|Scientific Name:||Pholidoscelis corvinus (Cope, 1861)|
Ameiva corvina Cope, 1861
|Taxonomic Source(s):||Harvey, M.B., Ugueto, G.N. and Gutberlet Jr., R.L. 2012. Review of Teiid morphology with a revised taxonomy and phylogeny of the Teiidae (Lepidosauria: Squamata). Zootaxa 3459: 1-156.|
|Red List Category & Criteria:||Critically Endangered B1ab(iii,v)+2ab(iii,v) ver 3.1|
|Assessor(s):||Powell, R. & Daltry, J.C.|
|Contributor(s):||Milligan, H.T., Wearn, O.R., Wren, S., Zamin, T., Sears, J., Wilson, P., Lewis, S., Lintott, P., Powney, G., Hanson, S. & Hedges, B.|
|Facilitator/Compiler(s):||De Silva, R.|
Listed as Critically Endangered on the basis that this species has an extremely restricted distribution (somewhat less than 0.3 km2) which represents a single location at imminent risk from recently-established invasive mammals, and a near-future risk from an increased frequency of storm surges which are expected to result in a continuing decline in the extent and quality of vegetation on which this species depends.
|Previously published Red List assessments:|
|Range Description:||This species is endemic to Sombrero Island (Schwartz and Henderson 1991, Lazell 1964). This island, to the northwest of Anguilla, is the northernmost of the Lesser Antilles (Lazell 1964) and has a total area of approximately 0.366 km2.|
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||This species has been described as abundant throughout the island (Lazell 1964), and as "quite common" around the lighthouse and in areas where vegetation occurs (Shew et al. 2002). Lazell, however, also only investigated the area around the lighthouse. Surveys of the entire island indicate that it is much less widely-distributed than this author assumed, as it is confined to areas with vegetation (J. Daltry pers. comm. 2015). The total population in 1999, including juveniles, was estimated as being between 396 and 461, of which approximately 200 were mature adults, based on mark-recapture data (Daltry 1999). Several hurricanes have passed through the island subsequently, with Hurricane Lewis the largest to hit the island in recent times, and the impact of these on the species is unknown.|
|Current Population Trend:||Unknown|
|Habitat and Ecology:||This species is xerophilic and diurnal. It is ground-dwelling, however, it will climb pit walls for bird eggs and for basking sites (Lazell 1964). Sombrero Island is presumed to be of volcanic origin, however, it is capped with oceanic limestone (Lazell 1964). Vegetation cover is extremely sparse and consists of a few clumps of cactus, ground-trailing herbaceous plants, and small weeds. The species is at least seasonally food-limited. No amphibians or mammals occur on the island; however, large colonies of nesting sea birds are present, and the eggs of these are an important food source (Schwartz and Henderson 1991). The species occurs alongside two other known reptile species, a genetically distinct population of Anolis gingivinus and an undescribed Sphaerodactylus resembling S. sputator. The spread of exotic morning glory may be beneficial to the reptiles by increasing ground cover and supporting larger invertebrate populations (J. Daltry pers. comm. 2015).|
|Continuing decline in area, extent and/or quality of habitat:||Yes|
|Use and Trade:||There is no known use or trade in this species.|
There is no permanent human settlement on Sombrero. The British government had maintained a lighthouse there from about the 1860s, due to its position at the mouth of the Anegada Passage; the current lighthouse has now been decommissioned and human presence on the island is sporadic. A proposed launch pad was cancelled once the island's biological importance was recognized. Mice have now been reported from the island, apparently as an established population that has survived recent hurricanes. While the mice have been observed feeding on seabirds, which also provide food for the lizards, seabird colonies on the island are seasonal and there is a danger that increased rodent populations will lead to pressure on populations of all three lizard species, as well as competition for invertebrate prey, while birds are absent. While the rodents were thought to be confined to the area around the lighthouse, since 2014 this species has been encountered more widely (J. Daltry pers. comm. 2015).
While this species has been able to withstand the island being briefly flooded by a hurricane, it is unlikely it would survive complete permanent inundation due to sea level rise. Already there are reports that the island, which has a maximum elevation of 12 m, has been completely inundated by storm surges from major hurricanes, and modelling indicates that the frequency and intensity of hurricanes in the Caribbean will continue to increase. Storm surges remove most of the vegetation from the island periodically, which will impact this species.
|Conservation Actions:||There are no species-specific conservation measures in place for the species. Monitoring of the population numbers of this species is needed, because of its restricted distribution.|
|Amended reason:||This species was previously treated on the Red List under the genus Ameiva, but it is now placed under Pholidoscelis following Goicoechea et al. (2016), hence the need for this amended assessment.|
|Citation:||Powell, R. & Daltry, J.C. 2017. Pholidoscelis corvinus (amended version of 2016 assessment). The IUCN Red List of Threatened Species 2017: e.T174139A121640244.Downloaded on 23 February 2018.|
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