Sunday, May 01, 2011

UC Davis, home of "Explosive Evolution"

A semi quick one here.  I am writing this in part because it is really a lot of fun to be at UC Davis with all the excellent evolution and ecology stuff going on here.  Some links for those who might be interested in learning more about Evolutionary studies at UC Davis include:
There is more but that is a good start.  Anyway a recent press release from Davis caught my eye in part because I know the people involved and also in part because I was unaware of the details of what they have been working on.  The press release is titled "Explosive Evolution in Pupfish" and discusses some interesting research by a PhD student Chris Martin and his advisor, my colleague Peter Wainwright.  The work was published in Evolution and is entitled: "TROPHIC NOVELTY IS LINKED TO EXCEPTIONAL RATES OF MORPHOLOGICAL DIVERSIFICATION IN TWO ADAPTIVE RADIATIONS OF CYPRINODON PUPFISH" (DOI: 10.1111/j.1558-5646.2011.01294.x).  Alas it is not OpenAccess, but the paper is available on their lab web site here.

The work is a bit out of my arena, and I suppose I could critique the press release a bit, but I won't right now. As a side note, I should mention I really love pupfish so that also caught my eye, and I have occasionally tried to convince Chris to look at the microbes in pupfish.  
Anyway, rather than bore people with my thoughts, I thought it might be nice to post some comments I got from Chris about the paper.  I got these is a series of emails and though they are a bit out of context, I am just going to post them here: 
Note that the press release is a bit confusing: there are other scale-eating fishes (has evolved at least 14 times independently), but this is the only scale-eating pupfish (and only scale-eater among all 1500 atherinomorphs). 
#2: Pupfish are indeed named after puppy dogs for their playful swimming behavior!
#3: I think the most exciting thing about this system is that it presents the opportunity to study the origins of ecological novelty in a very recent radiation (possibly as young as 8,000 years if we go by geographic dates of the lakes). This study leaves many outstanding questions that I hope to address in my future research.

For example, why does exceptional adaptive radiation occur on these two islands and nowhere else in the Caribbean? Is this due to lack of sampling, is there something unique about these two environments, or is there something unique about the founding populations in these two cases? Both lakes are large, isolated, productive environments with only 1 or 2 other competing fish species and this is surely part of the story. But, there are many other large lakes in the Caribbean, often with very similar fish communities. Further, note that the other competing fish species have not diversified at all: is this due to their time of arrival or is there something special about pupfishes? I'm currently planning to do broader sampling of pupfish populations and lake environments across the Caribbean to address these questions.

Second, what factors actually drive such dramatic rates of morphological diversification? I have just returned from a trip to San Salvador Island where I setup four field enclosures and added juvenile pupfish to estimate a fitness landscape for jaw morphology in this environment. Juveniles were F2 hybrids of the three species raised in the lab here at Davis in order to sample from the full spectrum of phenotypic variation. I will be returning in July to collect this experiment and I do hope my enclosures and some fish survive! This study should provide an estimate of the strength of selection on existing phenotypes as well as potentially unfit intermediate phenotypes.

Finally, why have different sets of resource specialists evolved in very similar environments? In particular, why has a specialized scale-eater failed to evolve in Mexico - there are obviously scales to feed on and the fish densities appear comparable. Scale-eating has evolved independently many times, but why don't all fish communities contain scale-eating specialists?

Anyway, going to try to write more about Evolutionary studies at UC Davis in the future. I am always amazed at how much interesting work there is here.

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