endemic

Accurate assessment of species ranges is important not only for conservation planning but also for our understanding of their ecology and evolution (e.g., Kodric-Brown and Brown, 1993; Carlton, 1996; Blackburn and Gaston, 1998; Rondinini et al., 2006). Although several Lesser Antillean reptile groups show high levels of endemism, with most islands hosting at least one local endemic species (Lazell, 1972; Hedges et al., 2009; Tucker et al., 2017), it is not uncommon for Sphaerodactylus geckos to range across multiple islands (Schwartz and Henderson, 1991; Thorpe et al., 2008; Surget-Groba and Thorpe, 2012; Yuan et al., 2020). The Island Least Gecko, Sphaerodactylus sputator (Sparrman, 1784), is known to occur on the islands of Anguilla, St. Barthélemy, St. Eustatius, St. Kitts, St. Martin, and Nevis, as well as their satellite islands (King, 1962; Schwartz and Henderson, 1991; Malhotra and Thorpe, 1999; Powell et al., 2005; Questel, 2012, 2018). Here, we confirm the presence of S. sputator on Saba, from where, to the best of our knowledge, the species has not previously been reported (Schwartz and Thomas 1975; Schwartz and Henderson, 1991; Powell and Henderson 1996; Powell et al., 2005; Powell and Bauer 2012; Powell and Henderson 2012).

Abstract

The Lesser Antilles, in the Eastern Caribbean, is inhabited by three Iguana species: the Lesser Antillean iguana Iguana delicatissima, which is endemic to the northernmost islands of the Lesser Antilles, the introduced common iguana from South America, Iguana iguana iguana, represented also by the two newly described endemic subspecies Iguana iguana sanctaluciae from Saint Lucia and Iguana iguana insularis from Saint Vincent and the Grenadines, and Grenada, and the introduced Iguana rhinolopha from Central America. Drawing on both morphological and genetic data, this paper describes the Iguana populations from Saba and Montserrat as a new species, Iguana melanoderma. This species is recognized on the basis of the following combination of characteristics: private microsatellite alleles, unique mitochondrial ND4 haplotypes, a distinctive black spot between the eye and tympanum, a dorsal carpet pattern on juveniles and young adults, a darkening of body coloration with aging (except for the anterior part of the snout), a black dewlap, pink on the jowl, the high number of large tubercular nape scales, fewer than ten medium sized–triangular dewlap spikes, high dorsal spikes, and lack of horns on the snout. This new melanistic taxon is threatened by unsustainable harvesting (including for the pet trade) and both competition and hybridization from escaped or released invasive alien iguanas (I. iguana iguana and I. rhinolopha) from South and Central America, respectively. The authors call for action to conserve Iguana melanoderma in Saba and Montserrat and for further research to investigate its relationship to other melanistic iguanas from the Virgin Islands and coastal islands of Venezuela.

Keywords: Conservation Biology, Iguana, Lesser Antilles, microsatellites, mtDNA, new endemic species, phylogeny