Robert W. Henderson

Molecular systematics and historical biogeography of tree boas (Corallus spp.)

Inferring the evolutionary and biogeographic history of taxa occurring in a particular region is one way to determine the processes by which the biodiversity of that region originated. Tree boas of the genus Corallus are an ancient clade and occur throughout Central and South America and the Lesser Antilles, making it an excellent group for investigating Neotropical biogeography. Using sequenced portions of two mitochondrial and three nuclear loci for individuals of all recognized species of Corallus, we infer phylogenetic relationships, present the first molecular analysis of the phylogenetic placement of the enigmatic C. cropanii, develop a time-calibrated phylogeny, and explore the biogeographic history of the genus. We found that Corallus diversified within mainland South America, via over-water dispersals to the Lesser Antilles and Central America, and via the traditionally recognized Panamanian land bridge. Divergence time estimates reject the South American Caribbean-Track as a general biogeographic model for Corallus and implicate a role for events during the Oligocene and Miocene in diversification such as marine incursions and the uplift of the Andes. Our findings also suggest that recognition of the island endemic species, C. grenadensis and C. cookii, is questionable as they are nested within the widely distributed species, C. hortulanus. Our results highlight the importance of using widespread taxa when forming and testing biogeographic hypotheses in complex regions and further illustrate the difficulty of forming broadly applicable hypotheses regarding patterns of diversification in the Neotropical region.

West Indian Herpetoecology

Publisher Summary This chapter discusses the herpetoecology of West Indian islands. The amphibians and reptiles of the region have proved to be ideal tools for research on ecology due to various qualities of the herpetofauna such as the intriguing distribution, wonderful diversity and the frequently high population densities. Several aspects of the ecology of the West Indian herpetofauna that made it especially attractive include its rich species diversity, trophic relations and versatility. West Indian islands collectively support one of the richest terrestrial vertebrate faunas in the Western Hemisphere. The herpetofauna represents the dominant vertebrate group in the West Indies with 169 amphibians and 453 reptiles of which 572 are endemic. Among the amphibians, 99% are endemic to the West Indies and 93% of reptiles are endemic to the area. Although many factors may be involved, larger West Indian islands harbor more species of amphibians and reptiles than do smaller islands. The West Indies harbor a rich anuran fauna, but it is a reptile-dominated vertebrate fauna and lizards especially predominate.

The Seasonal Incidence of Snakes at a Locality in Northern Belize

The effect of rainfall on Neotropical snake activity in general, in different adaptive zones and on seasonal differences in prey taken by snakes was studied utilizing 177 preserved specimens of 22 species collected in 19671974 in the area of Orange Walk Town, Belize. In addition, certain aspects of resource partitioning in a Neotropical snake community were examined. There is an apparent positive correlation between the number of snakes collected and amount of precipitation. The aquatic colubrid Tretanorhinus nigroluteus was, however, taken more often in the dry months than any other species and not at all in the peak of the rainy season. The number of snakes taken in each adaptive zone reaches a peak in September (the wettest month), or an equal number in September and another month, except for leaf litter and aquatic species. Stomach content analysis showed that 37.8% of the wet season and 22% of the dry season stomachs contained food. Anurans were the most common prey items, but they were not taken in the dry season. Snakes that did not prey on anurans were the ones most frequently taken in the dry season. Resource partitioning among the common anuran predators suggests that they are segregated either temporally or spatially. The Orange Walk snakes may or may not be directly rainfall dependent, but the prey (anurans) of many of them are directly rainfall dependent. Snake activity peaks in September and so, probably, does anuran activity. Many species of snakes hatch or are born in the wet season when anuran prey is most abundant and localized. The February-May inactive period is possibly induced by water loss and snakes might secrete themselves in damp, dark microhabitat in order to keep water loss to a minimum.

Foraging and diet in West Indian Corallus enydris (Serpentes: Boidae)

In the West Indies, the arboreal boid Corallus enydris usually forages from 1800 h to about 2400 h, and usually between 1-4 m above ground, but very large snakes (> 110 cm SVL) frequently forage at 110 cm SVL prey exclusively on endotherms. Although snakes > 75 cm SVL still prey on anoles, there is virtually no overlap in prey size with snakes < 75 cm SVL

An Overview Of Snake Conservation In The West Indies

No fewer than 120 snake species representing six families and 20 genera inhabit the West Indies; 115 (95.8%) are endemic to the region. Except for ± 30 taxa, we do not know the true conservation status of West Indian snakes; the herpetofauna is in a state of flux, as are the islands. Factors contributing to the decline of Antillean snake populations are complex, but nearly all are human-mediated and involve the introduction of exotic species, including predators (e.g., cats, black and Norway rats, mongooses) and ungulates (goats, pigs) that degrade habitats. Species that appear especially vulnerable to extirpations and extinctions are boids ( Epicrates spp.) and diurnal, ground-dwelling colubrids ( Alsophis spp. and Liophis spp.). Alterations in the prey base, commercial exploitation, and habitat destruction are likely responsible for declines in Epicrates populations, whereas predation by mongooses, cats, and rats have taken their toll on species of Alsophis and Liophis . Pesticides and herbicides may also have a deleterious impact on fossorial (e.g., Typhlops spp.) and anuran-eating species ( Antillophis spp., Chironius vincenti , Darlingtonia haetiana ). With greater environmental awareness and a minimum of tolerance, snakes and humans could co-exist.

Population Densities, Water-loss Rates, and Diets of Sphaerodactylus Vincenti on St. Vincent, West Indies

Abstract We documented population densities, microhabitat preferences, desiccation rates, and diets of Sphaerodactylus vincenti on St. Vincent, West Indies. We predicted and observed high densities (to 5,625/ha) in moist, shaded leaf-litter. Such microhabitats provide refuges, access to prey, and protection against water loss, because S. vincenti is vulnerable to high desiccation rates. We found significant differences in mass-specific water-loss rates and body mass between conspecific populations at differing elevations, with larger geckos less resistant to water loss living in more mesic environments at higher elevations. Stomach content analysis suggests that S. vincenti is a dietary generalist that feeds on a variety of small arthropods primarily by day.

The herpetofauna of Grenada and the Grenada Grenadines: Conservation concerns

Grenada and the politically associated Grenadines harbor 19 species of terrestrial herpetofauna, and four species of marine turtles either nest on their beaches or forage in the surrounding waters. The islands have a 2000-year history of human activity, but the past five centuries had the most adverse impact on the environment. Although some members of the herpetofauna have responded well to dramatically altered habitats (Anolis spp.), others have not (e.g., Eleutherodactylus euphronides). Similarly, the introductions of alien predators (most notably Herpestes javanicus) have likely impacted some species (e.g., Ameiva ameiva, Mabuya sp.), but not others. Several species appear to be genuinely rare (e.g., Clelia clelia, Typhlops tasymicris), and sharp declines in numbers have been documented for the arboreal boa Corallus grenadensis. The future of marine turtles in the area is threatened by habitat destruction (development of beachfront habitat for the tourist industry), slaughter of adults, and poaching of nests. Eco-tourism may hold the key for protection of forested habitats and the herpetofauna of this important group of islands.

Geographic Variation in the Emerald Treeboa, Corallus caninus (Squamata: Boidae)

Abstract The arboreal boa Corallus caninus is widely distributed across northern South America (the Guianas and Amazonia). We examined geographic variation based on examination of 192 specimens from throughout the range, and revised its taxonomy on the basis of quantitative and qualitative analyses of morphological characters (meristics, morphometrics, and color patterns). Based on the high number of lateral blotches on the body and the high number of scales across the snout, populations south of the Rio Amazonas and west of the Rio Negro are identified as a species (or, potentially, a species complex) separate from C. caninus, and the name Corallus batesii is resurrected for those populations. The distribution of Corallus caninus is restricted to the Guiana Shield (north of the Rio Amazonas and east of the Rio Negro).

A rapid assessment of herpetofaunal diversity in variously altered habitats on Dominica

In June 2008, we conducted a survey of Dominican herpetofaunal communities in habitats variously disturbed by human activity. Our rapid assessment found the highest abundance and species richness in moderately to substantially modified areas. We found relatively few species and low numbers of individuals in relatively natural high-elevation sites, dramatically altered urban areas, and active agricultural fields. In habitats subjected to intermediate levels of disturbance, such as a residential area and an inactive agricultural site invaded by dense exotic vegetation, complex physical habitat structure appeared to support the greatest herpetofaunal diversity. These results suggest that conservation efforts in the West Indies need not be restricted to pristine habitats, but also might include protection of slightly to moderately disturbed areas that may sustain greater biodiversity.

Microhabitat, activity, and density of a dwarf gecko ( Sphaerodactylus parvus ) on Anguilla, West Indies

Sphaerodactylus parvus is a dwarf gecko endemic to the Anguilla Bank in the Lesser Antilles, West Indies. Aspects of S. parvus ecology were studied at six sites on Anguilla. Geckos were encountered most frequently in association with rock spills, and gecko population densities (0-5.2/m 2 ) were correlated positively with rock densities. A disproportionate number of rocks which harbored S. parvus were on complex substrates of smaller rocks, leaf litter, and small sticks. Geckos became active in the late afternoon and early evening (after air temperature dropped below under-rock temperature). Activity peaked between 1900 h and 2100 h, but S. parvus was active in leaf litter until at least shortly past midnight. Potential problems associated with field studies of these diminutive gekkonids are discussed.