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.
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.
Rings and syringes for gastric lavage.
With only two weeks left in El Yunque, Puerto Rico, the two projects that Travis Ingram and I are doing will soon come to a close. Travis has already written about one project, the enclosure experiment. The second is a diet survey of six species (Anolis evermanni, A. stratulus, A. cristatellus, A. gundlachi, A. pulchellus, and A. krugi) that are sympatric in the area around where we are staying. The goal is to quantify diet overlap between these species. To obtain the stomach contents, we use a nonlethal method known as gastric lavage. I chose this method unsure of how it would turn out because, before this trip, Travis and I had had very little practice performing gastric lavage. My hope was that we could take this technique that we had read about and practiced a few times in the lab and become good enough at it to do it potentially hundreds of times in the field.
**UPDATE (July 17, 2012): Thanks to all the folks who have contributed literature – it’s a huge help! We’ve made good progress towards our first goal of obtaining all original descriptions of Anolis species. Here’s an updated “Most Wanted List.” We’re pretty close to knocking them out….
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Anole bibliophiles and reference collectors,
The Anoline Lizard Specialist Group has a favor to ask, and one to return as well: We need your help assembling a digital reference library for Anolis literature.
Our goal? – To compile PDFs of every published piece of literature relevant to the taxonomy or conservation of Anolis lizards.
The reason we’re doing this is to aid in the IUCN Red List assessment process for anoles. Having ready access to this literature dramatically simplifies the task of conducting and reviewing species assessments. Also, as the IUCN’s “Red List Authority” for Anolis lizards, the ALSG will soon maintain an authoritative list of currently recognized anole species. Ready access to the anole taxonomic literature will facilitate this as well.
We already started this process, and we’ve made a good dent. Like many of you, we’ve been amassing anole PDFs for years (albeit sometimes haphazardly). We recently
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.
While conducting field work in the Dominican Republic, we recently took a morning off to go for a hike to a nearby waterfall, the beautiful Salto de Jimenoa. I was surprised to find several educational signs about the forest posted along the trail, covering topics including land use history, geology, and, most importantly, flora and fauna. Nestled in a paragraph about reptiles and amphibians, it noted the following (in Spanish, English, French, and German, no less!): “The amphibians are represented by lizards and frogs… A good observer can see lizards of the Anolis species jumping from the trees or walking on the ground and birds can be appreciated.” While some of the biology might not have translated very well, it was good to see anoles getting the shout-out they deserve!
These anoles were featured on interpretive signage in the Dominican Republic.
This post serves as a lighthearted response to Jonathan’s earlier announcement and as an advertisement – perhaps endorsement – for some of the upcoming anole talks at Evolution 2012.
In his post Jonathan highlights recent comments by David Hembry that describe the blossoming of anoles into “field model organisms,” the ecological parallel of chicks, mice, and Drosophila which have long histories in laboratory studies. While the importance of anoles for Evolutionary Ecology is almost without question, I think that this stops short of describing the present and undeniable future of anole research. From my perspective, the roots of Anolis research are strong and wide, but its flower(s) has not yet fully blossomed.
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?