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.

Oceanic Dispersal by Tortoises and Iguanas

tortoise

tortoise routeRecently, a 2006 paper on giant land tortoise dispersal has been going around social media. The story is that a tortoise from Aldabra, a tiny speck of an island north of Madagascar, washed ashore in Tanzania, some 700+ kilometers away. Barnacles encrusted on the tortoise’s legs suggest that the chelonian had been adrift for 6-7 weeks, an estimate that makes sense given the prevailing currents. The article summarizes several other, not-quite-so-well documented, cases of tortoise dispersal. These stories make clear that tortoises can disperse over long distances of open ocean. Thus, it is not surprising that they occupy far-flung islands around the world (and remember that until the onslaught of humans, they used to occupy many more islands, such as Madagascar, Mauritius, and New Caledonia).

This is all well and good, but why discuss it in Anole Annals? After all, our little four-legged friends weigh a few grams, not many kilograms, and they don’t carry a flotation device on their back. Does the dispersal ability of these behemoths tell us anything about how anoles reached their island homes?

Let’s go to an example closer to home, from a paper in 1998 published by Ellen Censky in Nature. In that paper, Censky et al. reported an observation from 1995 of a large mat of vegetation washing ashore on the Caribbean island of Anguilla (described as “a mat of logs and uprooted trees, some of which were more than 30 feet long and had large root masses. Local fishermen say the mat was extensive and took two days to pile up on shore.”). This in itself was not so unusual—such mats wash ashore regularly, especially in hurricane season. What was unusual is that riding this vegetation was a passel of green iguanas, a species native to some islands in the Caribbean, but not Anguilla. As onlookers watched, the vegetation washed ashore and, like tourists disembarking from a cruise ship, the 15 iguanas stepped off onto the beach. And like the occasional tourist, the iguanas liked it so much that they never left. Rather, they settled, put down roots, and raised a family. As far as I know, the iguanas are still there to this day.

censkyBut where did they come from? One bit of information did not make it into the article, but Ellen Censky has kindly allowed me to report it here. There was a clue in the mat of vegetation, in the form of a street sign. In French! That narrowed the possibilities considerably, and a bit of sleuthing established that the street sign, and hence the saurians, came from the island of Guadeloupe, where iguanas are native, and where Hurricanes Luis and Marilyn had struck some weeks before. Hurricanes often knock enormous amounts of vegetation into the water, explaining the formation of the vegetation mat.

True, iguanas are bigger than anoles, but otherwise this is exactly the mode of transport hypothesized for anoles. For example, large amounts of vegetation often fall into the Amazon and Orinoco Rivers in South America and end up floating far out to sea, as chronicled by Blair Hedges in a paper a while back. It’s not that hard to imagine a female, with eggs or storing sperm, hunkered down in such vegetation and managing to survive such a journey. It probably doesn’t happen often, but as Ernest Williams pointed out in an overlooked paper on colonization years ago, given millions of years, the unlikely becomes probable. Phylogenetic evidence indicates that the Caribbean anole radiations are the result of two colonization events from the mainland. In addition, it suggests that the Norops radiation on the mainland is a result of back-colonization from the islands—over the 40 million plus year history of anoles, that doesn’t seem very unlikely.

Island Gigantism in a Mexican Anole

Anolis nebulosus

In a recent paper in the Italian Journal of Zoology, Senczuk and colleagues report an interesting finding on the clouded anole, Anolis nebulosus. On the mainland, the species is fairly petite, with males averaging 40 mm SVL. However, on a very small, offshore islet, only half a kilometer from the mainland, males grow to an average of 53 mm, and the average female is larger than the largest male on the mainland.

What is responsible for such great disparity in size? Two prime possibilities are that most of the anoles predators are absent from this small island and that the island has a seabird colony, which may lead to greater quantities of insect prey.

In a fascinating previous study, some of the authors of this paper documented many other interesting differences between the mainland and island populations, such as the fact that lizards in the island population are much more active and display more. Clearly, this is a situation worthy of further study.

Abstract:

The clouded anole Anolis nebulosus (Squamata: Polychrotidae) is widespread on the Pacific coast of Mexico. The species also inhabits Don Panchito, a small islet located near the coast of the Chamela-Cuixmala Biosphere Reserve in the state of Jalisco. We studied the extent of intraspecific differences in morphology (absolute size and body proportions) and in mtDNA sequences (16S and NDH2) between the population living on the islet (N = 18 for morphometry; N = 12 for mtDNA) and the one on the facing mainland (N = 38 for morphometry; N = 16 for mtDNA). The individuals on the islet are larger than those on the mainland with little overlap in size for either males (islet: 52.79 ± 1.82 mm; mainland: 40.96 ± 2.99 mm) or females (islet: 46.18 ± 3.24 mm; mainland 37.14 ± 2.13 mm). The presence of insular gigantism, as here found in A. nebulosus, seems uncommon in the genus and could be explained as a combination of low predation pressure and higher intraspecific competition on the island. Moreover, we found that sexual dimorphism (SD) is higher in the island population than in the mainland one. The molecular analysis shows the absence of shared haplotypes between the island and mainland populations. Ten mtDNA haplotypes belonged to the mainland population and three to the island population. The shape of the minimum spanning network and of the mismatch distribution indicates a single colonization event. These molecular data indicate a certain degree of isolation of the island population notwithstanding its proximity to the coast. The morphological characteristics of the anoles on Don Panchito match with the expectation of the so-called “reversed island syndrome” theory, which predicts an increased body size and sexual dimorphism in lizards living on very small islands characterized by unpredictable environmental conditions.

Aquatic Anole Displaying

Here at AA, we seem to have an obsession, hopefully healthy, for a few things: knight anoles, anoles and water, and big dewlaps. And here’s a combination of two of them, a mainland aquatic anole displaying its enormous dewlap. Wowwee! It’s big and beautiful. What is it with mainland anoles and their big throat fans? This is a youtube video posted by MrKbosker, identified as A. aquaticus.

And not to be outdone, InBio, the Costa Rican biodiversity institute, brings us this mellifluous footage of A. polylepis strutting its stuff.

The Anoles of La Cumbre, Colombia

ventrimaculatus DSC_0021x

Anolis ventrimaculatus. Photo by Jonathan Losos.

We (Rosario Castaneda, Anthony Herrel, Luke Mahler and I) have just completed the first leg of our 2.5 week Colombian anole sojourn. First up: La Cumbre in the hills north of Cali. At  2000 meters, it was chilly! Going out our first night, we found plenty of long-legged Anolis ventrimaculatus. Imagine our surprise the next day when they were hard to find when active! This was reminiscent to us of A. gemmosus in Mindo, which also is very abundant at night–we’re talking Caribbean anole night abundance–but not easy to find while active.

The ones we did find were generally low to the ground, often on tree trunks, sometimes on vegetation. They refused to move when we filmed them, but their stomach contents indicated that they had been foraging, even at temperatures in the upper teens. These are tough, wily buggers!

We found two other species in smaller numbers, but only at night. The most exciting was A. calimae, which was not known from the locality at which we were working. We found a male and a female. They look moderately like twig anoles–elongate, slender body habitus–but there limbs are on the long side. We’ll see what the morphometrics say. However, when we released them, they behaved exactly like twig anoles, squirreling to the far side of a branch, creeping forward, carefully placing one foot, then the next, freezing. Unfortunately, despite intensive efforts, none were located during the day, perhaps not surprising, as many twig anoles are very cryptic and hard to find, particularly given that they live in dense vegetation.

Female Anolis calimae. Photo by Jonathan Losos.

Female Anolis calimae. Photo by Jonathan Losos.

Lastly, we found a number of A. mariarum in dense fields of high, stout grass. The photo below shows one such area. These lizards have to be living in the grass; they’re too far from anything else (the occasional tree notwithstanding. Yet search as we might, we couldn’t find them during the day. Our guess is that they are active in the spaces on the ground beneath the grass. In fact, when we let the lizards go, they seemed quiet happy to scamper about, and even display at each other, under the grass canopy.

DSC_0029x

Anolis mariarum’s field of dreams, where several were found sleeping, but none could be found during the day.

An exciting, if chilly start, but we’ll soon be thinking wistfully of cool days and evenings as we head to our hot and steamy next location.

Anolis cristatellus Expands its Range in Costa Rica

 

Distribution records for Anolis cristatellus in Costa Rica reported in 2011 AA post.

Four years ago, we reported on the distribution of the Puerto Rican crested anole all along the Caribbean coast of Costa Rica. We also found the species inland, as far west as Turrialba and Siquerres, but not Guapiles (see map to right). A year later, we returned for a quick follow-up as part of a herpetology course spring break trip to Costa Rica. The weather wasn’t great and we failed to find cresteds in any place not previously reported; however, observations of brown basilisks, another sun-loving species, suggested that the weather was suitable enough, and that perhaps the absence of the anoles was real.

Two years later, this past March, another herpetology class trip ensued, and so another expedition was launched to Guapiles and environs. The team included AA correspondent Katie Boronow, an award-winning senior with expertise on A. cristatellus, and a sophomore in training for Miami field work this summer (more on them in posts to come).

And the results???

Continue reading

Anole Field Research Blogs

Great photos on Adventures Down South

Where do anoles poop? Will they chase laser points? Find out on Casey Gilman’s new blog on her Florida field research, Adventures Down South.  Meanwhile, Chipojolab keeps the world abreast of goings-on in the Leal Lab. Most recently–Leal back in the Bahamas and multiple lab members cavorting in Puerto Rico! And Ambika Kamath’s afoot with her field crew in Gainesville, dodging frisbees and fire ants in quest of the wily festive anole. Finally, at Lizard and Friends, Michele Johnson talks about Puerto Rican anoles that are biting off more than they can chew. Or are they?

Do you have a blog on your research? If so, let us know!

Field laboratory in Puerto Rico. Read all about it in Chipojolab.

More Research on Female Back Pattern Polymorphisms

Variation in the back patterns of Anolis sagrei in the Bahamas. From Calsbeek and Cox (2010).

The confusing conundrum of the polymorphic females continues. We’ve written about this phenomenon in previous posts [e.g., 1,2]. Within and between populations, female back patterns vary, including lines, stripes, diamonds, blotches, and nothing at all. What is the significance of this variation? In some cases, but not others, females with different patterns use different microhabitats–higher, wider, etc.

The latest contribution features work on the Bahamian island of Eleuthera, where three patterns co-occur. Writing in Herpetologica, Les et al. add a new twist–back pattern variants differ in hindlimb length. But they don’t differ in sprint speed (which is weakly correlated to body size and relative limb length) or to perch diamter. But they do differ in perch height. Another brick in the wall of female pattern polymorphism, but it doesn’t make the picture any clearer.

Here’s the abstract:

The Brown Anole (Anolis sagrei) is a polymorphic species, with females often exhibiting one of three distinct pattern morphs. Efforts to correlate female-limited pattern polymorphism in anoles to ecological or physiological factors have largely been unsuccessful, with such correlations being either inconsistent among species or among populations of a single species. To test the hypothesis that morph types would differ in their response to putative predators, we observed escape behavior in 84 female A. sagrei from Cape Eleuthera (Eleuthera, Bahamas) and tested 103 females for sprint speed. We found differences between morph types in hindlimb span and perch height. Differences in sprint speed were not significant, nor did morphs differ in escape responses. We suggest further studies to determine whether differences between morphs in hindlimb span are genetic or plastic, and, if plastic, what factor might be responsible. We conclude that perching at different heights could be selectively advantageous for different morph types, and that differences among individuals in sprint speed are largely consequences of hindlimb length. Because morphs in this population did not differ in escape responses, we suggest that different dorsal patterns are not linked to specific behaviors that could reduce detection by a potential predator.

 

Everything You Ever Wanted to Know about the Beautiful Anolis smaragdinus

smarag

The Catalogue of American Amphibians and Reptiles, produced by the Society for the Study of Amphibians and Reptiles, are “Loose-leaf accounts of taxa (measuring 8.5 x 11 inches) prepared by specialists, including synonymy, definition, description, distribution map, and comprehensive list of literature for each taxon. Covers amphibians and Reptiles of the entire Western Hemisphere. Individual accounts are not sold separately, except where indicated.”

CAAR entries are now freely available online; there are 32 anole species accounts. The latest is by Les and Powell and is a very nice CAAR entry for the lovely Anolis smaragdinus.

Anoles Make Guest Appearance on John Oliver Show

photo

Admittedly, they were in a piece on space geckos, but you gotta’ take fame where you can get it. Catch the clip here before Youtube takes it down.

And note that this is not the first time anoles have been mistaken for geckos by journalists. Let’s not forget the segment on the Sunday Morning CBS show, a misstep for which AA  led the blogosphere in breaking the news and eventually received a mea culpa from CBS.

New Special Issue on Morphology and Evolution of Lizards

anatomical record cover

Juan Daza asks: Can you identify this lizard?

He continues:

If you have no idea, it’s not because it’s not an Anolis; in fact, this is an imaginary lizard that was reconstructed based on the remains of a 110 my old fossil from the Gobi Desert and a mosaic of features from different living geckos such as Agamura persica, Pachydactylus rangeiTeratoscincus przewalskii, Hemidactylus turcicus, and Coleonyx variegatus (and check the dromeosaurids roosting at twilight).  This digital illustration drawn by Stephanie Abramowicz is the cover of a March Special Issue from the Anatomical Record: New Advances In Morphology and Evolution of Living and Extinct Squamates [freely available at: http://onlinelibrary.wiley.com/doi/10.1002/ar.v297.3/issuetoc].

The idea of a volume like this started with James D. Gardner and Randall L. Nydam. They wanted to put a collection of papers from the Paleo-session of the past World Congress in Vancouver. Instead, they ended up editing another multi-authored volume entitled: Mesozoic and Cenozoic lissamphibian and squamate assemblages of Laurasia (Palaeobiodiversity and Palaeoenvironments, 93(4), Special Issue).

This volume took a different approach, and we (Scott Miller and I) put together herpetologists and paleontologists from around the world in a volume to present new ideas about morphology and evolution of squamates. This volume is a collection of 18 papers about paleontology, functional morphology, and gross anatomy of lizards and snakes, and includes recent findings from researches from 12 countries (USA, Canada, Colombia, Brazil, Argentina, Spain, France, Italy, Germany, Slovakia, South Africa, and New Zealand).

So please feel free to browse this volume that includes original research papers about the fossil record of lizards and snakes, anatomy of the chameleon’s atlantoaxial complex, pedal grasping capabilities, and pectoral girdle anatomy of anoles, fossil record of the Gekkota, cranial joints of squamates, hemipeneal morphology, brille formation, cranial joints, ancestral morphology and niche modeling of rhineurids, Anguimorpha, and the jaw musculature, and gut morphology of snakes. I hope you find this stimulating and pick morphology today, for a change.

Table of Contents:

The Anatomical Record is Alive With Leapin’ Lizards and Slitherin’ Snakes (pages 337–340)
Kurt H. Albertine and Scott C. Miller

What’s So Special About Squamates? (pages 341–343)
Juan D. Daza and Scott C. Miller

Not Enough Skeletons in the Closet: Collections-Based Anatomical Research in an Age of Conservation Conscience (pages 344–348)
Christopher J. Bell and Jim I. Mead

An Overview of the South American Fossil Squamates (pages 349–368)
Adriana María Albino and Santiago Brizuela

The Atlas-Axis Complex in Chamaeleonids (Squamata: Chamaeleonidae), with Description of a New Anatomical Structure of the Skull (pages 369–396)
Andrej Čerňanský, Renaud Boistel, Vincent Fernandez, Paul Tafforeau, Le Noir Nicolas and Anthony Herrel

Anatomy of the Crus and Pes of Neotropical Iguanian Lizards in Relation to Habitat use and Digitally Based Grasping Capabilities (pages 397–409)
Virginia Abdala, María José Tulli, Anthony P. Russell, George L. Powell and Félix B. Cruz

Geometric Morphometric Analysis of the Breast-Shoulder Apparatus of Lizards: A Test Case Using Jamaican Anoles (Squamata: Dactyloidae) (pages 410–432)
Alexander Tinius and Anthony Patrick Russell

On the Fossil Record of the Gekkota (pages 433–462)
Juan D. Daza, Aaron M. Bauer and Eric D. Snively

To Move or Not to Move: Cranial Joints in European Gekkotans and Lacertids, an Osteological and Histological Perspective (pages 463–472)
Marcello Mezzasalma, Nicola Maio and Fabio Maria Guarino

Relict Endemism of Extant Rhineuridae (Amphisbaenia): Testing for Phylogenetic Niche Conservatism in the Fossil Record (pages 473–481)
Christy A. Hipsley and Johannes Müller

Are Hemipenial Spines Related to Limb Reduction? A Spiny Discussion Focused on Gymnophthalmid Lizards (Squamata: Gymnophthalmidae) (pages 482–495)
Pedro M. Sales Nunes, Felipe F. Curcio, Juliana G. Roscito and Miguel T. Rodrigues

Through the Looking Glass: The Spectacle in Gymnophthalmid Lizards (pages 496–504)Ricardo Arturo Guerra-Fuentes, Juliana G. Roscito, Pedro M. Sales Nunes, Priscilla Rachel Oliveira-Bastos, Marta Maria Antoniazzi, Jared Carlos and Miguel Trefaut Rodrigues

A New Miniaturized Lizard From the Late Eocene of France and Spain (pages 505–515)
Arnau Bolet and Marc Augé

Comparative Anatomy of the Lower Jaw and Dentition of Pseudopus apodus and the Interrelationships of Species of Subfamily Anguinae (Anguimorpha, Anguidae) (pages 516–544)
Jozef Klembara, Miroslav Hain and Karolína Dobiašová

Unusual Soft-Tissue Preservation of a Crocodile Lizard (Squamata, Shinisauria) From the Green River Formation (Eocene) and Shinisaur Relationships (pages 545–559)
Jack L. Conrad, Jason J. Head and Matthew T. Carrano

Postnatal Development of the Skull of Dinilysia patagonica (Squamata-Stem Serpentes) (pages 560–573)
Agustín Scanferla and Bhart-Anjan S. Bhullar
Article

Homology of the Jaw Muscles in Lizards and Snakes—A Solution from a Comparative Gnathostome Approach (pages 574–585)
Peter Johnston

A Model of the Anterior Esophagus in Snakes, with Functional and Developmental Implications (pages 586–598)
David Cundall, Cassandra Tuttman and Matthew Close

No Need for Sunscreen: Some Lizards Adjust UVB Exposure Depending on Vitamin D Intake

Gratuitous plug for a brand of sunscreen featuring a lizard.

Lizards not only sit in the sun to thermoregulate, but also to synthesize Vitamin D. It tends to reason, then, that the amount of basking might depend on the amount of Vitamin D in the diet. And so it does, at least in A. sagrei. But, not in the more shade-loving A. lineatopus. Read all about it in Gary Ferguson’s paper that appeared in the Journal of Herpetology at the end of last year.

Abstract:

In Jamaica, free-living male and female-sized Anolis sagrei are exposed to more natural ultraviolet-B (UVB) from sunlight than male and female-sized Anolis lineatopus. In the laboratory, we tested predictions derived from the hypothesis that Anolis possess a mechanism for behaviorally photo-regulating their exposure to UVB depending on their dietary intake of vitamin D3. Anolis sagrei voluntarily exposed themselves more frequently to visible and UVB light and received higher doses of UVB in an artificial light gradient when fed a low vitamin D3 diet for 6 weeks than when subsequently fed a high dietary vitamin D3 diet for 6 weeks. When we returned the anole’s diet to the low vitamin D3 regimen for a third 6-week period, UVB exposure remained lower than in the first 6-week period. This suggests an initial UV photoregulatory adjustment to high dietary vitamin-D3 but a slow return to greater reliance on UVB-induced endogenous vitamin D3 production. Conversely, while exposing themselves to UVB with similar frequency and doses as A. sagrei over the course of the 18-week experiment, A. lineatopus did not show the same decreased attraction to visible and UVB light in response to increased dietary vitamin D3. The response of A. sagrei in the laboratory to visible light without UVB was similar to their response to visible light with UVB. Therefore, the anoles appeared to be responding primarily to visible light. Anolis lineatopus may be unable to use dietary vitamin D3 to restore low vitamin D status.

 

HHMI Unveils Lizard Classroom Exercises to Teach Evolutionary Concepts

hhmi

The Howard Hughes Medical Institute earlier this year introduced a short film on anoles for use in teaching principles of evolution to high school and science biology classes. Now they’ve come up with a fabulous set of online class exercises to be used in conjunction with the film, the Lizard Evolution Virtual Lab!

I have to say, the exercises are fantastic! The exercises, which include data collection and analysis, include how to study phylogeny, natural selection and adaptation. Here’s how they describe it:

The virtual lab includes four modules that investigate different concepts in evolutionary biology, including adaptation, convergent evolution, phylogenetic analysis, reproductive isolation, and speciation. Each module involves data collection, calculations, analysis and answering questions. The “Educators” tab includes lists of key concepts and learning objectives and detailed suggestions for incorporating the lab in your instruction.

It is appropriate for students in high school biology and environmental science classes, and undergraduate biology, ecology, environmental science courses. The focus on observation, measurement, and experimental methods makes the lab a good fit for addressing “science as a process” or “nature of science” aspects of the curriculum. The emphasis on the collection, analysis, and graphing of data, connects to the mathematical dimension of biology and general goals of STEM integration.


Key Concepts:

  • An adaptation is a structure or function that confers greater ability to survive and reproduce in a particular environment. (Modules 1 and 3)
  • DNA sequence comparisons among different populations and species allow scientists to determine how distantly related different species are and how long ago they split from a common ancestor. (Module 2)
  • Different species can independently evolve similar traits by adapting to similar environments or ecological niches in a phenomenon known as convergent evolution. (Module 2)
  • The biological definition of a species is a group of interbreeding individuals that are reproductively, and thus genetically, isolated from other groups. (Module 4)
  • When two groups within one species become geographically isolated—separated by a physical barrier, such as a river, canyon, or mountain range—genetic changes in one group will not be shared with members of the other, and vice versa. Over many generations, the two groups diverge as their traits change in different ways. (Modules 3 and 4)
  • For two groups to become distinct species, traits must change in ways that will keep members of each group reproductively isolated—meaning that they will not mate or produce fertile offspring with members of the other group—even if they come to be in the same geographic location. (Module 4)
  • Graphing data is an important way to objectively document differences and similarities. It can make it easier to spot patterns that would otherwise be difficult to see in tables of measurements or direct observations. (Modules 1, 3, and 4)
  • Statistical tools provide a way to quantify variability in biological data and describe the degree of uncertainty in the results obtained using these data. (Modules 3 and 4)