New species of skinks for T&T

Marisora aurulae 

Copeoglossum aurae

As of today the two species of skinks on Trinidad and Tobago have new genera and new epithets - they are newly described species. This is just a glimpse of changes to come in the herpetofauna of the islands. Many T&T species though to be widespread species are not, they are cryptic species that evolved in the islands or on the adjacent mainland. Below are parts of the species accounts for these new lizards from Hedges & Conn (cited below).


Copeoglossum aurae Hedges & Conn, 2012

Greater Windward Skink

Mabuia agilis—Boulenger, 1887:191 (part). Mabuia aenea—Garman, 1887:53 (part). Mabuya aenea—Barbour, 1914:322 (part). Mabuya aenea—Barbour, 1930:105 (part).

Mabuya mabouia—Barbour, 1935:129 (part). Mabuya mabouya mabouya—Dunn, 1936:544 (part). Mabuya mabouia—Barbour, 1937:147 (part). Mabuya aenea—Underwood, 1963:83 (part). Mabuya mabouya mabouya—Peters & Donoso-Barros, 1970:200 (part). Mabuya mabouya mabouya—Schwartz & Thomas, 1975:141 (part). Mabuya mabouya mabouya—MacLean et al., 1977:40–41 (part). Mabuya mabouya mabouya—Schwartz & Henderson, 1988:150 (part). Mabuya mabouya mabouya—Schwartz & Henderson, 1991:457 (part). Mabuya bistriata—Powell et al., 1996:82 (part). Mabuya bistriata—Murphy, 1997:150 (part). Mabuya sloanii—Mayer & Lazell, 2000:883 (part). Mabuya mabouya—Miralles, 2005:49 (part?). Mabuya nigropunctata—Miralles et al., 2005:833 (part). Mabuya nigropunctata—Miralles et al., 2009:609 (part). Mabuya mabouya—Henderson & Powell, 2009:292 (part).

Distribution. Copeoglossum aurae sp. nov. is distributed on Grenada, St. Vincent, the Grenadines (Bequia, Carriacou, Mustique, Petit Martinique, and Union Islands), Trinidad (including Huevos Island), and Tobago (Fig. 11D, I–J). The Union Island record is based on image identification (Fig. 25D). A DNA sequence from an uncataloged specimen collected on the nearby Peninsula de Paria (Sucre, Venezuela), reported by Miralles and Carranza (2010), clusters with this species in our tree (Fig. 5), indicating that the species also occurs on the mainland, possibly restricted to that peninsula. Previous distributional data in the literature (Murphy 1997; Daudin & de Silva 2007) cannot be used because it confounds C. aurae sp. nov. and Marisora aurulae sp. nov.

Ecology and conservation. No ecological information is available specifically for this species. Past ecological information reported for skinks from Trinidad and Tobago, summarized in Murphy (1997), probably confounds Copeoglossum aurae sp. nov. and Marisora aurulae sp. nov. In those reports, skinks were noted as occurring in a diversity of habitats, including rainforest, forest edge, coconut trash, and cultivated and disturbed areas. In the Grenadines, skinks have been found usually on the ground "in woody underbrush and between cacti" and climbing among cacti and on tree trunks (Daudin & de Silva 2007). According to Barbour (1937), skinks were already extirpated from the large islands of St. Vincent and Grenada by 1937, by the introduced mongoose. However, one specimen of C. aurae sp. nov. was collected in 1964 at Tempe, Grenada. Many herpetologists have visited Grenada and St. Vincent in the last four decades and no sightings of skinks have been reported. Circumstantial evidence suggests that black rats (Rattus rattus) are also predators, and these are on many islands. Skinks have not been extirpated from Trinidad, despite the presence of the mongoose on that island. In the past, Trinidad has had geological connections with South America and has a continental mammalian fauna that included natural predators of skinks, which may explain how they have survived (Murphy 1997). We identified more than twice as many specimens in museums of C. aurae sp. nov. than of Marisora aurulae sp. nov., suggesting that C. aurae sp. nov. is the more abundant species of the two. Now that these two species have been identified and described, studies are needed to assess their ecological relations and further clarify their conservation status. Based on IUCN Redlist criteria (IUCN 2011), we assess the conservation status of Copeoglossum aurae sp. nov. as Vulnerable (VU A2ace). It faces a primary threat from the introduced mongoose, which has probably led to its extirpation on Grenada and St. Vincent. Secondary threats include habitat destruction from agriculture and urbanization, and predation from other introduced predators, including black rats. Studies are needed to determine if the species still exists on Grenada and St. Vincent, the health of any remaining populations, and threats to the survival of the species.

Marisora aurulae Hedges & Conn, 2012

Lesser Windward Skink

Mabuia agilis—Boulenger, 1887:191 (part). Mabuia aenea—Garman, 1887:53 (part). Mabuya aenea—Barbour, 1914:322 (part). Mabuya aenea—Barbour, 1930:105 (part). Mabuya mabouia—Barbour, 1935:129 (part). Mabuya mabouya mabouya—Dunn, 1936:544 (part). Mabuya mabouia—Barbour, 1937:147 (part). Mabuya aenea—Underwood, 1963:83 (part). Mabuya mabouya mabouya—Peters & Donoso-Barros, 1970:200 (part). Mabuya mabouya mabouya—Schwartz & Thomas, 1975:141 (part). Mabuya mabouya mabouya—MacLean et al., 1977:40–41 (part). Mabuya mabouya mabouya—Schwartz & Henderson, 1988:150 (part). Mabuya mabouya mabouya—Schwartz & Henderson, 1991:457 (part). Mabuya bistriata—Powell et al., 1996:82 (part); Murphy, 1997:150 (part). Mabuya sloanii—Mayer & Lazell, 2000:883 (part). Mabuya mabouya—Miralles, 2005:49 (part?). Mabuya falconensis—Miralles et al., 2009:609 (part). Mabuya mabouya—Henderson & Powell, 2009:292 (part).

Distribution. The species is distributed in the southern Lesser Antilles and on Trinidad and Tobago. Specifically, it occurs on Young's Island (off St. Vincent), the Grenadines (Mayero Island, Carriacou, and Petit Bateau in the Tobago Cays), Grenada, Trinidad, and Tobago (Fig. 11D, I–J).

Ecology and conservation. Because of confusion between this species and the sympatric species Copeoglossum aurae sp. nov., published ecological information on skinks from the region cannot be applied to either species with certainty. Past ecological information reported for skinks from Trinidad and Tobago, summarized in Murphy (1997), probably confounds C. aurae sp. nov. and Marisora aurulae sp. nov. In those reports, skinks were noted as occurring in a diversity of habitats, including rainforest, forest edge, coconut trash, and cultivated and disturbed areas. In the Grenadines, skinks have been found usually on the ground "in woody underbrush and between cacti" and climbing among cacti and on tree trunks (Daudin & de Silva 2007). Apparently this species, and C. aurae sp. nov., have been extirpated from the large islands of St. Vincent and Grenada (Barbour 1937), both of which have the introduced mongoose. The mongoose is present on Trinidad, although C. aurae sp. nov. has been collected there in recent years (Murphy 1997); it may have adapted to continental mammalian predators on that island. Photographs of that species confirm its recent presence in the Grenadines (Fig. 25D). However, the last date of collection for M. aurulae sp. nov. on any island, from material we examined, was 1967 (Trinidad), although two specimens from Tobago (ZFMK 62602–03), not examined here, were collected more recently. Black rats (Rattus rattus) are also likely predators, and these are on many islands. We identified more than twice as many specimens in museums of C. aurae sp. nov. than of M. aurulae sp. nov., suggesting that M. aurulae sp. nov., over the years, has been less frequently collected (for whatever reasons) than C. aurae sp. nov.

Based on IUCN Redlist criteria (IUCN 2011), and considering that this species has not been seen on any island within its range (except Tobago, which is mongoose-free) in nearly a half-century, we assess the conservation status of Marisora aurulae sp. nov. as Critically Endangered (CR A2ace). It faces a primary threat from the introduced mongoose, which has apparently led to its extirpation from Grenada and Trinidad, and near-extinction. A secondary threat is predation from other introduced mammals, including black rats. Studies are needed to determine if the species still exists, the health of any remaining populations, and threats to the survival of the species. Captive breeding programs should be considered, if the species still exists, because eradication of introduced mammalian predators is not possible on large islands.

Citation

Hedges, S.B & C.E, Conn. 2012. A new skink fauna from Caribbean islands (Squamata, Mabuyidae, Mabuyinae). Zootaxa 3288:1-244.

An Overhaul of Caribbean Skink Systematics, new species, genera and families

The Neotropics are well known for their confused skink fauna composed of 26 species in the genus Mabuya, they have a conservative body plan, few conventional diagnostic characteristics, and are unique among lizards and other vertebrates in the degree of convergence, in reproductive traits, with eutherian mammals.

Blair Hedges and C. Conn of the University of Pennsylvannia have now revised the Caribbean skink fauna using conventional and unconventional morphological characters, supplemented by molecular analyses. They define 61 species grouped into 16 clades (=genera). The 16 genera include three available generic names (Copeoglossum, Mabuya, and Spondylurus) and 13 new genera: Alinea gen. nov., Aspronema gen. nov., Brasiliscincus gen. nov., Capitellum gen. nov., Exila gen. nov., Manciola gen. nov., Maracaiba gen. nov., Marisora gen. nov., Notomabuya gen. nov., Orosaura gen. nov., Panopa gen. nov., Psychosaura gen. nov., and Varzea gen. nov.

These 16 clades form a monophyletic group and are placed in the Subfamily Mabuyinae of the skink Family Mabuyidae. Six other skink families are recognized: Acontidae, Egerniidae, Eugongylidae, Lygosomidae, Scincidae, and Sphenomorphidae. The authors describe three new subfamilies of Mabuyidae: Chioniniinae subfam. nov., Dasiinae subfam. nov., and Trachylepidinae subfam. nov.; and 24 new species of mabuyines and resurrect 10 species from synonymies: Of the 61 total species of mabuyine skinks, 39 occur on Caribbean islands, 38 are endemic to those islands, and 33 of those occur in the West Indies. Most species on Caribbean islands are allopatric, single-island endemics, although three species are known from Hispaniola, three from St. Thomas, and two from Culebra, St. Croix, Salt Island, Martinique, the southern Lesser Antilles, Trinidad, and Tobago. Co-occurring species typically differ in body size and belong to different genera. Three ecomorphs are described to account for associations of ecology and morphology: terrestrial, scansorial, and cryptozoic. Parturition occurs at the transition between the dry and wet seasons, and the number of young (1–7) is correlated with body size and taxonomic group. Molecular phylogenies indicate the presence of many unnamed species in Middle and South America.

A molecular timetree shows that mabuyines dispersed from Africa to South America 18 (25–9) million years ago, and that diversification occurred initially in South America but soon led to colonization of Caribbean islands and Middle America. The six genera present on Caribbean islands each represent separate dispersals, over water, from the mainland during the last 10 million years. Considerable dispersal and speciation also occurred on and among Caribbean islands, probably enhanced by Pleistocene glacial cycles and their concomitant sea level changes. Based on IUCN Redlist criteria, all of the 38 endemic Caribbean island species are threatened with extinction.

Twenty-seven species (71%) are Critically Endangered, six species (16%) are Endangered, and five species (13%) are Vulnerable. Sixteen of the Critically Endangered species are extinct, or possibly extinct, because of human activities during the last two centuries. Several of the surviving species are near extinction and in need of immediate protection. Analysis of collection records indicates that the decline or loss of 14 skink species can be attributed to predation by the Small Indian Mongoose, an invasive predator introduced to control rats in sugar cane fields in the late nineteenth century (1872–1900), immediately resulting in a mass extinction of skinks and other reptiles. The ground-dwelling and diurnal habits of skinks have made them particularly susceptible to mongoose predation. 

The next post will discuss the changes impacting the T&T fauna.

Hedges, S.B & C.E, Conn. 2012. A new skink fauna from Caribbean islands (Squamata, Mabuyidae, Mabuyinae). Zootaxa 3288:1-244

Tobago's Melanistic Reptile Fauna

Melanism is the increase of the black pigment melanin, in the skin of animals. Melanin plays a role in several physiological processes including the synthesis of vitamin D; the protection of cells from harmful ultraviolet radiation; and it may be involved in the prervention of autoimmune diseases in humans. In cats, melanism may provide resistance to viral infections. And, at least one study suggests recessive-gene melanism is linked to disease resistance rather than altitude in cats.

However, despite extensive research, the function and adaptive significance of melanism remain controversial in reptiles. It is generally though that melanistic lizards and snakes, enjoy a thermal advantage compared with normal-colored individuals due to superior thermoregulatory capabilities. The often cited hypothesis is that melanistic individuals have a thermal advantage that lengthens daily and seasonal active allowing melanistic individuals to obtain more food, and a subsequent higher growth rate and larger body size. But, experimental evidence and observations suggests this is not the entire story (White et al. 2002; Tanaka 2009).

Tobago has several melanistc species, perhaps the best known is the tigre or tiger rat snake, Spilotes pullatus, but Pseudoboa neuwiedii also is darker on Tobago. Recently, John Jones from Huston Texas sent me this photo of an Ameiva atrigularis he took in central Tobago. It is remarkably dark for an Ameiva, and it would be interesting to know if all adults in this population are melanistic or this is just in this individual. Ugento and Harvey (2011) have described the sexual dimorphism in this species and have a photo of a specimen from the Isla de Margarita that looks very similar to this specimen.

Of interest is that all of these populations are at the northern edge of their distribution on Tobago.

Literature
Hardy, JD 1982. Biogeography of Tobago, West indies, with special reference to amphibians and reptiles: a review. Bulletin of the Maryland Herpetological Society 18:37-142.

Ugento, GN & Harvey, MB. 2011. Revision of Ameiva ameiva Linnaeus (Squamata: Teiidae) in Venezuela: recognition of four species and status of introduced populations in southern Florida, USA. Herpetological Monographs 25:113-170.

Tanaka K. 2009. Does the thermal advantage of melanism produce size differences in color-dimorphic snakes? Zoological Science. 26:698-703.

White A, Powell R, Censky EJ. 2002. On the thermal biology of Ameiva (Teiidae) from the Anguilla Bank, West Indies: Does melanism matter? Amphibia Reptilia 22:517-528.