Category: New Research Page 48 of 67

Wrapping up our coverage of the World Congress of Herpetology held in Vancouver last week, I have a report on Nick Crawford’s talk on the genetics of colorful pigmentation in Anolis.  Nick began by talking about the basic types of pigments that contribute to anole coloration, which include both pteridines and carotenoids.  Synthesis of pteridines is much better understood, thanks largely to work on zebra fish (reviewed in Braasch et al. 2007).  Nick first showed preliminary evidence from rtPCR analyses suggesting that specific genes along the pteridine synthesis pathway differ in predictable ways among parts of anoles with different coloration (e.g., white venter, green dorsum, pink dewlap).

Crawford went on to note that pteridines may be less important to dewlap coloration than are carotenoids, but that the latter represent a bit of a black box genetically and developmentally.  Crawford then discussed a project in which he uses a bulk segregant approach to ask if regions of the genome associated with color differentiation can be identified by examining genomic sequence data from species with polymorphic coloration.  Crawford was particularly interested in the polymorphic Lesser Antillean Anolis marmoratus.  He obtained sequence data from two phenotypically distinct populations of this species using the Illumina hiSeq platform.  Fortunately this data could be aligned to the A. carolinensis genome, and showed a relatively high degree of synteny with this previously published genome.  Analyses of the new A. marmoratus dataset are still in their early stages, but preliminary analyses recover 1,300 fixed SNPs (only 330 of which appear to be exonic) and suggest the presence of genomic islands of differentiation similar to those reported in many other recently diverged species and incipient species.

Note Added in Press:

One talk we failed to cover at WCH was by Chris Schneider on a similar topic. Here’s the Abstract:

Schneider, Christopher (Boston University); Crawford, Nicholas; McGreevy, TJ; Messana, Nick (Boston University, Canada)

The genetic basis of phenotypic variation and divergence in Anolis marmoratus

In what should be our final belated post about talks at the Evolution meetings in Ottawa last month, I’d like to share some results from Bryan Falk from Susan Perkins’s Lab American Museum of Natural History.  Bryan has been investigating the diversity of anole malaria parasites (Plasmodium).  Like many other species of vertebrates, anoles have their own strains of malaria (not the same as the ones that effect us humans), and these lizard malaria have been the focus of numerous fascinating research projects over the years (see Schall 1996 for a review).

Bryan’s work investigated phylogenetic relationships among West Indian strains of lizard malaria using sequence data from mitochondrial DNA plus six nuclear loci.  He found that Plasmodium samples on most islands form monophyletic groups, although some clades are found in both Florida and Cuba, suggesting travel between these two regions.  Bryan also reported very low overall genetic diversity, the presence of most genetic variation among (rather than within) populations, and no evidence for purifying selection.  Bryan’s previous work used tree-based delimitation to diagnose previously unrecognized or ambiguous taxa of Plasmodium on Hispaniola, and his new work uses a similar approach across a broader geographic scale.  In the new study, species tree analyses tend to recover island-specific clades and identify 11 potentially unrecognized species within Plasmodium floridense (see Perkins 2000 for more on species delimitation in Plasmodium). Bryan’s time calibration work suggests that intra-island divergences are very young and his demographic analyses suggests that recent divergence and serial bottlenecks may be responsible for low diversity with in populations but high divergence among populations.  It seems like more exciting new results with anole malaria on are on the horizon from Bryan and his collaborators.

The New York Times covered the story, too. http://graphics8.nytimes.com/images/2012/08/08/blogs/cat/cat-blog480.jpg

We reported earlier this month on the talk at the Ecological Society of America where a University of Georgia researcher put kitty cams on housecats to see where they went and what they did. And one finding: they caught a lot of anoles! USA Today ran an article on the front page, and included a video online that has some grisly (ok, not that grisly) footage of this, as well as other cool stuff (encounters with other animals, secret lives of housecats). Check it out!

One of the brown anole males in the McMann and Paterson study. Photo by Stephen McMann.

Anole Annals readers know otherwise, but many people consider lizards to be simpletons, with nary a thought in their head. But that’s mistaken–it’s salamanders that are the truly stupid ones (sorry for the tangential ad hominem). Lizards have more going on upstairs than people realize. Sure, they’re not the sharpest knife in the drawer, but they’re no dummies, either.
Case in point: lizards are able to recognize and differentiate among other lizards. This conclusion, which has now been demonstrated a number of times, was reinforced by a recent paper by McMann and Paterson in Herpetological Conservation and Biology. They set out to test whether  brown anoles react differently when confronted with a neighbor than when confronted with a lizard that lives farther away and that, presumably, the lizard has not interacted with in the past. This is a test of the phenomenon termed “dear enemy,” the idea that neighbors get to know each other and come to a mutual coexistence in which, when they encounter each other, they go through perfunctory displays, but don’ t get all riled up, because they’ve already been through all of that before. The dear enemy phenomenon has been demonstrated previously in a variety of other lizards. Indeed, these authors have demonstrated it before with brown anoles, but that work was conducted in experimental arenas. This time, the authors wanted to see what happened when the research was conducted in nature, in animals’ own territories. To do this, they presented territorial males with another lizard enclosed within a small cage.

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We’re just wrapping up a few last posts from last week’s World Congress of Herpetology in Vancouver. In a tour de force, Laura Rubio-Rocha presented two posters, side-by-side, in the first night’s session. We’ve already discussed her doctoral work on geographic variation in adaptation to different climates in A. carolinensis; here I briefly mention her poster on a high elevation Colombian anole that exhibits year-round reproduction in an environment in which there are two rainy seasons. This interesting study was recently published; you can learn more about it in our previous post on that paper.

A sampling of the anoles examined by Emma Sherratt

The World Congress called on Emma Sherratt to serve as the closer, presenting the last talk on the last day of the meeting. The choice proved brilliant, as she sent the audience off to the banquet in high spirits with a captivating report on her examination of 30+ specimens of amber-encased anoles. Emma has already wowed us with  the images and videos she produces by micro-CT scanning; needless to say, the audience was amazed. Preliminary analyses suggest that multiple species are present in the sample (only one amber anole has been described in the scientific literature), and several of the types may match present-day ecomorphs. Her abstract:

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Travis Ingram reported on a new method he devised to test whether the anole radiations on the Greater Antilles are more similar than might be expected to occur by chance. We all know that each island has experienced its own radiation, producing more or less the same set of ecomorphs. However, some islands have more ecomorphs than others (Jamaica: 4; Cuba, Hispaniola: 6). In addition, there are non-ecomorph species on the larger islands. It is always possible that it is just a coincidence that the same types have evolved on multiple islands. After all, given large enough evolutionary radiations, one would expect the same morphology to evolve by chance on multiple islands. Travis developed a method to test this hypothesis, and found that, indeed, the Greater Antillean radiations are more similar in morphology than would be expected by random evolutionary change. Read all about it in the abstract:

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Sebastian Lotzkat presented a fascinating talk on geographic variation, both morphological and genetic, in Panamanian reptiles, emphasizing the highlands of western Panama. Although he discussed a wide range of species, he spent an appropriately large amount of time focusing on anoles, which if I recall correctly, he termed his favorites. To cut to the chase, he’s found very large amounts of variation in almost every species examined, including in some cases dividing species into several new species. Some of this work has already been chronicled in AA, and another paper will soon be reported on, but apparently there is a lot more yet to come. Read the abstract below the fold.

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Anole brains. For scale, the partial coin is an American penny.

A pair of talks from Duke University took different approaches to examining anole smarts. Recently minted Ph.D. Brian Powell reported on his examination of the brain size and composition of different anole species. Brian reasoned that anoles living in different habitats would evolve differences in brain structure corresponding to the different challenges they faced, and thus that species that use the same habitat should have converged on brain morphology. However, results failed to support this hypothesis and instead indicated that the size of different brain components evolves in concert. More details below.

The three species that have demonstrated behavioral flexibility in the lab. Sure wish I could remember what the third point was

Later in the meeting, Manuel Leal reported on the cognitive flexibility of several anole species. Previous work has shown that A. evermanni is not only adept at solving novel problems, but can reverse previously learned patterns so as to ignore the stimulus that previously was rewarded and instead respond to a stimulus that previously hadn’t been rewarded. Leal has now extended that work to show that two other anoles can do the same. He then went on to test how adept anoles are at telling apart two similar patterns. He found, surprisingly, that they could tell very different patterns apart, but did not seem to be able to distinguish more similar patterns. Leal concluded by wondering whether minor differences in signals are detectable by receivers, which is an underlying assumption of many studies of sexual selection and communication. Manuel’s abstract is below the fold as well, although he went off-script in much of the talk he presented.

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A male Anolis cristatellus dewlaps on a tree in Miami, Florida. Picture reproduced with permission from Kolbe et al. (2012).

Anoles are remarkably adaptable creatures. You can find anoles in hostile environments, such as the tops of mountains in the Dominican Republic, in near-desert environments, and in places with over-winter freezing. Anoles are also a model system for rapid evolution; in response to strong selective pressure, an equally strong evolutionary response occurs within a few generations. It is perhaps unsurprising, then, that anoles are also one of the most invasive reptiles in the World. Although they are endemic to the tropical and subtropical regions of the New World, today anoles can also be found in such remote places as Guam, Hawaii, Taiwan, and Hong Kong.

One of the major questions surrounding anole invasions is how the organisms will respond to the challenges of a new environment. When anoles invade new environments they inevitably encounter new thermal and hydric conditions – how do these anoles adapt to a different environment? Jason Kolbe has spent many years exploring the ecology and genetics of Anolis invasions, and has focused especially on invasions in Florida (1, 2, 3). The Puerto Rican trunk-ground, A. cristatellus, has been found in Key Biscayne and South Miami since the mid-1970s. Ambient temperature is important for A. cristatellus and other anoles have been documented to acclimate to low temperatures. In this study Jason Kolbe and colleagues addressed two questions: (1) To what extent does the thermal environment change from Puerto Rico to Florida? and (2) Is there a phenotypic response in tolerance to cold?

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