Anole species have been introduced to many places throughout the Caribbean and elsewhere (for example, Florida and Costa Rica), but relatively little research has examined the ecological impact of these invaders. Anolis carolinensis has been in the Ogasawara Islands of Japan for several decades, where it attains high population densities and has been blamed for local declines and even extinctions of native insects. It also is thought to negatively affect an endemic skink. Toda et al. report efforts to eliminate the green anole from port areas, so as to prevent them from stowing away and invading additional islands, and to reduce their population densities in other areas. They have found the most effective techniques to be putting out glue-traps designed for cockroaches (pictured here), which reduced anole densities by as much as 50% in some areas, and building Teflon-sided fences that anoles cannot climb. Efforts are continuing to eradicate these anoles and other invasive species on these islands. This paper also briefly reports a nice demographic study of the lizards, finding that some individuals could live longer than four years.
Category: New Research Page 65 of 67
What's that I hear? Photo by Melissa Losos
We think of anoles as visually oriented animals, but they can hear as well. Very little work has investigated their hearing ability, much less how they respond to aural phenomena. In a recent study, Huang et al. reported that anoles alter their behavior depending on what they hear. In particular, they show that A. cristatellus in St. John, U.S. Virgin Islands, appear to display less after hearing the call of a predatory bird, a kestrel, compared to their response to a non-threatening granivore, the bananaquit. They also report that simulated ecotourists playing the sound of a camera shutter clicking lead to a decrease in display rate compared to controls or the faux tourists taking flash photos. They interpret this finding as indicating that the sound of SLR cameras clicking, but not their flashes, are interpreted as a threat by the anoles. These results are interesting, but cry out for more thorough study, especially given that data were collected by approaching lizards, watching them for 1-2 minutes, presenting the stimulus, and then recording behavior for another minute and comparing rates of behavior from before and after. Moreover, differences in behavior among treatments were only detected in the final 15 seconds of the post-stimulus observation period, where no differences were detected in the first 45 seconds. Bottom line: it would be very interesting to investigate the role of hearing in anole behavior, and this study provides an inkling that there may be interesting work to be done.
Julián Velasco and colleagues recently added a new species to the anoles: Anolis anoriensis from the central Andes of Colombia, described in The Herpetological Journal. This species is placed in the aequatorialis group, and appears to be very similar to Anolis eulaemus, another Dactyloa group anole from the central Andes. Anolis anoriensis joins a host of recently described Andean anoles from this clade (e.g., Ayala-Varela and Velasco 2010; Ayala-Varela and Torres-Carvahal 2010 – see New Anole Literature for full citations) and adds to the incredible diversity of anoles in Colombia, which already boasts more recognized species than any other country. Despite these recent descriptions, the relationships of Andean anoles remain extremely poorly known, as does our understanding of the factors responsible for the generation of such diversity.
Anolis anoriensis (top panels) versus Anolis eulaemus (bottom panels), from Velasco et al. 2010
Since Darwin’s time, biologists have believed that evolution occurs at a very slow, glacial scale. A corollary of this belief is that ecologists need not consider evolution as they work out the intricacies of ecosystem functioning—it occurs much too slowly to be a factor in understanding the day-to-day interactions among species and their environment. In recent years, however, it has become apparent that, when natural selection is strong, evolutionary change can occur very quickly. This raises the possibility that ecological interactions can lead to rapid evolutionary change, which could then quickly have ecological effects. For example, several recent studies have shown that fish species will evolve adaptively in response to competitive and predatory interactions, and that these evolutionary changes affect the ecosystem, changing rates of primary production, decomposition and altering the biotic and abiotic composition of the ecosystem. The study of “eco-evolutionary dynamics” is taking off and was recently reviewed by Tom Schoener in Science. In that review, Schoener referred to ongoing research on Anolis sagrei in the Bahamas as an example of how ecological interactions could lead to evolutionary change that would then feedback and alter ecosystem properties (see above).
Little blue heron snacks on A. sagrei. Photo copyright bullfrog101, http://www.flickr.com/photos/43104350@N02/4463474718/sizes/l/in/photostream/
In the West Indies and southeastern U.S., the enormous population size of anole species makes them an important component of the ecosystem. In the rainforest of Puerto Rico, for example, the three most common anole species consume an estimated 450,000 insects per hectare. The flip side of this abundance is that anoles—small, not very fast, presumably tasty—may be an important food source for many other species. Indeed, most West Indian snakes eat anoles and, collectively, anoles constitute more than 50% of the diet of West Indian snakes. Similarly, many types of birds will eat anoles at least occasionally (e.g., 40% of the species at one study site in Grenada were observed eating anoles), and some species eat them in large numbers. In addition to birds and snakes, anoles seem to be eaten by just about any flesh-eating animal (or plant) big enough to do so. Other documented predators include many types of lizards (including many instances of cannibalism), dogs, cats, mongooses, frogs, katydids, tarantulas, spiders, whip scorpions, and centipedes (see Lizards in an Evolutionary Tree for citations and further discussion).
Despite the ecosystem importance of anoles, and particularly of predation on them, there is still a lot we don’t know about who eats anoles, when and how. For this reason, field studies are needed, and everyone should be encouraged to document observations they make. For example, a recent post on the “Anolis Lizard” page on Facebook provided a link to a video of a crab eating an unfortunate A. agassizi (itself a remarkable and little known species from Malpelo Island in the Pacific). I am unaware of any previous evidence of crab predation on anoles, and scavenging can be ruled out because the poor lizard is still alive. This situation may be atypical, though, because Malpelo is essentially one big rock, and thus the anoles are always on the ground.
Anolis sagrei amidst the seaweed. Photo courtesy David Spiller.
Traditionally, ecologists have studied food web interactions within particular habitats with the idea that what happens in Vegas stays in Vegas. The idea is that habitats are discrete entities and most ecological interactions occur among species within that habitat, rather than across habitats. In recent years, however, that view has been challenged by the recognition that organisms and resources can cross habitat boundaries. For example, when bears catch migrating salmon, the fish carcasses wash ashore, and the nutrients released from their decay—as well as from the bears pooping in the woods—can link the productivity of the oceans to the terrestrial realm. Increasingly, such cross-habitat/ecosystem interactions are being seen as having major effects on food web functioning.
In a pair of recent papers, the UC-Davis anole team reports elegant field studies on the role that the brown anole, A. sagrei, plays in mediating these effects.
Caribbean Herpetology is a new on-line, open-access journal edited by S. Blair Hedges (Pennsylvania State University), Robert Powell (Avila University), Robert Henderson (Milwaukee Public Museum), and Byron Wilson (University of the West Indies). On the basis of the content published thusfar, it seems devoted primarily to the publication of short notes on new distributional records, natural history observations, and discovery of species of conservation concern. For this type of work, Caribbean Herpetology seems like a nice alternative to Herpetological Review. [Note: I’m not sure if the journal has a stable URL, the link above takes you to caribherp, from which point you’ll need to click on the journal link to arrive at Caribbean Herpetology. The html code used to generate this page is beyond me, so perhaps someone else can tell us if there is a direct, stable link to the journal?].
With several colleagues, Cuba’s foremost authority on Anolis lizards – Lourdes Rodríguez Schettino – has recently published a paper on the anoles of Soroa that’s well worth checking out.
Soroa, in Pinar del Río, Cuba
Soroa is an unbelievable place. Although you wouldn’t guess it to be special for any particular reason – it’s a lower mid-elevation inland site in Cuba’s Pinar del Rio province – the place is lousy with anoles. There are a whopping 11 species there – on a visit you can see representatives of all six Greater Antillean ecomorphs in action, as well as several ‘boutique anoles’ – weirdos like the aquatic Anolis vermiculatus, or the ‘chipojo bobo’ Anolis (Chamaeleolis) barbatus that have no counterparts on other islands.
Soroa is a legendary site among anolefolk, and has been host to seemingly countless studies of anole ecology, doubtless due to the presence of a moderately comfortable resort on the premises. Lourdes Rodríguez Schettino and her students and colleagues regularly studied the natural history of Soroa’s anoles in the 80s and 90s (much of this work is summarized in an excellent 1999 book), and in the mid-90s, she hosted two joint Cuba-United States research expeditions to study anole community ecology there (Losos et al. 2003).
The famous Soroa waterfall (pretty tame in the middle of a 2008 drought)
Anolis aequatorialis from Ecuador
Caribbean anoles are renowned for the repeated evolution of ecomorphs, the same set of habitat specialists evolving independently on each island in the Greater Antilles. But what about in mainland Central or South America, where the majority of anole species occur? Mainland anoles have received relatively little research attention, particularly with regard to questions of ecomorphology (but see Alan Pounds’ fabulous paper from 1988), primarily because mainland species are both less abundant than Caribbean taxa as well as more cryptic, making data collection much more difficult. Mainland anoles are, as a first approximation, as diverse ecologically and morphologically as Caribbean anoles, and a preliminary study found that most mainland anoles do not fit neatly into any of the Caribbean ecomorph classes. Now, in a much broader study, Schaad and Poe compared the morphology of 255 species for seven morphological characters: snout-vent length, sexual size dimorphism, femur length, head length, lamella number, snout scale number, and the ratio of tail to snout-vent length. They found that very few species are, on morphological grounds, similar to Caribbean ecomorphs. Most of the species that do have similarity are, surprisingly enough, categorized as grass-bush anoles, although ecologically most of these species do not seem to use grass-bush habitats, from what we know of their ecology. This paper represents a good step forward in our understanding of the evolutionary diversification of mainland anoles, and how it compares to what has occurred in the Caribbean. The next step will not be so simple, however—getting habitat data for all these species.