Wednesday, April 15, 2020

[Herpetology • 2020] Iguana melanoderma Painted Black: A New Melanistic Endemic Species of Iguana Laurenti, 1768 (Squamata, Iguanidae) from Saba and Montserrat Islands (Lesser Antilles)

Iguana melanoderma
Breuil, Schikorski, Vuillaume, Krauss, Morton, Corry, Bech, Jelić & Grandjean, 2020

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

Figure 8. The dorsal carpet pattern of young adults Iguana melanoderma.
 A Montserrat B Saba. The dorsal coloration is formed by darker more or less interrupted dorso-ventral bands (brown, dark grey) on a lighter ground. This pattern disappears in old individuals. The black patch between the eye and the tympanum is already visible.

Figure 9. A Old adult Iguana melanoderma from Montserrat B old adult from Saba. In these old individuals the carpet pattern is absent. The head is almost entirely black, except for the top and the snout. The dewlap, neck, dorsal spikes, and forelimb are black. Dorsal and lateral coloring is more variable, ranging from entirely black to a mosaic of black, brown, and dark green scales.

Iguana melanoderma sp. nov.

Diagnosis: A species of Iguana, with a distinctive melanistic phenotype, with a black dewlap, huge tubercular nape scales, the absence of horns on the snout.

Etymology: The name was chosen to emphasize the most conspicuous feature of this new taxon, from melano meaning black and derma meaning skin.

Common local names are: Melanistic Lesser Antilles iguana, Saban Black iguana

Figure 10. Iguana melanoderma sunbathing at dawn on the Windward coast of Saba.

 Figure 11. A basking Iguana melanoderma optimizing after different trials its warming by a curved position when the sun is low on the horizon on the Windward coast of Saba.

Figure 1. Geographical distribution of the three iguana groups identified by Lazell (1973) in the 1960s and new taxonomic proposition. In the 1960s, the invasive iguanas from South America (Iguana iguana) were only present in the îles des Saintes and Guadeloupe (Basse-Terre) and formed the Central Group. Now, alien iguanas are present and breed on every bank (van den Burg et al. 2018b). The southern group is now considered to support two subspecies Iguana iguana insularis and Iguana iguana sanctaluciae (Breuil et al. 2019). The northern group is considered here as a new species.


 Michel Breuil, David Schikorski, Barbara Vuillaume, Ulrike Krauss, Matthew N. Morton, Elizabeth Corry, Nicolas Bech, Mišel Jelić and Frédéric Grandjean. 2020. Painted Black: Iguana melanoderma (Reptilia, Squamata, Iguanidae) A New Melanistic Endemic Species from Saba and Montserrat Islands (Lesser Antilles). ZooKeys. 926: 95-131. DOI: 10.3897/zookeys.926.48679