

  • March 18, 2009
  • 08:38 PM
  • 1,810 views

Ecosystem services, biodiversity conservation, and how to pay for them

by Madhu in Reconciliation Ecology

Brad Schleder shares this summary of class discussion of two very interesting papers that Brett Moore brought to the table.

Modeling multiple ecosystem services, biodiversity conservation, commodity production, and tradeoffs at landscape scales

Erik Nelson, Guillermo Mendoza, James Regetz, Stephen Polasky, Heather Tallis, D. Richard Cameron, Kai MA Chan, Gretchen C. Daily, Joshua Goldstein,... Read more »

Nelson, E., Mendoza, G., Regetz, J., Polasky, S., Tallis, H., Cameron, D., Chan, K., Daily, G., Goldstein, J., Kareiva, P.... (2009) Modeling multiple ecosystem services, biodiversity conservation, commodity production, and tradeoffs at landscape scales. Frontiers in Ecology and the Environment, 7(1), 4-11. DOI: 10.1890/080023  

Bohlen, P., Lynch, S., Shabman, L., Clark, M., Shukla, S., & Swain, H. (2009) Paying for environmental services from agricultural lands: an example from the northern Everglades. Frontiers in Ecology and the Environment, 7(1), 46-55. DOI: 10.1890/080107  

  • December 22, 2008
  • 06:31 AM
  • 1,799 views

Phylogenomics suggest ratites lost flight multiple times

by Student @ Fresno State in Darwin's Bulldogs

Rebekah Wukits discusses recent findings about ratite evolution for Bio 135.Ratite evolution has been debated for centuries. Some of the earliest evolutionary biologists questioned whether or not ratites had a linear evolution or if the major groups had had independent origins. Richard Owen proposed that living ratites had much more in common with other flight capable groups while being united by the “arrested development of wings unfitting them for flight”. In 1951, two ornithologists, Mayr and Amadon, stated that, “the present consensus is that the main groups of these birds are of independent origins”.Traditionally, ratites have been considered to be monophyletic, or ascending from a common ancestor. They are placed in the major group Noegnathae, with the flight-capable tinamous as a sister group. Since the extinct tinamous were capable of flight, it has been thought that the ratites lost flight once in their history, then diversified. Unfortunately, simple geography contradicted this theory. All living ratites (rheas, cassowaries, emus, ostriches and kiwis) are isolated on different southern continents.  Rheas are found in South America. Ostriches reside in Africa. Emus and cassowaries are found only in Australia and kiwis can be found in New Zealand. Extinct species of ratites follow the same pattern. Moas were also found in New Zealand, and elephant birds lived in Madagascar. The question became that if flight was lost once early in ratite evolution, how did they become so spread out and isolated? The perfect answer seemed to reside in the theory of continental drift. Ratites came from a single ancestor, lost flight and were then isolated when Gondwana broke up.Though most of the recent studies of morphological and molecular ratite characteristics have supported the monophyletic theory, many still debate it. Rarely challenged is the fact that adaptations to a cursorial lifestyle, one that is adapted to running, can lead to convergent evolution, and can be misleading when basing phylogeny on morphology. This led scientists to do further phylogenomic studies in order to test the prevailing theories. These studies include data taken from genetic loci that represent the entire avian genome. In this particular study, data was taken from 20 loci that are dispersed widely throughout the avian genome. The data set included all living ratites and eight outgroup taxa. Previously done similar genetic tests have supported ratite monophyly, however these tests were more sophisticated and advanced and supported a different conclusion.The results are as follows: analysis of the data strongly supports placing the flight capable tinamous within ratites and ostriches as the sister group. If this new phylogeny is correct, the single loss of flight in ratites is unlikely. In order for all ratites to have lost flight in a common ancestor, the tinamous would have had to regain flight at a later time. It is much more likely that flight was lost multiple times do to convergent evolution than to have gained flight in the earliest ancestors, lost flight in the common ancestor of ratites, than gain flight again in tinamous.It seems more likely that ratites descended from a single ancestor, than diversified when gondwana broke up. Flight was lost in each family and convergent evolution occurred due to similar environmental conditions. Flight is very costly both energetically and morphologically. Ratites had little pressure to fly and since these features are costly to maintain, they became reduced over time.  The theories of this paper seem concrete however more study is needed. Their own genetic studies produced conflicting results. Placing tinamous within ratites has great implications for their evolution and dispersal. This idea needs to be further developed and supported.Reference:J. Harshman, E. L. Braun, M. J. Braun, C. J. Huddleston, R. C. K. Bowie, J. L. Chojnowski, S. J. Hackett, K.-L. Han, R. T. Kimball, B. D. Marks, K. J. Miglia, W. S. Moore, S. Reddy, F. H. Sheldon, D. W. Steadman, S. J. Steppan, C. C. Witt, T. Yuri (2008). Phylogenomic evidence for multiple losses of flight in ratite birds Proceedings of the National Academy of Sciences, 105 (36), 13462-13467 DOI: 10.1073/pnas.0803242105... Read more »

J. Harshman, E. L. Braun, M. J. Braun, C. J. Huddleston, R. C. K. Bowie, J. L. Chojnowski, S. J. Hackett, K.-L. Han, R. T. Kimball, B. D. Marks.... (2008) Phylogenomic evidence for multiple losses of flight in ratite birds. Proceedings of the National Academy of Sciences, 105(36), 13462-13467. DOI: 10.1073/pnas.0803242105  

  • August 27, 2008
  • 03:49 AM
  • 1,759 views

Holy magnetic cow!!

by Madhu in Reconciliation Ecology

File this one under the "who woulda thunk it?", or "why didn't I think of this?" or simply "whaaa...?!" categories! Quick, can you tell which way is north in this picture?

Do you think of asking the cow for directions? Why not? For it seems that cow probably knows which way north is! Read on...

You know, these big dumb-seeming large mammals you pass by every day, these big walking, grazing... Read more »

S Begall, J Cerveny, J Neef, O Vojtcch, & H Burda. (2008) Magnetic alignment in grazing and resting cattle and deer. Proceedings of the National Academy of Sciences. DOI: 10.1073/pnas.0803650105  

  • September 3, 2008
  • 06:13 PM
  • 1,654 views

Holy magnetic cow!!

by Student @ Fresno State in Darwin's Bulldogs

File this one under the "who woulda thunk it?", or "why didn't I think of this?" or simply "whaaa...?!" categories! Quick, can you tell which way is north in this picture?Do you think of asking the cow for directions? Why not? For it seems that cow probably knows which way north is!You know, these big dumb-seeming large mammals you pass by every day, these big walking, grazing cheese-producing happy cows dotting the picturesque landscapes of California's grassy hillsdes, or their scrawnier but holier cousins clogging up traffic throughout India? Well, there is more to them than meets the eye - in fact this curious tidbit about their natural history seems to have escaped notice from even the keenest cowboy, cattle-herder, animal husband (I'm not sure if that's what one calls someone practicing animal husbandry - is it?), or drunken late night cow-tipper, throughout history.It took some creative but fairly straightforward analysis by German scientists of satellite imagery now available via Google Earth to discover that cows, while grazing or resting, chewing cud tend to orient their bodies along the magnetic north-south axis!! And its not just cows, deer also appear to do the same! How cool, and odd, and curious is that?! And what a clever application of Google Earth imagery? This team simply measured the orientation of 8510 cows in satellite images of 308 pastures across the globe, and found that over two-thirds of the animals orient themselves along a north-south axis!! Apart from simply asking the question (who woulda thunk?), the analysis was careful enough to account for local variation in magnetic fields, and shows that the animals orient according to the local field, not geographic north!Which raises all kinds of interesting questions worth following up on, some of which you can read about in the original PNAS paper published in an early online edition this week, and in this Los Angeles Times article covering it. Here's the abstract from PNAS: Magnetic alignment in grazing and resting cattle and deer Sabine Begall, Jaroslav Červený, Julia Neef, Oldřich Vojtčch, and Hynek Burda Abstract We demonstrate by means of simple, noninvasive methods (analysis of satellite images, field observations, and measuring “deer beds” in snow) that domestic cattle (n = 8,510 in 308 pastures) across the globe, and grazing and resting red and roe deer (n = 2,974 at 241 localities), align their body axes in roughly a north–south direction. Direct observations of roe deer revealed that animals orient their heads northward when grazing or resting. Amazingly, this ubiquitous phenomenon does not seem to have been noticed by herdsmen, ranchers, or hunters. Because wind and light conditions could be excluded as a common denominator determining the body axis orientation, magnetic alignment is the most parsimonious explanation. To test the hypothesis that cattle orient their body axes along the field lines of the Earth's magnetic field, we analyzed the body orientation of cattle from localities with high magnetic declination. Here, magnetic north was a better predictor than geographic north. This study reveals the magnetic alignment in large mammals based on statistically sufficient sample sizes. Our findings open horizons for the study of magnetoreception in general and are of potential significance for applied ethology (husbandry, animal welfare). They challenge neuroscientists and biophysics to explain the proximate mechanisms.So what's the underlying mechanism cows use to sense the magnetic field? Do they also have magnetic particles in their brains like many better studied migratory species known to orient magnetically? Why do they do this? Domestic cows are not, of course, migratory any more (at least not on their own), so what might they gain by orienting magnetically? Or is this simply a vestige of their evolutionary history, from ancestors who actually put that magnet to use? And do they prefer to point their heads north or their behinds? The satellite photos are not sharp enough to tell apparently, so answering that may require some ground-truthing! Opens up a whole new line of research, doesn't it?And as for why so many humans who have spent much time with cows failed to notice this uncanny magnetism, here's a priceless quote from the LA Times, from a dairy farmer right here in the Central Valley, no less:Asked whether he had ever observed such behavior in cows, dairy farmer Rob Fletcher of Tulare, Calif., said, "Absolutely not." But, he added, "I don't spend a lot of time worrying about stuff like that."I suspect, however, that the last laugh belongs to the cows, as only Gary Larson could have guessed! Remember this from his insightful pen?That's why it took satellites to notice this particular behavior! What else have the cows been up to then?Reference:Begall, S., Cerveny, J., Neef, J., Vojtcch, O., Burda, H. (2008). Magnetic alignment in grazing and resting cattle and deer. Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.0803650105... Read more »

S Begall, J Cerveny, J Neef, O Vojtcch, & H Burda. (2008) Magnetic alignment in grazing and resting cattle and deer. Proceedings of the National Academy of Sciences. DOI: 10.1073/pnas.0803650105  

  • March 16, 2009
  • 06:11 AM
  • 1,602 views

Coupled Human And Natural Systems - a class discussion

by Madhu in Reconciliation Ecology

Heather Hanlin wrote the following summary of our class discussion on Feb 17th:

We discussed two different papers: “Coupled Human and Natural Systems,” by Jianguo Liu et al (2007), and “The Effects of Human Socioeconomic Status and Cultural Characteristics on Urban Patterns of Biodiversity” by Ann Kinzig et al (2005). The “Coupled Human and Natural Systems,” are referred to as CHANS. CHANS are... Read more »

Liu, J., Dietz, T., Carpenter, S., Folke, C., Alberti, M., Redman, C., Schneider, S., Ostrom, E., Pell, A., Lubchenco, J.... (2007) Coupled Human and Natural Systems. AMBIO: A Journal of the Human Environment, 36(8), 639-649. DOI: 10.1579/0044-7447(2007)36[639:CHANS]2.0.CO;2  

  • October 29, 2008
  • 06:17 AM
  • 1,567 views

A Bite of Beta-Carotene for Better Twitterpation

by Student @ Fresno State in Darwin's Bulldogs

Submitted by Pedro Garcia for EvolutionBirds, birds, and more birds, with over 10,000 species of birds well known and classified, one can get an array of different colors which would make even the most non-bird lover’s staring in awe. With some species having such intricate combinations of reds, yellows, greens, and blues, (such as the scarlet macaw of South America) one might ask, “Why do they have such vibrant and magnificent plumage?” (or something along those lines). It’s a well known fact that skin and feather color (yellows and reds) is linked with carotenoids in the body. One well known example is the Caribbean flamingo, known for its brightly reddish/pink color. This species of bird gets its color from the high intake of beta-carotenes obtained from its diet of crustaceans and algae. But why? What good is it to be so brightly colored? One might even think that such bright colors would be a sort of bull’s eye for predators as if saying “Hey, you…the one with the sharp teeth…I’m over here!” Well, in short, it can all be explained by loosely quoting the hip hop song… “it’s all about sex, baby!”That’s right, ongoing research has been linking brightly colored plumage in birds to…well, sex! This is the not-so-PG stuff that Darwin didn’t really talk about in his book (at least not directly), however it is merely the process of evolution at work. Researchers Negro, et al, (2002), have gone even more in depth concerning the correlation of plasma carotenoid-dependent skin color in relation to sexual selection. Their work consisted of analysis of brightness of color, not in the feathers, but, in the cere, lores, and tarsi of the small falcon the American Kestrel (Falco sparverius) along the time scale of mating season to hatching of offspring. As stated in the article, research has shown that color of plumage in birds does have an effect on sexual selection in brightly colored birds (Negro, 2002). As stated earlier, the brightness of plumage (specifically reds and yellows) is dependent on the amount of carotenoids found in the body; and beta-carotene is taken in directly from food source. Simply put, female birds choose the male with the brightest plumage because he is the one that can successfully obtain the most food, thus passing on the “better” genes to the offspring. As said before, it’s the process of natural selection at work.Although there has been much research on sexual selection and plumage color, this article delves in even further and tries to find a correlation with skin color in birds as a function of sexual selection. It seems that, as hypothesized before, there is a brighter skin hue during the mating season. However, what came next seemed to be of even greater interest. It seems that, at least among American Kestrels, the “brightness” of the skin color began to fade as soon as the mating season ended. This was directly linked with a reduction in plasma-carotenoid levels (Negro, 2002). It is believed that the reduction occurs as a trade-off between sexual selection (during mating season) and maintaining better health (post-mating season). Since the bright coloration is no longer needed after mating, it would seem that a reduction in plasma-carotenoids would allow for the carotenoids to assist in other health-related body functions (such as anti-oxidants aiding in the reduction of oxidative damage by free radicals).One concern I have with research is the methodology used for the experiments. All subjects were captive Kestrels from the “Avian Science and Conservation Center of McGill University, Canada…” which were fed a consistent diet of “…day-old cockerels” which were carotenoid-rich (Negro, 2002). This brings up my concern that the Kestrels were not mimicking natural processes, thus adding, in my eyes, a great amount of tolerance and bias to the results. It should be noted that the author does state that they have “previously shown that variation in plasma carotenoids during the mating period (April) was not attributable to diet, parasites or androgen levels” (Negro, 2002). Ideal settings that would eliminate this tolerance would include plasma collection of marked Kestrels in the wild throughout a series of mating and fledging seasons.ReferencesJ. J. Negro, G. R. Bortolotti, J. L. Tella, K. J. Fernie, D. M. Bird (1998). Regulation of integumentary colour and plasma carotenoids in American Kestrels consistent with sexual selection theory Functional Ecology, 12 (2), 307-312 DOI: 10.1046/j.1365-2435.1998.00176.x... Read more »

  • March 28, 2008
  • 12:00 AM
  • 1,521 views

Resurrecting Jackrabbits (Citizen Science Watch: Easter Edition)

by Madhu in Darwin's Bulldogs

In the January 2008 issue of The Oryx, Dr. Joel Berger (of the University of Montana and the Wildlife Conservation Society) published an interesting short article on the likely local extirpation of white-tailed jackrabbits from the Yellowstone region - a cautionary tale about the potential problems of undetected extinctions and their potential ramifications cascading up through food webs. The current issue of the journal is freely accessible, so at least for now you can read the whole article here, and I've put the abstract below the fold. The paper itself has become a cautionary tale for a... Read more »

  • May 9, 2009
  • 05:06 AM
  • 1,416 views

Plagiarism, peer-review, and protecting the integrity of science

by Madhu in Reconciliation Ecology

I am, (it seems) almost constantly reading, evaluating, and passing judgment on, material written by others: not just when I'm synthesizing material for my own papers or blog essays, but as a peer reviewing manuscripts and grants written by colleagues, or as a teacher grading student papers. Comes with the territory of being a professor, or course. As it happens, its that time of year again when... Read more »

  • October 24, 2008
  • 01:36 PM
  • 1,360 views

Lizards Showing Some “Leg”

by Student @ Fresno State in Darwin's Bulldogs

Submitted by Cindy Hua for EvolutionMost of us think that evolution in species take several generations to thousands of years to occur. However, how about if I say in one generation’s time there is a significant change in morphology? Jonathan Losos and his team of researchers from Washington University, St. Louis has found a peculiar lizard that is evolving in a tremendous rate. The brown anole, a Caribbean native lizard, spends most of its day hunting on the ground. One of its main predators is the curly-tailed lizard.As we all know from our evolution class, a chain of islands sets up a great opportunity for parent species to change significantly. Since the Bahamas are home to the brown anole, natural selection will most likely to occur if there is a change in predator population. Losos has tested his hypothesis that with the introduction of more curly-tailed lizards into the main island, the brown anoles are under the influence of selection pressure change (Losos, et. al, 2006). When brown anoles sense danger of increasing populations of curly-tailed lizards, it flees towards trees and stay away from the ground activities for a few generations.After a year’s experiment, Losos discovered that the brown anoles are experiencing a change in leg morphology. In the first six months of his study, the anoles originally had long legs, which enable them to outrun the predators. However, six months later, the survivors had drastically shorter legs, which permit them to hide in narrow crevices and climb in trees. Losos noticed that within a single generation, the anoles went to quick reversals in selection pressure (Losos, et. al). The behavior of the lizards changed, as they prefer treetops than the ground. Here we see natural selection at its finest.Over several generations down, the continuing threat of curly-tailed lizards will force the anoles population to evolve shorter and shorter legs. However, I find it hard to believe that brown anoles can evolve in one generation at such a fast pace. Perhaps through time the longer legged anoles died off and Losos found mostly shorter legged since it was able to survive and reproduce.The quick reversal of evolution by means of selection pressure is quite interesting. The brown anoles started with long legs to outrun its predators but discovered it to be a hindrance as it cannot bend its legs to hide in crevices. It preferred to have shorter legs to save energy and it is easier to live in trees away from the main predator. The anoles do not have a use of long legs anymore so it does not have to evolve back. For example, ostriches, emus, and kiwis all are flightless birds yet they have small wings. Their ancestors were flying species, but, through time, with fewer predators to run away from, they probably foraged on the ground more. Over generations, they most likely could adapt better on land and did not need developed wings for flight. That is why they evolved long, strong legs for running and scratching for food. I believe this is similar to what is occurring to the brown anoles. Their ancestors must have evolved longer legs to run away from predators. however, current species reverted to shorter legs when selection pressure changed. Although I believe the leg lengths did change because of pressure, I find it hard to believe this had all occurred in one generation.Reference:J. B. Losos, T. W. Schoener, R. B. Langerhans, D. A. Spiller (2006). Rapid Temporal Reversal in Predator-Driven Natural Selection Science, 314 (5802), 1111-1111 DOI: 10.1126/science.1133584... Read more »

J. B. Losos, T. W. Schoener, R. B. Langerhans, & D. A. Spiller. (2006) Rapid Temporal Reversal in Predator-Driven Natural Selection. Science, 314(5802), 1111-1111. DOI: 10.1126/science.1133584  

  • September 4, 2008
  • 12:54 PM
  • 1,299 views

Aquatic macroinvertebrate responses to drought

by Student @ Fresno State in Darwin's Bulldogs

A critique submitted by Brett Moore for the Evolution class.Aquatic macroinvertebrates have received and are continuing to receive considerable amounts of scientific attention. The large amount of diversity within macroinvertebrates allows them to be present in almost all natural freshwater environments (Resh and Rosenberg 1984). The evolutionary adaptations that created the diversity within the group also created the great variety of life histories and physiological requirements, which promote the use of macroinvertebrates in scientific studies and biomonitoring, the use of living organisms and their responses to measure the quality of the environment, (Merritt et al 2008).Ecosystem disturbances, whether anthropogenic or natural phenomena such as drought, can create changes in aquatic macroinvertebrate communities by altering habitats and the physiochemical conditions they have adapted to live by. Thus, disturbances can have a large effect on the community structure of aquatic biota. However, many studies have shown that even after a single event disturbance that does not chronically alter habitat, such as a drought and the drying of aquatic habitats, aquatic macroinvertebrate taxa richness can make a rapid recovery (Boulton 2003, Wallace 1990). The fast recovery is most likely the result of the evolutionary history of drought in aquatic environments (Boulton 2003). Boulton and others have done several studies addressing the effects of drought, drying, and intermittent streams on aquatic macroinvertebrates. In Parallels and contrasts in the effects of drought on stream macroinvertebrate assemblages, Boulton observed the effects of drought as an intermittent stream disturbance and the ecological changes that occurred. As riffle habitat dried and the stream turned into isolated pools, species assemblages changed favoring the species more adapted for lower oxygen levels, higher temperatures, and predation on other invertebrates. When flow commenced recovery of the species assemblages began to take place. Recovery rates were rapid for species that had strategies for surviving drying. Two main strategies were identified: 1. Species were adapted for finding refuge. 2. Species had a life history strategy for dry conditions (Boulton 2003). Strategies for finding refuge include being mobile, or being able to bury into damp substrates, while some life history strategies to survive dry conditions include having a terrestrial winged adult stage of the species existent during dry conditions, having desiccation resistant forms of eggs, or having tendencies for downstream drift once flow commences (Boulton 2003, Wallace 1990). Therefore, immobile invertebrates without life histories to survive drying should be heavily effected and take longer to recover from a stream drying disturbance. Several studies have been able to show this. For example, mollusks, which do not have a winged adult stage and are fairly immoblie compared to other invertebrates, have been shown to be among the last taxa to recover following disturbances (Wallace 1990).Boulton (2003) acknowledges the linkages between the history of drought and the evolutionary adaptations of aquatic macroinvertebrates. However, there are still information gaps and questions that need to be answered. Boulton states that most of the data that exists about the effects of drought on aquatic biota is short term, and the lack of pre-impact data exists because studies are opportunistic and droughts are phenomenological events. Understanding the life histories, life cycles, behaviors, and the genetic structure of aquatic macroinvertebrates is also extremely important, however much of the information is still poorly known. Also, several questions still need to be clarified or answered such as: Does frequent drying select for life histories and certain community assemblages? Do the same responses occur across most geographical regions (Wallace 1990)? Once more information becomes available about the evolutionary adaptations of aquatic macroinvertebrates science may have a better understanding of evolutionary processes and what may happen to biota in the future if global climate changes occur. Literature Cited:Andrew J. Boulton (2003). Parallels and contrasts in the effects of drought on stream macroinvertebrate assemblages Freshwater Biology, 48 (7), 1173-1185 DOI: 10.1046/j.1365-2427.2003.01084.xMerritt, R. W., K.W. Cummins, and, M.B. Berg (eds.). 2008. An introduction to the aquatic insects of North America, 4th ed. Kendall/Hunt, Dubuque, Iowa.Resh, V.H., and D.M. Rosenberg (eds.). 1984. The ecology of aquatic insects. Praeger Publishers, New York, NY. J. Bruce Wallace (1990). Recovery of lotic macroinvertebrate communities from disturbance Environmental Management, 14 (5), 605-620 DOI: 10.1007/BF02394712... Read more »

  • April 28, 2008
  • 04:03 AM
  • 1,219 views

Are facial expressions hereditary within a family?

by Student @ Fresno State in Darwin's Bulldogs

[Student post submitted by Swapna Medichetti]
A group of researchers from Israel conducted an interesting study on human subjects and tried to provide evidence for a signature of facial expressions that is supposedly unique within a family. Before this, many studies relating to this have been done on humans. These studies show proof of facial expressions being heritable in an individual while some focus on how different facial expressions are among individuals. But there have been no reports of studies that throw light on different emotional states of people belonging to the same fam... Read more »

G Peleg, G Katzir, O Peleg, M Kamara, L Brodsky, H Hel-Or, D Keren, & E Nevo. (2006) From the Cover: Hereditary family signature of facial expression. Proceedings of the National Academy of Sciences, 103(43), 15921-15926. DOI: 10.1073/pnas.0607551103  

  • September 7, 2008
  • 03:49 AM
  • 1,194 views

Life, The Universe, and Everything Else...

by Student @ Fresno State in Darwin's Bulldogs

Jennie Talbot shares her musings following the class discussion last week in Biogeography (Biol 275).In class we discussed the idea that niches are places that supply a particular organism with all of the resources required for it to thrive. The discussion led to questions regarding how much the niche impacted the species and, in turn, how much the species impacted the niche. For example, a plant species may thrive on the side of a mountain because it is here that the plant can find soil with good nutrients, adequate sun light, and reasonable temperatures. However, as more and more plants colonize the side of the mountain, transpiration will occur at a higher rate, which will produce more moisture in the air and, ultimately cause more rain to fall. The plant’s root system will hold the nutrient-rich soil despite all of the rain. Animals may come and feed on the well-nourished plants and, in turn defecate onto the soil, adding more nutrients for the plants to use. As more and more plants grow in this favorable environment, it is likely that the side of the mountain will get more rain then it did before the plants migrated to this location. Likewise, the side of the mountain may have better soil because of the wildlife that eat the plants. In fact, the wildlife may migrate to this newly colonized region on the mountainside because of the resources available. Therefore, the cycle will continue with more rain, better soil nutrients, healthier plants, and new wildlife. In this way, the side of the mountain, which may at one point have been completely void of life, has become a bustling habitat for multiple species.So then I have to ask the question, “Was earth created for life or did life mold the earth into what it is today?” Of course, people may say, “Yes, the earth was created for life.” Well, Harold C. Urey submits that the earliest atmosphere of earth was composed mostly of hydrogen, methane, and nitrogen with only trace amounts of other elements such as carbon and oxygen. Over time a bunch of chemical reactions occurred (if you want to know all of the reactions, read Urey’s paper) and the earth’s atmosphere changed from being predominantly hydrogen and methane based to being highly oxidized with a lot of free energy created from oxidation reactions. The available free energy made it possible for a few primitive organisms to thrive. From here on out, those small organisms began to colonize earth. Current literature suggests that heterotrophic cells evolved 3.5 billion years ago followed by autotrophic cells (somewhere around 2.7 billion years ago), eukaryotes (2 billion years ago) and then multicellular organisms (Kardong, 2005). Because of the newly formed organisms on the planet, compounds that the earth had not seen yet (like isotopes of sulfur) were made and the compounds that were available already could be molded into something that could be used by another organism (Urey, 1952; Kasting, 1993).So what does all of that mean? It seems to me that when the earth was created, it was completely uninhabitable. Which may mean the earth was not created for life and it is because of life, that the earth is habitable now. When the earth first came to be, there were atmospheric elements that began to interact with one another. From this energy was released, organic molecules were formed and the genesis of life began. At this point in the story, organisms have done nothing to alter the earth. However, with the birth of the first autotrophic cells (and the use of photosynthesis), living organisms began to transform the earth into something that could sustain life. Since then life has molded the planet into what it is today. Of course, it is likely that life has not molded the entire planet (as in, I am not sure that living organisms have any impact on the core of the planet itself…but this is science, so you never know, something could be discovered ☺) and who knows about our impact on the entire solar system. Nevertheless, in terms of niches within our range of exploration on the surface of the earth, it seems that living organisms can have a drastic, sometimes detrimental, impact on their habitats. Image what the world would look like if there was no deforestation or animal poaching. Imagine if the mosquitoes that bite us incessantly were not provided with stagnant water supplies in the rims of old tires and so could not reproduce in new habitats and spread deadly diseases to the inhabitants of those places. What if plumes of dinoflagellates did not blanket the ocean and poison thousands of fish each year. What if asparagus seeds did not float on water? What if fungus did not decompose leaf litter on the forest floor? What would the world look like without millions of species changing the world into a place called home?Okay, so the end of that paragraph was a little cheesy. But truly, without life shaping the planet what would the planet look like? From these thoughts, I believe, at least for now, that living organisms have morphed the earth into what we know today. Without life on this planet, the earth would look completely different.SourcesKardong, Kenneth V. 2007. An Introduction to Biological Evolution. 2nd ed. Boston: McGraw-Hill Companies, Inc., 49-54.J. Kasting (1993). Earth's early atmosphere Science, 259 (5097), 920-926 DOI: 10.1126/science.11536547Harold C. Urey (1952). On the Early Chemical History of the Earth and the Origin of Life Proceedings of the National Academy of Sciences, 38 (4), 351-363... Read more »

  • April 28, 2008
  • 04:03 AM
  • 1,131 views

Evolution by Song

by Student @ Fresno State in Darwin's Bulldogs

[Student post submitted by Darin Alexander]
This is a well written and studied article. This article was about the evolutionary divergence of the Siberian green warbler. The evidence they gather for their thesis is overwhelmingly convincing and they seemed to cover all questions that may come up. They believed and tested that the divergence of song may be the main cause of speciation. This is a highly feasible theory because if you can’t understand someone it is hard to breed with them. (Continues below...)
Background Information: The warbler formed a ring species of interbr... Read more »

  • May 5, 2008
  • 03:34 AM
  • 1,056 views

Evolution of drug resistance in TB

by Student @ Fresno State in Darwin's Bulldogs

Student post submitted by Pritha SinghIn the article “Evolution of Drug Resistance in Mycobacterium tuberculosis: Clinical and Molecular Perspective”, the author Stephen Gillespie describes the clinical circumstances and the molecular mechanisms that are involved in the emergence of drug resistance in tuberculosis (TB). Even after so many years of introduction of very effective drug therapy for TB, the number of people infected worldwide is still increasing due to the development of drug resistance. The basic tool that the medical community has used to control this deadly disease is the combination therapy that uses antibiotics like isoniazid (INH), rifampin (RIF), pyrazinamide (PZA), ethambutol (EMB) and streptomycin (SM).The author first describes the clinical circumstances for the resistance development in Mycobacterium tuberculosis. He states that the reason why drug therapy for tuberculosis is different than the most bacterial infections is due to the long generation time and ability of dormancy in M. tuberculosis. Apart from this, it has a very slow metabolic rate which makes it difficult to target. There are many different populations of the bacterium present within the host. M. tuberculosis may be found in the pulmonary cavities, empyema pus and solid caseous material. The location of the bacterium makes it very difficult for the antibiotics to penetrate or the low pH conditions interfere with the activity of the anti-TB drugs. Thus each of the anti-TB drugs has a unique role in dealing with these different populations of mycobacterium. For example, INH is a drug that is active only against aerobically growing organisms and so it plays a major role very early in the drug therapy against bacteria growing in pulmonary cavities. On the other hand, PZA is a drug only active in low pH conditions thus is used for killing bacilli residing inside the caseous necrotic foci. RIF is most effective in killing the mycobacterium that are metabolizing slowly. Hence, due to the specific roles of these drugs, poor adherence to the drug therapy can result in resistant strains in mycobacterium. Gillespie goes on to explain the molecular mechanism for the emergence of drug resistance. The way the researchers have started to understand the molecular mechanism of resistance in M. tuberculosis is from the action of these anti-TB drugs. The resistance in this bacterium occurs through single step mutations at the chromosomal level. He states that rate at which resistance emerges is different for all the anti-TB drugs which could be calculated by using the mutation rate. Mutation rate rather than mutation frequency is used to calculate the rate of resistance because calculating frequency has a risk of recording mutation per cell division. However, mutation rate is more apt as it records the proportion of the mutant cells. The author provides an equation and hypothetical calculations for resistance rate in the mycobacterium which suggests that even a small deviation from the standard drug regimen may lead to the emergence of resistance in a TB patient. To describe the development of drug resistance in M. tuberculosis, the author talks about two anti-TB drugs: streptomycin (SM) and rifampin (RIF). A point mutation in rpsL gene results in high level of resistance to SM which can be categorized into restrictive and nonrestrictive mutations. Restrictive mutations are associated with an attenuation of virulence, whereas nonrestrictive mutations are not. He lists various clinical studies that show that resistant strains were equally divided between restrictive and non-restrictive mutations. However, the author does not explain how SM works on the bacterium or how the mutation in a specific gene leads to resistant strains which could have helped in better understanding of this section. Moreover, he does not mention an additional mutation that takes place in rrs operon which could also lead to drug-resistance. The mycobacterium strains that are resistant to RIF have a mutation on the beta subunit of rpoB gene encodes for DNA-dependent RNA polymerase. Experimental studies have shown that more than 70% of the RIF’s mutations are restricted to the rpoB gene. He also mentions the study conducted by using the model of guinea pigs that were infected with M. tuberculosis in which katG gene was inactivated. These studies showed that the virulence of the strains was far less than the parent strain. However, the virulence was restored when katG gene was reintegrated in the genome. The author does a fair job in stating the clinical studies, however does not mention anything about the drug mechanism. KatG gene encodes for enzymes that are involved in mycolic acid biosynthesis but there was no mention of how mutation in katG gene is what leads to the INH resistance. Lastly, the author mentions about human studies of resistance emergence. He mentions a report in which a brother and a sister suffered multiple drug resistance due to non adherence to the drug therapy. This case provides the evidence that variation in biological fitness has an affect on outcome of the therapy. In this study, the bacterium in one case showed multiple-drug resistance (MDR) whereas in the other case, it was completely susceptible which suggested that fitness deficit was directly related to the difference in susceptibility. However, Gillespie also mentions that multidrug-resistant M. tuberculosis strains with identical susceptibilities have different in vitro fitnesses. He provides data of a study conducted on an infected human female that suggests that changes occur on passage in humans. Since initially resistant strains have a fitness deficit, transmission of the organism in a group of immunocomprised people may allow the bacterium to adapt and be transmitted while adapting. This also agrees with previous studies that show MDR numbers have increased in immunocomprised patients. The author ends his articles by stating that these molecular and clinical studies have shown that resistant organisms over time can become fully virulent. Thus to prevent the multi drug resistance tuberculosis, steps must be taken that patients are effectively treated. Drug-resistance is a major threat to human population and to stop these numbers from rising, it is important to understand the mechanisms of resistance development in this organism. Treatment with internationally approved regimens is very effective in preventing the resistance development. This is due to the fact that combination of drugs involved in the therapy makes it very unlikely for spontaneous mutations to occur to all the antibiotics involved. Inadequate treatment of tuberculosis or treatment with only one type of drug can lead to resistant strains. When these strains that are resistant to single agents are exposed to the combination drug therapy, the effectiveness of the drug therapy is depleted which further leads to multiple-drug resistance. The author of this article Stephen H. Gillespie is a Professor of Medical Microbiology at University College London. He has done a lot of research in the treatment and diagnosis of tuberculosis and other respiratory infections. The author provides plenty of reference articles and studies to refer for further clarification for the reader. He backs up his statements with evidence collected from various research studies. However, the author’s use and interpretation of the evidence was unclear to me in many sections. To wrap up, my opinion of this article is that it was very difficult to follow at times and the author should have included some basic information about the drug action on the mycobacterium before talking about the gene mutations that lead to the drug resistance.Reference: Gillespie, S.H. (2002). Evolution of Drug Resistance in Mycobacterium tuberculosis: Clinical and Molecular Perspective. Antimicrobial Agents and Chemotherapy, 46(2), 267-274.... Read more »

Stephen Gillespie. (2002) Evolution of Drug Resistance in Mycobacterium tuberculosis: Clinical and Molecular Perspective. Antimicrobial Agents and Chemotherapy, 46(2), 267-274. info:PMID/11796329

  • November 2, 2008
  • 11:31 AM
  • 1,025 views

My Inferiority to Scrub Jays

by Student @ Fresno State in Darwin's Bulldogs

Rudy Cerda confesses for the Birds & Reptiles class. Elsewhere, Claire Go has blogged about the same study!As much as I like to think that I plan according to future needs, such as time management in order to write papers, study for exams, and even complete this blog, I know I can only operate under pressure. However, when planning for “essential” needs such as food or snacks, I save the best for last or at least hide some away in case I may need or want any later. For example, I’ll always leave my favorite flavor of candy last because I want that flavor to linger for awhile, or I’ll eat the crust first on a slice of pizza because I’d rather wait to take in the gooey, cheesy goodness on the other side of the piece... but enough of my planning for less than crucial things. Aphelocoma californica, better known as the western scrub jay, may exhibit planning for the future in perhaps a more critical way than I do.According to the Bischof-Köhler hypothesis, only humans are able to disconnect themselves from their current motivation and plan for the future. Apparently other animals do not have crystal balls to predict their future needs and any future-oriented behaviors are due to either patterns of fixed actions or prompted by current motives. There have been previous studies involving rats and pigeons that have that have only supported the Bischof-Köhler hypothesis by the animals solving tasks involving the future, however, the “future” was only a very short time period. Also, primates have also shown the ability to take actions based on future consequences; however, the motives or reasons for the actions have not been differentiated.Scrub jays are relatively abundant around campus and I frequently observe jays bouncing around with nuts in their beaks. Every so often I’ll see one that is particularly sneaky and decides to stash its food away as if its saying, “You’re not going take this from me,” or preparing for the budget cuts around campus (or perhaps they can sense the inevitable collapse of the economy!) that may take away their beloved seeds. Raby et al also noticed this behavior in western scrub jays and hypothesized that the jays store food based on anticipation of future need. They predicted that the jays would do this in an area in which they have learned they will be hungry and by storing a particular food item in a place where they know it will not be available.To test this hypothesis, a total of eight western scrub jays were placed in two different compartments on alternate mornings for six days. In one compartment they were given breakfast and the other they were not. After this training, the birds were given food unexpectedly given food to either eat or store in the evening. If the birds were capable of planning for the future, they would store relatively more food if they were in the compartment in which they were not given breakfast because they would anticipate being hungry the next morning… psychics! And the results displayed their fortune-telling abilities as they stored significantly more food (more pine nuts than powdered nuts) in the compartment in which they had not received breakfast.To ensure the hoarding of the pine nuts was not associated to a specific compartment, two different types of food were given; a specific food was given in a specific compartment and both types in a third compartment. If the jays had a preference of a certain food they would store more of the “other” food rather than the “same” food when offered to store the food away. The results supported the hypothesis of preferential storing food.Often I find it hilarious when I see a jay hopping around with something in its beak, it hides the food and about 30 seconds later it’s looking for the food it just sneakily stashed away! Some planning if it can’t even remember where it put its food! In the Raby study, it was stated that the birds were slightly hungry, so perhaps those greedy jays around campus are just playing dumb because they aren’t hungry at that moment in order to fool everyone and plot their takeover of campus and my apartment complex! Well, it’s nice to know that my planning skills may be significantly inferior to a scrub jay’s.Reference: C. R. Raby, D. M. Alexis, A. Dickinson, N. S. Clayton (2007). Planning for the future by western scrub-jays Nature, 445 (7130), 919-921 DOI: 10.1038/nature05575... Read more »

C. R. Raby, D. M. Alexis, A. Dickinson, & N. S. Clayton. (2007) Planning for the future by western scrub-jays. Nature, 445(7130), 919-921. DOI: 10.1038/nature05575  

  • December 3, 2008
  • 05:33 AM
  • 1,018 views

Modeling the emergence of multi-drug resistant TB hot zones

by Student @ Fresno State in Darwin's Bulldogs

Rebecca Freeman submitted this essay for the Evolution class.According to the World Health Organization (WHO), a “hot zone” is an area with >5% prevalence (or incidence) of Multi-Drug Resistant Tuberculosis (MDRtb). Sally M Blower and Tom Chou have been using a mathematical method to track the emergence and evolution of multiple strains of drug resistant tuberculosis, but they have now developed a new, more complex mathematical model. Before this model, there was only a two strain model, meaning it was only relevant to individuals that can be infected with a wild type pansensitive strain or a drug resistant strain, but there are many more strains then this. There are a resistant strains only to one drug and some resistant to multiple drugs. This means there is a multitude of strains in these hot zones and there was a need for a better way to track this (Blower and Chou 2004). Blower and Chou realized that a more complex mathematical model is necessary to capture the complexity of the epidemiology of the hot zones, and the evolution of hot zones was very unclearUnderstanding drug resistance is important to understanding the, and Blower and Chou explain the evolving of resistance very well. They give three processes that are involved in generating drug resistance: Transmission of drug resistant strains to uninfected individuals, which is transmitted resistance; Conversion of wild pansensitive cases to drug resistant cases, which is acquired resistance; finally, cases where they have drug resistant strains and it becomes resistant to more antibiotics during treatment, which is amplified resistance. What everyone has had to do in the past is just study acquired and transmitted resistance, and now with the new model, they can incorporate amplification resistance. This was a big problem because it has been shown that inadequate treatment of DRtb can result in the amplification of drug resistant strains, which may be an important process of MDR epidemics (Blower and Chou 2004). So this is where Blower and Chou came in. They created a model, the call the amplifier model, that enables the tracking of emergence and evolution of MDR strains, the transmission of these strains and the amplification of these strains during repeated episodes of treatment.Blower and Chou are really studying the effects of inadequate treatment programs, and how this may lead to a higher prevalence in MDRtb. One problem that this research cannot completely take into account yet is the transmittance ability of MDRtb compared to pansensitive tuberculosis. This is an area that is hazy right now, and so this cannot completely be incorporated into the model. Amazingly, they have measured a general fitness of MDRtb vs. pansensitive tuberculosis, by calculating the treatment fail rates and treatment cure rates of the each category of strains.The authors were very clear with the purpose of the model. Even though the mathematical model is very complex, the idea and how they explain it is easily understandable. They use R0 to stand for the average number of secondary cases caused by one infectious case in a population where treatments are available. Their model breaks this up into four categories of strains: The wild type pansensitive [R0(1)], which is sensitive to all drugs; Pre-MDR [R0(2)], which is sensitive to one of the main drugs used to treat tuberculosis; MDR [R0(3)], which is resistant to both of the main treatment drugs; and post-MDR [R0(4)], which is resistant to both of the main antibiotics and others as well (Blower and Chou 2004). With the information gathered from over 30 years of date they constructed likely evolutionary trajectories of hot zones, and with this they also took into account low cure rates vs. high amplification probabilities in many areas. They also tried to incorporate which strains are more transmissible, but as I said before this was not really possible with their model and there was a large degree of uncertainty.The results of their model matched the WHO predictions well, but there were some distinct differences, and I think these differences are what make this research so important. By using all for types (R01-4) they found great variability in incidence and prevalence. When treatments were originally started strains of pre-MDR strains emerged quickly, so incidence and prevalence of pre-MDR strains increased, and this subsequently led to possible amplification of resistance and MDRtb epidemics in certain areas. The question is: Why certain areas and not others? This question is explained by Blower and Chou. Interestingly, areas with bad treatment programs do not necessarily have a really high incidence of MDRtb, it has stayed pretty steady at a 5%-14% (Blower and Chou 2004). This to me seems like an argument that MDRtb is not as easily transmissible, because its rates overall have stayed pretty low, but there was no significant evidence for this. The WHO predictions state that a >5% prevalence OR incidence in MDRtb equals a hot zone. Blower and Chou found the mathematical relationship between MDR prevalence and incidence. MDR prevalence can be three times greater then MDR incidence. They used the results to evaluate the hot zones on prevalence or incidence. If it is by incidence then only 20% of those areas would be considered hot zones and 51% if criterion is prevalence (Blower and Chou 2004). I see this as an argument for the fitness of MDRtb to be very high and transmissible ability to be lower, because there are less new cases, and more cases that have just become more resistant.When looking at the four strains the hot zones had a much lower R0 for pansensitive strains (median=.82), which suggests that the wild type strain should be slowly eradicated. The R0 for the pansensitive strains in non-hot zones were all above 1 (median=1.39) Looking at the rate of detection of cases and treatment rates in hot zones versus non-hot zones it is 55% to 25% (Blower and Chou 2004). This shows that places where they have control programs were successful at fighting pansensitive strains but ironically it created more MDRtb strains, making it more likely to become a hot zone.The importance of this research is that they have figured out that the difference between incidence and prevalence rates is significant enough to change the view of an area as being a hot zone or not. Their research looks at many factors that go into the evolution of these hot zones. Out of the many factors they actually saw that case detection and treatment rates were the most important factors. They came to this conclusion because if case detection and treatment rates were low, and the amplification was high, it still did not generate a hot zone. Vise versa, if the case detection and treatment rates were high and the amplification rates were low; it was likely to become a hot zone. The point is that these areas with high case detection and treatment rates should not increase these rates unless high cure rates are achieved first. Blower and Chou have created a model that has multiple dimensions and can help the WHO in the future to prevent hot zones from popping up in high risk regions. The WHO already had a model for this but it was nowhere complex enough to correctly calculate prevalence and incidence of MDRtb, and how their mathematical relationship.Reference: Sally M Blower, Tom Chou (2004). Modeling the emergence of the 'hot zones': tuberculosis and the amplification dynamics of drug resistance Nature Medicine, 10 (10), 1111-1116 DOI: 10.1038/nm1102... Read more »

  • November 7, 2008
  • 12:36 PM
  • 991 views

When a Cutthroat meets a Rainbow

by Student @ Fresno State in Darwin's Bulldogs

Submitted by Christopher Clapp for the Evolution class.The introduction of a known species of rainbow trout into a native population of cutthroat trout and the consequences of their contact within their environments is the focus of this study. The interaction of these two species has resulted in their study of subsequent progeny shows hybridization of the two, and thus a decline of the natural populations of cutthroat trout. The implications of this hybridization will show throughout subsequent generations, considering what is known of the native species. Metcalf uses mitochondrial and nuclear markers to determine the levels of crossing of the two species based on the nature of homozygous or heterozygous allele category. These populations of hybridization were evaluated due to the known history of the streams being studied. Trout being separated by natural geographic restrictions such as natural waterfalls or by human chemical treatment conducted in the past forms for a basis of evaluation.The successful progeny of hybridization between the two locations is evident; however there are differences between the chemically treated streams and the naturally restricted. Interestingly enough, results show that there is a trend of the cutthroat nuclear trout alleles being more prevalent beyond the upstream barrier as expected. The mitochondrial alleles were more prevalent within the hybrid or rainbow species within the areas that direct contact has been introduced within the natural barrier stream. Our study supports the notion that natural waterfall barriers provide a refuge for pure native cutthroat trout genomes across their range (Metcalf et al 2008). In the Cony Creek population, which was subject to chemical treatment in 1984, the nuclear markers were more prevalent within the cutthroat species. This bias toward the pure cutthroat is speculated to be due to the chemical treatment of the streams to eradicate the rainbow trout populations amidst restocking the cutthroat population (Rosenlund et al. 2001). Why is the case? The allele frequency distributions and disequilibrium values suggest that hybridization has been underway for longer in Cony Creek than in Graneros Creek according to Metcalf, et al (2008). I seem to feel that introducing a chemical treatment to an environment that focuses directly on one specific species allows for a re-founding of the native species. However, there findings show the invasiveness nature of the rainbow species. Over time the cutthroat nativity would be eradicated regardless of natural barrier or chemical treatment. This poses two major problems for the environment with regard to the natural species, and the changes of fish populations within streams. The introduction of new fishes for conservation strategies not only directly affect the native population, it affects the ecosystem among other animals within the environment as well. If an aggressive population of trout that is more successful than the native, the impact on resources for the community will also be affected; the environment will be in disequilibrium.We seem to have two intrusions of the human hand into an environment, one for the introduction of the rainbow, and one to eradicate the rainbow trout species. The study shows that there is greater fitness among the hybrids. The cross between a rainbow trout female and a cutthroat male resulted in a shorter time to hatching and the progeny had a faster growth rate and a greater abundance of yolk at hatch and emergence than the hybrids of the reciprocal cross (Hawkins and Foote, 1998). Nevertheless, the two species form a system of fertility to study the hybrid selection based on natural selection and/or the effects of human based effects in the form of conservation strategies. What is this to say for the natural selection of the hybrid species or the difference between the two, and what are the effects of the introduction on the environment? Historically fishless lakes and streams have been associated with declines in amphibians, changes in invertebrate communities and changes in nutrient cycling (Knapp and Matthews, 2000). However, there is always something to be learned from the development of a new species. The selection and fitness over such a short amount of time is interesting to evaluate within the two species.It seems to be that the rainbow trout are invading the natural species of cutthroat, and have an effect on the native species. Why are the rainbows so successful at invading this species? What are we to learn of the intrusion of populations by human hands? Either way, I agree with Metcalf in the capacity that the evaluation of the new hybrid species will give insight into long-term conservation strategies. It seems that if we limit the studies and only hold them as individuals there will always be contradiction of the results. Conservation methods and steps may be a bit naïve if you only consider one method to achieve one result. By not considering the whole picture, we are increasing our opportunity cost, and thus the potential for loss.References:Denise K. Hawkins, Chris J. Foote (1998). Early survival and development of coastal cutthroat trout (Oncorhynchus clarki clarki), steelhead (Oncorhynchus mykiss), and reciprocal hybrids Canadian Journal of Fisheries and Aquatic Sciences, 55 (9), 2097-2104 DOI: 10.1139/cjfas-55-9-2097Roland A. Knapp, Kathleen R. Matthews (2000). Non-Native Fish Introductions and the Decline of the Mountain Yellow-Legged Frog from within Protected Areas Conservation Biology, 14 (2), 428-438 DOI: 10.1046/j.1523-1739.2000.99099.xJ. L. Metcalf, M. R. Siegle, A. P. Martin (2008). Hybridization Dynamics between Colorado's Native Cutthroat Trout and Introduced Rainbow Trout Journal of Heredity, 99 (2), 149-156 DOI: 10.1093/jhered/esm118Rosenlund BD, Kennedy C, Carnowski K. 2001. Fisheries and the Aquatic management of Rocky Mountain National Park. (US Dept. of the Interior).... Read more »

  • April 8, 2008
  • 03:03 AM
  • 974 views

The Ecological Strategies of Sea Turtles

by Student @ Fresno State in Darwin's Bulldogs

Student posting by Rebecca Bellamy
Since the Triassic, sea turtles have not changed a great deal. About 200 million years ago, the common ancestor to today’s Chelonians developed an “armored tank” body form, enclosing its body inside a tough shell as a mode of defense from large toothed predators. This was one of the early steps that led to the evolution of the sea turtle. The development of this hard encasing was achieved by many other anatomical changes. Many vertebrae from the trunk region were done away with and the ribs were no longer attached to the sternum. Because of th... Read more »

John Hendrickson. (1980) The Ecological Strategies of Sea Turtles. American Zoology, 597-608.

  • October 26, 2008
  • 09:17 PM
  • 972 views

Socially learned foraging behaviors in wild black bears

by Student @ Fresno State in Darwin's Bulldogs

Andrew Mora offers a review of the Biology department seminar by Rachel Mazur.The American Black Bear, Ursus americanus, is currently the only species of bear in the state of California. In a fascinating presentation by Rachel Mazur, pictures and videos were used to depict the beauty of these bears in their natural and not so natural environments; the latter being bears foraging for food in developed areas of the national parks including getting food out of trash cans, cars, etc.According to Mazur, these bears are especially hungry during the months of March and April. During this time, a bear is either termed by Mazur to be a wild foraging bear, which consists of eating grasses, roots, insects from shredding logs etc., or they can be food conditioned bears, which consist of getting their nutrition from developed areas, or humans.Research by Mazur finds that bears have traits for social learning and the most critical times of a bears learning process is during the first year when they are in constant contact with their mother (Mazur, 2008). Three separate hypotheses were compared to describe how these bears are learning to become food-conditioned to developed areas. The first is that bears inherit these behaviors from their mothers and can be predicted (Mazur, 2008). The others include bears learning individually (that is, without the help of the mother) and transmitted learning from sow to cub (Mazur, 2008).The methods used for this experiment were efficient in that homogeneity was taken into consideration. Therefore five variables were taken into consideration including park, sow identity, sow behavior, rearing method and cub outcome (Mazur, 2008). The two national parks which Mazur encouraged everyone to visit include Sequoia National Park and Yosemite National Park. From showing clips of a movie on this research, it was evident that many years of hard work by numerous staff was done to work with these bears and monitor their statuses.Mazur stated that she was very pleased with the results that they came across. An easy to read table of her results shows the number of sows that they started with (23 food conditioned and 9 wild), the rearing methods of these sows (rearing in wild or food-conditioned rearing), and the outcome of the cubs once separated from their mothers (Mazur, 2008).Conclusions made by Mazur asserted that rearing method had a highly significant effect on the cub outcome (Mazur, 2008). If a cub was reared food-conditioned, it was much more likely to be food-conditioned once separate from its mother. That being said, the last hypothesis stated by Mazur was seen to be the most accurate: that bears become food-conditioned through social learning.In both seminar and paper, Mazur stated that there are numerous implications for the work that has been done. She posed a question to the room regarding the bear’s possibility of creating culture and even tradition in our national forests with these new food-conditioned characteristics (Mazur, 2008). What I found beneficial in this work is the implication that food-conditioning in developed areas in our national forests do not necessarily imply adaptive strategies of these Ursus americanus, but may very well be falling into an ecological trap (Mazur, 2008). I also found it interesting for her to note that science and management have recently become less taboo as a pair in the scientific world.Reference:R MAZUR, V SEHER (2008). Socially learned foraging behaviour in wild black bears, Ursus americanus Animal Behaviour, 75 (4), 1503-1508 DOI: 10.1016/j.anbehav.2007.10.027... Read more »

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