Previous work by Cox and Calsbeek has shown that ovariectomized lizards grow faster and survive longer than lizards with intact ovaries. Ovariectomized lizards also develop larger fat bodies, and a reasonable explanation is that it is the greater fat that these lizard accumulate that allows them to survive better over the winter. To test this hypothesis, the authors experimentally removed fat bodies from some lizards and not others. They found that this treatment had no effect on survival, thus disproving the hypothesis. In other words, removal of the ovaries both increases fat body buildup and survival, but the two phenomena are not related, a nice demonstration of the importance of experimental manipulation to understand disentangle correlation from causation and elucidate physiological mechanisms.
Author: Jonathan Losos Page 99 of 133
Professor of Biology and Director of the Living Earth Collaborative at Washington University in Saint Louis. I've spent my entire professional career studying anoles and have discovered that the more I learn about anoles, the more I realize I don't know.
Anolis punctatus. Photo from http://www.flickr.com/photos/32688820@N02/3121948727/sizes/m/in/photostream/
Anolis punctatus is one of the coolest looking anoles of South America, which is saying a lot. It is widely distributed throughout South American rainforest habitats, but has been relatively little studied. Last night Ivan Prates exhibited a poster reporting the results of a phylogeographic analysis of the species from Amazonian and Atlantic forests. The study is impressive in its scope and sampling, and finds a high degree of genetic divergence throughout the species’ range, paralleling results for another Amazonian species group, A. chrysolepis and relatives. In addition, the Atlantic forest populations are nested within Amazonian populations, suggesting that dispersal occurred from the Amazon to the Atlantic. Molecular calibration puts the date of the dispersal at ca. 3 million years ago, which would correspond with vegetation reconstructions that suggest the forests were connected at that time.
In addition, the study contained samples of the extremely little known horned anole of the Amazon, A. phyllorhinus, which places this species as the close relative of A. punctatus, and hence distantly related to the Ecuadorian horned anole, A. proboscis.
Anolis marmoratus from Guadeloupe. Photo from http://www.karibische-anolis.de/
It was a colorful morning here in Ottawa. First, Julienne Ng reported on her work on the causes and consequences of dewlap color evolution in Anolis distichus in Hispaniola. This species is renowned for the variety of dewlap colors–primarily whites, yellows, and oranges, but also red–displayed by populations throughout the island, and a phylogeographic analysis indicates that different dewlap colors have evolved multiple times. Julienne demonstrated that a correlation exists between environmental variables (e.g., precipitation) and dewlap color and brightness; these variables explained much more of the variation than did geographic distance separating populations or the degree of genetic differentiation. She then asked whether differences in dewlap color serve to reproductively isolate populations. She tested this hypothesis by sampling four transects across areas whether dewlap color changes over a short distance. She found that in one transect, the two populations differing in dewlap color were highly differentiated genetically; in the other three cases, by contrast, the populations were not at all differentiated. This finding is potentially important, as dewlap color is often used to describe different species; the results indicate that populations with different dewlap colors may not be strongly isolated genetically.
Later in the morning, Chris Schneider reported on studies of the genetic determinants of color in the wildly variable Guadeloupean species, Anolis marmoratus. This species exhibits so much variation that 12 subspecies have been described from Guadeloupe and nearby islands. By illumina sequencing, Schneider has found 250 fixed differences between populations differing in color–one with red heads, the other with blue. Preliminary analysis suggests that at least 60 protein-coding genes are involved. This work is a promising first step in identifying the genes underlying color differences in anoles.
Several years ago, Calsbeek and Bonneaud published a provocative paper in which they showed that females preferentially used sperm from large males to produce male offspring and from small males to produce females. An obvious question is: how do they do this? Anoles are known to have sperm storage and to be able to produce fertile young many months after mating, but how can females “choose” which male’s sperm to use to fertilize offspring? Presumably, in some way the female would have to keep track of which sperm came from which male, and what the phenotypic attributes are of those males.
Dartmouth graduate student Katie Duryea reported ongoing work aimed at addressing these questions. Taking a two-pronged approach, she is looking at the genetic basis underlying reproduction in anoles. First, she is examining gene expression in the reproductive tract of female Anolis carolinensis, comparing recently mated and unmated individuals. Preliminary results revealed more than 5000 genes that appear to be upregulated, based on transcript abundance, in the females. Examination of gene ontologies reveals interesting patterns of what types of genes are upregulated, with apparent similarities to similar work in Drosophila. Second, taking a candidate gene approach focusing on serine proteinase genes, Duryea is comparing differentiation between A. carolinensis and A. sagrei. Preliminary results for one gene show a relatively large number of synonymous changes, suggestive of the action of natural selection.
Clearly, this work is in its early stages, but results so far are tantalizing and provide another example of how the anole genome will prove useful in addressing outstanding questions in anole evolution and behavioral ecology.
In an epic undertaking, Powell and Henderson have edited a monograph compiling the species occurrence of reptiles and amphibians on more than 700 Caribbean islands. In addition to the species lists, information on island size and location is provided, and introduced and extinct species are noted.
This work, an update on several previous such lists, will be enormously useful for biogeographers, ecologists, evolutionary biologists, and conservationists, among others, and the editors and authors are to be heartily thanked and congratulated for their efforts.
Now, an anole bone to pick.
Day’s Edge Production in full swing
The guys at Day’s Edge Productions keep on chugging along. Their latest offering is the first video report from their Italian island lizard project, studying the incredible variation of wall lizards found on tiny Spanish islands. What makes this video worth checking out for anolistas is the incredible abundance and audacity of the lizards, which crawl right over the actors as the camera rolls. Anyone ever seen anoles that daring?
Last year was a banner year for anoles. As Xavier@evolutionistX tweeted at the end of the Norman, OK Evolution meetings: “The star of #evol11: Anolis lizards. They won both Fisher’s and Dobzhansky awards, would like to invite them to a celebrity party @NYC.” And who could blame him? The prestigious Dobzhansky and Fisher Awards both went to workers studying anoles, as did three of the four Young Investigators Prizes. And there were a slew of other excellent anole talks (reported on these pages last year; start at this post and work backwards, or search on “Evolution Meetings”). David Hembry summarized the meeting well on Nothing in Biology Makes Sense: “I confess, I didn’t go to the Evolution meetings for three years. I missed Minnesota in 2008 due to fieldwork, Idaho in 2009 due to illness, and Portland in 2010 due to the EAPSI. When I “returned” in 2011 in Norman, it was like everybody had switched to working on anoles and sticklebacks!” (see the rest of David’s insightful observations on this point below).
But can anoles do it again in this year’s meeting , slated to begin on Friday in Ottawa? You can rely on Anole Annals to be on hand to provide the play-by-play coverage from the spectacle of the opening ceremonies to the climactic closing mixer. And fear not: though not the grand slam of last year, anoles again will bring home some medal.
Here are the talks. Unfortunately, authors are not listed, but you can get all program information at the meeting’s program mobile app website:
Photo by Avery Locklear at http://travel.nationalgeographic.com/travel/traveler-magazine/photo-contest/2012/entries/141546/view/. From the National Geographic Traveler 2012 photo contest.
Like they always say, it’s important to take time to smell the bananas.
Avery Locklear provides the back-story: “I saw the banana flower from a distance and approached it. Then I found the anole resting on it, sitting content. I stood there for a few minutes as it continued to explore the banana flower.
I have so many memories of anoles from when I was younger. I always called them chameleons until several years ago, I looked them up and found more information about them. My grandmother, who lives in Florida, would sometimes find them in the house and would catch them so she could set them free. I always liked to have a look at them before she let them go.
I have lots of photos of them as they are everywhere in Florida.”
Anolis concolor from mangroves on San Andres island. Photo by Lee Fitzgerald
Almost all Caribbean anoles are descendants from a single colonizing species, whose descendants now occupy all of the Greater Antilles, the Lesser Antilles south through Dominica, and many other islands. Almost all of the remaining species are members of the roquet clade, occupying the southern Lesser Antilles and descended from a South American colonist. As we all know, these species have been extensively studied.
But colonization of Caribbean islands has occurred more than just these two times. Some other islands have been colonized by different colonists. None of these invasions has led to much in the way of evolutionary radiation and these species–in each case the only anole on the islands they occupy–have been little studied. We’ve previously discussed one such colonization, A. lineatus on Aruba and Curaçao. In addition, islands in the Pacific (yes, the Pacific!) have twice been colonized, leading to A. agassizi on little known Malpelo and A. townsendi on Cocos Island (incidentally, the island said to have beeen the inspiration for Isla Nublar in Jurassic Park).
And, finally, there are the presumed sister taxa, A. pinchoti and A. concolor, on the Colombian islands of Providencia and San Andrés. A smidgeon of research has been conducted previously on their ecology, and now a new paper in the South American Journal of Herpetology has examined their morphology. Calderón-Espinosa and Barragán Forero measured museum specimens of these species and compared them to published data on a variety of other Caribbean anoles. They found that neither species is a good match for any of the Greater Antillean ecomorphs, but that they are most similar to trunk-ground or trunk-crown anoles. By comparison, anoles of the Lesser Antilles are also most similar to these two ecomorphs. Anolis concolor attains an intermediate body size, similar to Lesser Antillean species that occupy islands on which they are no other anole species. By contrast, A. pinchoti is smaller and more similar to the smaller Lesser Antillean species on two-species islands.
Anoles are renowned for their convergent evolution. Further comparison of the many cases in which anoles have colonized relatively small islands should prove interesting.
M. L. Calderón-Espinosa and A. Barragán Forero (2011). Morphological Diversification in Solitary Endemic Anoles: Anolis concolor and Anolis pinchoti from San Andrés and Providence Islands, Colombia South American Journal of Herpetology
Lunchskins are reuseable sandwich bags. Great idea? Or a green, scaly mess?