Category: New Research Page 56 of 66

From Falk et al., 2011.

The Gates Foundation today announced a multi-billion dollar initiative to eradicate malaria from all lizardkind. Through a combination of heightened prophylactic use, development of genetically modified lacertilians, and enhanced mosquitivory, the Foundation hopes to eliminate this scourge, which afflicts millions of saurians throughout the world.

Well, maybe some day. But a recent paper on Anolis malaria set my mind a-wandering. Most people, likely the Gates Foundation included, are unaware that malaria is a disease not just of humans, but of many other species as well, including lizards. When I first learned that lizards got malaria, I thought it was just a curiosity, not of particular importance. However, I’ve come to realize that I was very wrong in a number of respects.

First, malaria in some cases can have substantial physiological effects on lizards (though this has yet to be demonstrated in anoles).

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Everyone knows the devastating effect that the chytrid fungus (Batrachochytrium dendrobatidis) has had on amphibian populations almost everywhere in the world–in 2009, it was estimated to infect at least 350 amphibian species on 6 continents.

A sad photograph of frogs killed by the chytrid fungus (image from the UC Riverside Center for Invasive Species Research website)

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Anolis equestris with a radio transmitter attached. Photo courtesy Paul Richards.

Knight anoles, Anolis equestris, are truly the king of anoles. The largest anole species*–with a total length approaching two feet–and a grotesquely handsome and imposing head, these lizards are surely the reigning emperor of anoles.

Little, however, is known about the natural history of these species, other than they will eat anything they can get their jaws on. Introduced into Florida many years ago, Miami populations of knight anoles would seem to be ripe for study, but little work has been published.

Nicholson and Richards have taken a step in filling this void, reporting the results of a year-long radio-tracking study conducted on the grounds of the University of Miami. The authors developed a backpack mounted radio transmitter that they strapped onto the back of knight anoles, and then located them over the course of many months. The units were small (6 g or less) and didn’t seem to hinder the lizards, which were seen mating and engaging in other activities while backpack-clad.

The primary focus of the paper is home range of these lizards, and they report several results. First, knight anoles have a large home range, on average, of about 650 square meters. This result is not surprising, as home range size seems to be strongly correlated with body size among the 15 anole species for which data are available, and the two other large anoles have comparably large ranges.

More surprising is that there is little difference in the size of home ranges of males and females, unlike what is seen in many other anole species, in which male home range is larger, often substantially. Nicholson and Richards attribute this to the arboreality of this species, although other arboreal species, albeit smaller, have also been studied with variable results. I wonder, too, whether gender differences in home range size might correlate with degree of sexual size dimorphism. Certainly, several of the species with low dimorphism had female ranges larger than those of males.

The authors also found substantial overlap in territories of individuals, both within and between sexes, an intriguing finding that suggests that detailed studies of behavior of this species–of which almost nothing is known–would be very interesting. More generally, the biology of the knight anole is mostly a blank slate. These lizards are reasonably common in Miami, and there is great work to be done. Particularly interesting would be the community effects of this species–how does its presence affect the other anole species with which it occurs?

*The largest anole species is actually a matter of dispute, as it may be one of the knight anole’s sibling species, such as A. luteogularis. In all, the equestris species complex is comprised of six species, five of which are very large.

Knight anoles can bite hard and Kirsten Nicholson values her hands. This is how the transmitter’s are placed on the lizard. Photo courtesy Paul Richards.

Kirsten E. Nicholson and Paul M. Richards (2011). Home-range size and overlap within an introduced
population of the Cuban Knight Anole, Anolis
equestris (Squamata: Iguanidae) Phyllomedusa, 10 (1), 65-73

The International Congress on Vertebrate Morphology will be convening in Barcelona, Spain July 8–12, 2013. I have found past meetings extremely enjoyable with many exciting talks. How many from the anole community are considering attending?

The call for symposia for ICVM 10 was recently announced and the deadline for proposed symposia is April 15. With the growing number of labs studying anole development is it time to consider organizing an anole evo-devo symposium? What about a “reptilian” evo-devo symposium that brings together biologists working on other squamate, crocodilian, and turtle species? Perhaps its too soon or maybe another meeting? While mulling these ideas over I would appreciate hearing thoughts from others in the community. Please leave your comments below or email me directly.

A. cybotes juvenile. Photo courtesy of Thom Sanger

Apologies for the messiness of the formatting; this is my first blog post, and it only got here with a lot of technical support from JLo! History is full of examples of the little guy getting left behind. Unfortunately, so is the study of anoles. Most anole studies focus on adult lizards, and while there is certainly much to be learned from adult-focused studies, to ignore juveniles is to cheat ourselves of a great opportunity to better understand Anolis life history.

A. cybotes juvenile. Photo courtesy of Thom Sanger.

As readers of this blog likely appreciate, anoles are a model system for understanding evolution. To gain a comprehensive understanding of the factors that led to their stunning diversity, it’s important that we understand how selection acted upon these lizards at all stages of life – not just adulthood. A lizard has to survive from hatchling to reach adulthood and until we know more about how juveniles interact with their environment we cannot determine whether selection has shaped the juvenile stages with the same intensity as it has adult traits.

Thom Sanger wrote an earlier post that discussed the growth of Anolis limb length: “Growing Limbs – But Not the Kind With Leaves.” According to his post, variation in adult limb morphology can be traced “all the way back to the point in development when the cartilaginous long bone anlagen are just forming.”

This past summer, I worked with Thom, Michele Johnson (Trinity University), and Trinity undergraduates Ellee Cook and Diego Castro to study the morphology and behavior of juveniles on grounds of the Coral Sol Resort in Barahona, Dominican Republic. My goal was to understand whether juvenile lizards behave similarly to adults and whether juveniles have the same body proportions as adults.

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The cavalcade of new anole species continues with Gunter Köhler’s description of a new species, related to A. altae, from Costa Rica. The last few years have seen a steady progression of new species descriptions, almost all from Central and South America. Anolis must be pushing 400 species by now. Anyone got an up-to-date total?

And who’s described all these species? Rich Glor is in the midst of a five-part series identifying the big guns in Caribbean island species descriptions, but I reckon the mainlanders have been described by a very different crowd. Certainly in recent times Köhler, Poe and others must be up there, but it would be interesting to see who historically has been the most prolific. Perhaps a job for someone from Team Norops?

In any case, down to the nitty-gritty. What used to be known as A. altae has been divided now into seven allopatrically-distributed species at high elevations in Costa Rica.

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