Kirsten E. Nicholson

Evolution of Anolis Lizard Dewlap Diversity

Background The dewlaps of Anolis lizards provide a classic example of a complex signaling system whose function and evolution is poorly understood. Dewlaps are flaps of skin beneath the chin that are extended and combined with head and body movements for visual signals and displays. They exhibit extensive morphological variation and are one of two cladistic features uniting anoles, yet little is known regarding their function and evolution. We quantified the diversity of anole dewlaps, investigated whether dewlap morphology was informative regarding phylogenetic relationships, and tested two separate hypotheses: (A) similar Anolis habitat specialists possess similar dewlap configurations (Ecomorph Convergence hypothesis), and (B) sympatric species differ in their dewlap morphologies to a greater extent than expected by chance (Species Recognition hypothesis). Methodology/Principal Findings We found that dewlap configurations (sizes, patterns and colors) exhibit substantial diversity, but that most are easily categorized into six patterns that incorporate one to three of 13 recognizable colors. Dewlap morphology is not phylogenetically informative and, like other features of anoles, exhibits convergence in configurations. We found no support for the Ecomorph Convergence hypothesis; species using the same structural habitat were no more similar in dewlap configuration than expected by chance. With one exception, all sympatric species in four communities differ in dewlap configuration. However, this provides only weak support for the Species Recognition hypothesis because, due to the great diversity in dewlap configurations observed across each island, few cases of sympatric species with identical dewlaps would be expected to co-occur by chance alone. Conclusions/Significance Despite previous thought, most dewlaps exhibit easily characterizable patterns and colorations. Nevertheless, dewlap variation is extensive and explanations for the origin and evolution of this diversity are lacking. Our data do not support two hypothesized explanations for this diversity, but others such as sexual selection remain to be tested.

Adaptation, Speciation, and Convergence: A Hierarchical Analysis of Adaptive Radiation in Caribbean Anolis Lizards

Abstract Caribbean Anolis lizards are a classic case of adaptive radiation, repeated four times across islands of the Greater Antilles. On each island, very similar patterns of evolutionary divergence have occurred, resulting in the evolution of the same set of ecological specialists—termed ecomorphs—on each island. However, this is only part of the story of the Caribbean anole radiations. Indeed, much of the species diversity of Caribbean Anolis occurs within clades of ecomorphs, which contain as many as 14 ecologically-similar species on a single island. We ask to what extent the classic model of ecological interactions as the driving force in adaptive radiation can account for this aspect of anole evolutionary diversity. Our answer is that it can in part, but not entirely. More generally, the most complete understanding of evolutionary diversification and radiation is achieved by studying multiple hierarchical evolutionary levels from clades to populations.

Anole classification: A response to Poe

A recent correspondence (Poe 2013; hereafter referred to simply as ‘Poe,’ ‘he,’ or ‘his’) criticized our monographic revision of anole classification (Nicholson et al. 2012; hereafter referred to as ‘our’). In tone and content, Poe expresses his distress with the idea that his preferred concept of a single, large genus, containing all living members of the family Dactyloidae, might be divided into eight smaller genera. We acknowledge that science benefits from vigorous, intellectual debate, but would have preferred his commentary to be more constructive, objective, and scientifically accurate. We therefore present this rebuttal to explain how Poe erred in characterizing our work, and missed the opportunity to present an alternative comprehensive taxonomy to replace the one against which he argues so strenuously. In this contribution we explain, and correct, Poe’s errors and misrepresentations, and argue that our taxonomy is likely to be adopted because it 1) eliminates the obvious problem that will arise if the family Dactyloidae contains only a single large genus (i.e., that a single genus obscures the evolution and diversity within the group and misrepresents or cloaks it), 2) conforms with the long historical trend of dissecting large, cumbersome groups into smaller sub-units, 3) is consistent with all recent phylogenetic studies for anoles in membership within clades we recognize as genera, and 4) aids in associating these lizards with the ancient land masses that shaped their history.

A new species of Norops (Squamata: Polychrotidae) from northwestern Honduras

A new species of anole of the genus Norops is described from Departamento de Yoro in northwestern Honduras. The new species appears to be most closely related to members of the N. cupreus species group and is most easily distinguished from those species by male dewlap color and in having a single anterior nasal scale. Una nueva especie de anolito del genero Norops es descrita como proveniente del Departamento de Yoro en el noroeste de Honduras. La nueva especie, aparentemente en parentezco con los miembros del grupo N. cupreus, se diferencia de las otras especies de este grupo de especies mas facilmete por el color de la papera gular de los machos y por la presencia de una escama nasal anterior.

Translating a clade based classification into one that is valid under the international code of zoological nomenclature: the case of the lizards of the family Dactyloidae (Order Squamata)

In a tour-de-force for anole biology, Poe et al. (2017) provide the most complete phylogenetic analysis of members of the family Dactyloidae yet attempted. The contribution is remarkable in the completeness of sampled taxa and breath of included characters. It is equally remarkable in the concordance of their consensus tree with the topology of previous phylogenetic inferences. Thus, the creation of a near-complete data matrix of extant taxa demonstrates that an asymptote in tree topological stability likely was reached in previous studies with more limited sampling (e.g. Alfoldi 2011, Jackman et al. 1999, Nicholson et al. 2012). Such a result provides hope that major lineages within the anole radiation can be examined consistently by scientists interested in parsing evolutionary patterns emerging within and among them.

A new species of the genus Norops from Darién, Panama, with comments on N. sulcifrons (Cope 1899) (Reptilia, Squamata, Dactyloidae)

We describe the new species Norops triumphalis sp. nov. from Darién, Panama. Norops triumphalis differs from all congeners by having a combination of (1) smooth, bulging, subimbricate ventral scales; (2) a short tail, ratio tail length/SVL 1.54; (3) short hind legs, longest toe of adpressed hind leg reaching to ear opening, ratio shank length/SVL 0.24; (4) a lichenous body pattern; and (5) a very large yellowish orange dewlap in males. In external morphology, N. triumphalis is most similar to the species of the N. pentaprion group. Norops triumphalis differs from the other species in the N. pentaprion group, except N. sulcifrons, by having a very large orange male dewlap (vs. a large red or pink dewlap) and an unpigmented throat lining. Norops triumphalis differs from N. sulcifrons by having the supracaudal scales not forming a serrated crest (vs. a distinct serrated caudal crest present in N. sulcifrons), 4 supracaudal scales per segment (vs. 3 supracaudal scales per segment in N. sulcifrons), greatly enlarged outer postmental scales, about four times the size of adjacent medial scales (vs. moderately enlarged outer postmental scales, about twice the size of adjacent medial scales, in N. sulcifrons), and no enlarged postcloacal scales in males (vs. a pair of moderately enlarged postcloacal scales present in male N. sulcifrons). We further provide a standardized description and illustrations of the holotype of N. sulcifrons.

Lizards (Reptilia: Squamata) of the Corn Islands, Caribbean Nicaragua

The Corn Islands are two small Caribbean islands with the richest collection of endemic herpetofaunal taxa in Nicaragua. Despite increasing human population and associated habitat alteration, both islands lack protected areas. The lizard fauna of Great Corn Island consists of 14 species corresponding to nine families, and includes three endemic taxa. We collected three lizard species ( Corytophanes cristatus , Gonatodes albogularis , and Hemidactylus frenatus ) that were not previously recorded from that island. On Little Corn Island, where there were no previous records of lizards, we found seven species ( Ctenosaura similis , Gonatodes albogularis , Hemidactylus frenatus , Holcosus undulatus , Iguana iguana , Lepidodactylus lugubris , and Norops unilobatus ), all of which are also present on Great Corn Island.