One of the reasons that spot-lighting for anoles at nights works so well is that many anole species adopt a lighter color in the evening. This was first noted by Reverend Lockwood in an article in the American Naturalist in 1876 who noted that his captive anoles were usually brown during the day, even when on a green leaf, and were green at night, even when sleeping on brown surfaces. He concluded (p.13): “The belief that the color of the contiguous object is mimicked for the sake of protection is, I think, not confirmed by the observed facts. The truth is that in this matter of animals enjoying life there is a higher law than that of mere intention. I shall call it the law of spontaneous expression, which has its base in another law, to wit, that a joy unuttered is a sense repressed. Why should green be the favorite night-gown of our sleeping Anolis? I timidly venture the suggestion that it is because the animal is disposing itself for the luxury of sleep, its color changes being the utterances of its emotions . . . Whether it be the expression of enjoyment of repose, comfort, or emotional joy, the highest manifestation is its display of green.”
Anolis chlorocyanus basking on a clothesline in the Dominican Republic. Check out the parasites!
It was a long-standing paradigm in ecology that reptiles were consummate thermoconformers, essentially at the whim and mercy of environmental conditions. In 1944 this idea was challenged by seminal work by Cowles and Bogert who definitively demonstrated behavioral thermoregulation in lizards. This important paper sparked a series of new studies on the evolutionary ecology of thermoregulation. Researchers became interested in how lizards utilized different behavioral strategies under varying thermal regimes. They sought to explain and quantify the costs associated with thermoregulation in different environments, and understand how species richness on islands correlates with thermoregulatory strategy. The study by Cowles and Bogert was arguably one of the primary forces behind the “noose ’em and goose ’em” period of reptile biology.
This Jamaican twig anole, Anolis valencienni, was first described as Xiphocercus valencienni. Photo by Jonathan Losos
Asked Juliet of Romeo, “What’s in a name?” I pose a question to all the Anolis enthusiasts out there: Have you ever heard of the genus Xiphocercus? How about Audantia? As it turns out, several species recognized today as belonging to the genus Anolis were once placed into these defunct genera. For example, the twig anole A. valencienni was, for many years, known as Xiphocercus valencienni (Cope 1864) and, prior to that, as Anolis valencienni (Duméril and Bibron 1837), Dactyloa valencienni (Fitzinger 1843), Placopsis ocellata (Gosse 1850), and Anolis leucocephalus (Hallowell 1856). Obviously, before it was even known as Xiphocercus valencienni, the genus for this taxon was in flux.
Six years after publishing his impressive monograph on geographic variation in Anolis distichus, Schwartz published a similarly impressive monograph on geographic variation in Hispaniolan crown-giant anoles (Schwartz 1974). At the time this monograph was written, most authorities recognized a single polymorphic species of Hispaniola crown-giant anole with three subspecies: A. r. ricordii, A. r. baleatus, A. r. leberi, and A. r. barahonae (see my previous post on the spelling of ricordii if you’ve seen this name spelled with a single final “i” previously). However, as was the case with distichus, controversy was brewing before Schwartz’s monograph about whether these forms were best recognized at the specific or subspecific level and whether additional distinct forms had yet to be recognized within existing taxa.
The list sets out to honor naturalists who have lost their lives in the field or during other natural history pursuits. A lot of sad stories behind the names here, but a lot of epic ones too. I would bet that a great many of these fallen naturalists died doing what they loved best.
One of the names on the list is Ken Miyata, a young anole biologist who passed away in 1983. Ken was a student of Ernest Williams at Harvard’s Museum of Comparative Zoology in the late 70s (Ph.D. 1980), and he conducted fantastic work on anoles and other reptiles and amphibians, primarily in Ecuador. Although many of us probably know him for the mark he made on tropical herpetology during his brief career, Ken was much better known as a world-class fly fisherman, and it was that passion that ultimately killed him (see a brief retrospective here; see also these recent mentions of Ken by his old friends Jerry Coyne and Greg Mayer on the blog Why Evolution is True).
A name that’s missing from this wall is Preston Webster, another seminal anole biologist who died too young in a 1975 car crash. You can suggest additions to Conniff’s list in the comments of that blog, and he’ll add them. Does anyone who knew Webster want to put a few words on this site? I know very little about the man, but if there aren’t any takers, I’ll try to add him in a couple of days. I believe Webster was in the Dakotas when he died, and I don’t know if he was engaged in any ‘naturalist’s pursuits’ at the time (certainly not on anoles!). But this probably doesn’t matter – there are other great biologists on the list who died early in unrelated accidents.
There are several other herpetologists mentioned. Are there any other anole biologists missing from the list?
The figure above is a re-drawing from Schoener’s classic 1977 Biology of the Reptilia paper. Though “Competition and the Niche” has been widely cited, this figure, buried in the midst of the 102-page opus, has not gotten the attention it deserves. It shows that sexual size dimorphism in anoles is greatest on islands in which no other anole species are present and declines as function of the number of other anole species on an island. Anole community size is strongly correlated with island species richness, so this trend indicates that dimorphism and community richness are negatively related.
Map from http://www.costaricamapproject.com/InfoMaps/topographic.html
I’ve completed the brief survey of the distribution of A. cristatellus in Costa Rica (see previous post for explanation). The work was hampered by rainy and cool weather. Nonetheless, several new localities were identified. In particular, we found cristatellus in Bribri, very close to the Panamanian border. We actually went to the border town of Sixaolo, and even walked across the bridge, setting foot in Panama for a full 90 seconds (border officials apparently routinely allow tourists across the border to take a photo). However, by that time, the weather was very overcast and cool, and no lizards were out. Were I a betting man, I’d wager that cristatellus is already in the land of the canal.
Rand examined resource partitioning by seven Anolis species in Puerto Rico. Because of their general ecological similarity, Rand hypothesized that the anole species in Puerto Rico could only coexist if they had evolved (either in sympatry or allopatry) to partition available resources.
Morphologically, based on color, size, and body shape, he divided these seven species into 3 distinct groups: (1) Anolis evermanni and A. stratulus, (2) Anolis gundlachi and A. cristatellus, and (3) Anolis krugi, A. pulchellus and A. poncensis. These three groups would later be classified into the trunk-crown, trunk-ground, and grass-bush ecomorphs, respectively, on the basis of their similarity in habitat use, morphology, and behavior.
Rand showed habitat use partitioning among the species along two habitat axes: structural and climatic. He found that individuals of species that overlapped geographically divided the structural habitat, utilizing different perch heights and diameters. For example, A. evermanni, A. gundlachi, and A. krugi (all different ecomorphs) can be found in the same forest but the species use very different perches. In contrast, within an ecomorphological class (where individuals use similar perches), partitioning takes place along the climatic axis. For example, A. gundlachi and A. cristatellus, both trunk-ground ecomorphs, do not overlap in space. A. gunlachi occupies the shady forest while A. cristatellus inhabits sunny open fields and roadsides alongside the forest.
Rand’s paper is an Anole Classic for several reasons. First, by describing patterns in ecology, morphology, and behavior, this work helped set the stage for the ecomorph concept that Ernest Williams would coin in 1972. Second, Rand described two axes that explain a great deal of the diversity in habitat use by anoles. Third, it was the first paper to include perch diameter, in addition to perch height, as a descriptor of Anolis habitat use. Perch diameter has figured heavily in many subsequent studies of Anolis evolution as differences in perch diameter appear to drive differences in limb morphology among species. Last, Rand’s Figure 1 likely influenced Williams’s famous axes-of-diversification figure (Williams, E.E. 1983. Ecomorphs, faunas, island size, and diverse end points in island radiations of Anolis. In Lizard Ecology: Studies of a Model Organism. Eds. R.B. Huey, E.R. Pianka, and T.W. Schoener. Harvard University Press).
Figure from Lizards in an Evolutionary Tree, based on Webster and Burns (1973).
In a recent Anole Annals post, Luke Mahler mentioned the pioneering work of Webster and Burns on variation in the Hispaniolan trunk anole, A. brevirostris. This paper presents one of the most compelling cases for the occurrence of reinforcement—the phenomenon in which natural selection leads to the evolution of increased reproductive isolation when two hybridizing species come into sympatry. Surprisingly, however, this example is not well known; indeed, Google Scholar reports only 29 citations, only two of these post-1991. This is too bad, because it is a wonderful example and deserves to be more widely known. For this reason, I present a slightly modified description of variation in these lizards taken from Lizards in an Evolutionary Tree:
Three members of the A. brevirostris species complex, nearly indistinguishable in appearance, occur contiguously along the western coast of Haiti. The southernmost of these species is A. brevirostris itself, which has a light-colored, pale dewlap. By contrast, the northernmost species, A. websteri, has a vivid, orange dewlap. Most interesting, however, is the species sandwiched in between the other two, A. caudalis, whose dewlap color varies geographically: at the southern border of its range, near A. brevirostris, its dewlap is bright orange, and at the northern edge of its range, where it comes into contact with A. websteri, its dewlap is white. Interior populations exhibit variability in dewlap color with change occurring at least somewhat clinally from one end of the range to the other. Display behavior also differs among all three species, with the behavior of A. caudalis being the most distinct from the other two species. The most parsimonious explanation for these differences—particularly the geographic variation in dewlap color in A. caudalis—is that they evolved to prevent hybridization between closely related species. Indeed, electrophoretic analyses by Webster and Burns confirm that levels of gene flow are high among populations within each species, but extremely low or non-existent between species, including adjacent heterospecific populations.
