All posts by Jonathan Losos

About Jonathan Losos

Professor and Curator of Herpetology at the Museum of Comparative Zoology at Harvard University. 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.

Are There Seven Species of Anolis distichus?

distichus

The latest work on genetic differentiation and species status within the Anolis distichus group has just been published by MacGuigan, Geneva and Glor in Ecology and Evolution. In line with previous work from the Glor lab, the study finds evidence for seven distinct evolutionary lineages worthy of recognition as species, and further finds that variation in dewlap color in some cases does not correlate with geographic isolation. Finally, geographic isolation seems to play a key role in genetic divergence.

Here’s the abstract, followed by a few comments:

Abstract

Delimiting young species is one of the great challenges of systematic biology, particularly when the species in question exhibit little morphological divergence. Anolis distichus, a trunk anole with more than a dozen subspecies that are defined primarily by dewlap color, may actually represent several independent evolutionary lineages. To test this, we utilized amplified fragment length polymorphisms (AFLP) genome scans and genetic clustering analyses in conjunction with a coalescent-based species delimitation method. We examined a geographically widespread set of samples and two heavily sampled hybrid zones. We find that genetic divergence is associated with a major biogeographic barrier, the Hispaniolan paleo-island boundary, but not with dewlap color. Additionally, we find support for hypotheses regarding colonization of two Hispaniolan satellite islands and the Bahamas from mainland Hispaniola. Our results show that A. distichus is composed of seven distinct evolutionary lineages still experiencing a limited degree of gene flow. We suggest that A. distichus merits taxonomic revision, but that dewlap color cannot be relied upon as the primary diagnostic character.

The authors suggest that there are at least seven species within the distichus complex, but they suggest that it is premature to recognize them officially at this time. Nonetheless, Poe et al. in their recent Systematic Biology paper (hey! who’s going to write a post on this one?) recognize at least some of these taxa as distinct species.

Finally, I do have one tiny bone to pick. The authors state:

“Together these results suggest that dewlap color is not by itself a reliable diagnostic trait in the A. distichus complex, and perhaps in anoles more broadly.”

I take umbrage with the final statement, “and perhaps in anoles more broadly.” The distichus complex has always been recognized as the major exception to the idea that dewlap color variation relates to reproductive isolation. Consequently, demonstrating what has been suggested—with some evidence—for 40 years doesn’t necessarily argue against the role of the dewlap in reproductive isolation more generally. Now, you may quibble with the data underlying this general proposition, and it certainly is worthy of further study, but the results of this study confirm what was already recognized as an exception to this general rule..

 

Anolis ruibali: Everything You Need to Know

ruibali

The following is taken from the Society for the Study of Amphibian and Reptile’s website:

Catalogue of American Amphibians and Reptiles

The Catalogue consists of accounts of taxa prepared by specialists, including synonymy, description, diagnosis, phylogenetic relationships, published descriptions, illustrations, distribution map, and comprehensive list of literature for each taxon. Over 900 accounts have been published since the initiation of the series in 1963. The series covers amphibians and reptiles of the entire Western Hemisphere. Previously, accounts were published as loose-leaf separates; beginning in 2013 accounts are published as on-line PDFs.  All accounts are open access and are available for free download at the University of Texas Library Repository.

Just this week, one of the latest catalogue entries is for the little known Anolis ruibali of Cuba, written by Robert Powell, Javier Torres, and Nils Navarro Pacheco.

ruibali2

Teid Lizard Eats an Anole

Poor Anolis, snack box of the jungle. Seems that just about anything will eat an anole. So, it’s not surprise to learn that the teid lizard Kentropyx calcarata joins the lizard of anole consumers. So report Franzini et al. in a recent report in Herpetology Notes. Anolis fuscoauratus was the unfortunate victim, the crime discovered by examination of stomach contents.

How Do Limb, Head and Tail Length Differences Arise during Embryological Development in Lizards?

andrews2

Consider two lizard species that differ in limb length, with one species having relatively longer legs than others. During development, how does this difference arise? Do the limbs start at the same length when they first appear in the embryo, but grow at a greater rate in the longer-legged species? Or is the initial limb bud longer in the embryo of the longer-legged species, and then the rate of growth the same in the two species, preserving the initial difference?

Thom Sanger’s elegant work showed that the latter answer is correct for Anolis: the limb buds of long-legged species start out longer and then grow in parallel with those of shorter-legged species.

But does this finding also hold when comparing across a broader range of lizards? Robin Andrews and Sable Skewes decided to find out, comparing embryos of a chameleon, two geckos, and the brown anole.

The answer: the same pattern as within anoles! And it applies to tail length (but not head length) as well as limbs.

andrews

Evolutionary Predictability: Can We Predict the Color of One Lizard Species by Looking at Repeated Patterns of Geographic Variation on Other Islands?

Thanks to the work of Roger Thorpe and colleagues, Lesser Antillean anoles are renowned as an example of adaptive geographic variation. On many islands in the Lesser Antilles, populations in wet areas, where vegetation is lush, are green in color, whereas those in more xeric areas tend to be a drab gray, often with markings on their back. This pattern is repeated on many different islands, the convergent geographic variation thus making a strong case for the adaptive basis of anole coloration.

See Pavitra Muralidhar’s previous post for more information on geographic variation in Lesser Antillean anoles.

In a new paper in PLoS One, Thorpe takes this work a step further, asking whether we can use the parallel patterns seen across Lesser Antillean islands to predict the coloration of an anole species on another island. The focal species is Anolis bonairensis, which occupies the extraordinarily dry island of Bonaire (see our previous posts on this species).

The prediction: A. bonairensis should be grayer and drabber than populations of anoles that occur at the driest sites on Lesser Antillean answers.

The answer: yes! Just as predicted, Anolis bonairensis is one drab lizard. Score one for evolutionary predictability!

thorpe

Anolis bonairensis is represented by the red circles. The x-axis goes from aridity on the left to the most mesic on the right. As you can see, A. bonairensis‘s color and patterning is well-predicted by variation in other species.

New Mainland Green Anole Recognized

Anolis biporcatus, one of the prettiest of anoles. Photo by Thomas Marent

Anolis biporcatus is, if I’m not mistaken, the largest mainland beta/Norops anoles, attaining a length of ca. 100 mm snout-vent. In addition, it has an enormous geographic distribution, ranging from southern Mexico to Ecuador. In a new paper in Salamandra, a team of New Mexican and Ecuadorian biologists headed by Janet Armstead have sliced off part of the species, raising the Ecuadorian/Colombian A. biporcatus parvauritus to species status. They make this decision based on a detailed analysis of morphology and molecular data. Their data also find deep genetic subdivisions within A. biporcatus in Costa Rica, suggesting that there may be more cryptic species awaiting recognition.

A key difference between the species is the color of the distal scales on the dewlap of males, white in biporcatus, black in parvauritus.

biporc male

Note, too, that like many mainland anoles, the males and females have very different dewlaps.

biporc females

Here’s the distribution of the two species:

map

More On Blue-Eyed Anoles

Anolis etheridgei. Photo by Rick Stanley.

Anolis etheridgei. Photo by Rick Stanley.

Three-and-a-half years ago, I wrote a post on the phylogenetic distribution of blue eyes in anoles. They pop up all over anole phylogeny and in species with diverse habitats and geography. The post attracted 32 comments.

At the time, I asked if anyone had a photo of the blue-eyed Anolis etheridgei. Photographer par excellence Rick Stanley quick obliged, but I never got around to posting his photo, so here it is.

But the bigger question is: what about those blue eyes? Why hasn’t anyone studied the phenomenon? If you’ve got a good photo of a blue-eyed anole, send it here!

Green Anole Displays to Wren

Photo by Barb Karl

Photo by Barb Karl

Everyone who has studied anoles in the field has had the experience of an anole displaying towards him- or herself. Do anoles actually display to real predators in the field? We’ve even had one AA post reporting a test of that. But there are few observations of such displays. So we were delighted to receive the following note from Barb Karl of Leland, North Carolina:

I was mowing my lawn and was startled by a green lizard that jumped to a nearby tree. I researched what type of lizard it was since we just moved to North Carolina a short while ago and wanted to see what it was.  I found that it was an anole.  I felt bad that I had startled him, so put some live mealworms on the fence as a peace offering.  I checked a little bit later and he was back on the fence, hopefully eating the mealworms.  Then a short distance away a wren appeared in the bird feeder tray.  I watched the anole, he was still on the fence and started going up and down (almost like he was doing pushups and his throat pouch would go in and out). It was like he was trying to make himself bigger so the bird would not want to mess with him.  It was an awesome sight!

I spotted a second Anole on a tree a distance away from the first one.  Can’t wait till they visit again.  Next time I will try and catch a video if it happens again.

The Extended Evolutionary Thesis and Anoles: the Evolution of Phenotypic Plasticity

Tobias Uller at Lund University is studying phenotypic plasticity in anoles to address the evolutionary significance of such plasticity. He’s interviewed at David Sloan Wilson’s siteThis View of Life. The whole interview is interesting, but here’s the snippet on anoles:

One of my projects, with evolutionary developmental biologist Nathalie Feiner, will test if plasticity shaped diversification of Anolis lizards. These lizards are textbook examples of an adaptive radiation because, across the Caribbean, a single species gave rise to multiple species, each locally adapted to a different habitat. We are particularly interested in limb morphology since it is a defining feature of adaptive differences between species; lizards that run around on broad surfaces, such as tree trunks, have longer limbs than those who cling onto twigs, for example.

Anolis equestris. Image used with permission of Tobias Uller.

We already know from work by Jonathan Losos and others that limb growth is plastic in Anolis. What we do not know is if evolutionary diversification of limbs took place through modification of those particular components of bones that respond to mechanical stress during growth – as would be predicted if plasticity ‘took the lead’ in evolution – or if adaptive divergence between species is unrelated to plastic responses within species. To test the concordance between plasticity and evolutionary diversity we rear a lot of lizards from several species on different surfaces and combine this with detailed measures of skeletons of very many species across the entire Anolis group.

We should also remember that plastic responses in some cases can carry over to the next generation. In experiments on water fleas, which have the advantage that they can reproduce clonally so we can rear genetically identical individuals in the lab, we will test the hypothesis that such maternal effects (or non-genetic inheritance) facilitate adaptation to new environments. In some ways, this works just like plasticity within a generation. That is, successful accommodation of environmental stressors enables populations to persist and gives natural selection something useful to work with, thereby providing directionality to evolution.

But here there is another twist that has to do with the evolution of inheritance. As populations adapt, selective removal of costs and negative side-effects should make maternal effects behave like signals, sent from mothers to tell offspring about the environment they are likely to encounter. This process, therefore, describes the evolution of a type of inheritance system.

We cannot study the conversion of an environmentally induced stress response to a detection-based inheritance system in the lab. But we can compare water flea populations that have been exposed to the same stressor, such as metals or toxins, for a different number of generations in the wild. Ultimately, this should give insights into how inheritance systems evolve and how they come to transmit information.

Experimental Study Demonstrates Anolis humilis Avoids Aposematic Prey

humilis paper

Aposematic warning patterns are supposed to have evolved to warn potential predators to stay away. But do they work? An experimental study at the La Selva Biological Station in Costa tested that hypothesis on common ground anoles, Anolis humilis. Baruch et al., writing in the Journal of Herpetology, presented the anoles with clay models painted in an aposematic or cryptic color. The models were dangled in front of the lizards and wiggled around, simulating a flying insect. Sure enough, the lizards went after the cryptic models nearly half the time, but almost completely ignored the orange and black ones. Aposematic patterns work!

The Horned “Rhino Lizard” of Sri Lanka

ceratophora

Here at AA, we love lizards with horns on the tip of their snouts. The horned anole, Anolis proboscis, is of course our favorite, but there are others. For example, Sri Lanka is home to the little known Ceratophora stoddardiAnima Mundi, an online magazine produced by an Italian husband-and-wife team, just had a nice seven page spread on this species, which it dubs the “rhino lizard,” replete with beautiful photos and a bit of natural history information. Like the horned anole, the rhino lizard can move its horn! I wonder what would happen if they ever met. Who knows? But if you want to learn more about the rhino lizard, check out our previous post on the species.

Cover Photos Needed for New Book on Honduran Reptiles

Two years ago, the Museum of Comparative Zoology published Randy McCranie’s book on the anoles of Honduras. Now, the MCZ is soon to publish Randy’s latest work, a massive compilation on the lizards, crocs and turtles of Honduras, to be titled, appropriately enough, The Lizards, Crocodiles, and Turtles of Honduras: Systematics, Distribution, and Conservation. 

How would you like your photograph to grace the front or back of this forthcoming volume? We’re looking for beautiful photos of Honduran lizards, crocs or turtles. The front cover photo must be vertical in aspect, the back cover horizontal. We can’t offer to pay you, but we’d be happy to provide you with a copy of the volume when it appears.

Please send photos to anoleannals@gmail.com

Thanks!

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Back cover of Anoles of Honduras