A story of nasal horns: A new species ofIguanaLaurenti, 1768 (Squamata, Iguanidae) in Saint Lucia, St Vincent & the Grenadines, and Grenada (Southern Lesser Antilles) and its implications for the taxonomy of the genusIguana

Abstract

The Lesser Antilles, in the Eastern Caribbean, were long considered to have only two species in the genusIguanaLaurenti 1768: the Lesser Antillean iguanaIguana delicatissima, which is endemic to parts of the Lesser Antilles, and the common green iguanaIguana iguana, which also occurs throughout Central and South America. However, herpetologists and reptile collectors have pointed out strong physical differences between some of the island populations ofIguana iguanaand those from the continent. Drawing on both morphological and genetic data, this paper describes a third speciesIguana insularissp. nov. from the southern Lesser Antilles, specifically the countries of Saint Lucia, St Vincent & the Grenadines, and Grenada. The new species is described based on the following unique combination of characters: Presence of high median and medium to small lateral horns on the snout; Small subtympanic plate not exceeding 20% of the eardrum size; Two or three scales of decreasing size anterior to the subtympanic plate; Fewer than ten small to medium triangular gular spikes; Medium sized dewlap; Low number of small to medium dispersed nuchal tubercles; Dark brown iris, with the white of the eye visible; Oval, prominent nostril; Short and relatively flat head; High dorsal spines; No swelling of the jowls in reproductively active males; Colour of head, body and tail changing from green to pale grey or creamy white in old adults; Vertical black stripes on body and tail, fading with age in some populations. This paper furthermore distinguishes two subspecies:Iguana insularis insularisfrom the Grenada Bank (comprising Grenada and the Grenadine islands), andIguana insularis sanctaluciaefrom Saint Lucia. The form on the island of Saint Vincent has not been identified. Both subspecies are globally threatened by unsustainable hunting (including the pet trade) and by invasive alien species, including hybridization from invasive iguanas from South and Central America (I. iguanaandI. rhinolopha, considered here as full species) that have become established in all three countries. The authors call for stronger measures to conserve the remaining purebredIguana insularissp. nov. throughout its range and for further research to identify other cryptic species and subspecies ofIguanain the Lesser Antilles.