Iguana iguana insularis, Breuil & Vuillaume & Schikorski & Krauss & Morton & Haynes & Daltry & Corry & Gaymes & Gaymes & Bech & Jelić & Grandjean, 2019

Breuil, Michel, Vuillaume, Barbara, Schikorski, David, Krauss, Ulrike, Morton, Matthew N., Haynes, Pius, Daltry, Jennifer C., Corry, Elizabeth, Gaymes, Glenroy, Gaymes, Joanne, Bech, Nicolas, Jelić, Mišel & Grandjean, Frédéric, 2019, A story of nasal horns: two new subspecies of Iguana Laurenti, 1768 (Squamata, Iguanidae) in Saint Lucia, St Vincent & the Grenadines, and Grenada (southern Lesser Antilles), Zootaxa 4608 (2), pp. 201-232 : 208-212

Iguana iguana insularis nov. ssp.

Grenadines horned iguana, pink rhino iguana

Figs. 3–6 .

Holotype. The holotype of Iguana iguana insularis housed in MCZ under the numbers X-17620/R-79057 ( Fig. 3 ). This specimen was caught by James Lazell on Bequia, St Vincent & the Grenadines (10 April 1964).

Sex: Undetermined.

Age: Young, possibly 2 years old, based on its size.

Morphological measurements: Total length: 51.5 cm, SVL: 13.5 cm, tail length: 38 cm. Height and width of the left subtympanic plate: 3.2 mm, 4.3 mm.

Meristics: Number of gular spikes, 5 medium + 2 small. Number of dorsal spikes to cloaca: 54 ± 1.

Paratypes. Two other young specimens MCZ X-17619/R-79056 and X-17621/R-79058) from the same location and the same collector .

Diagnosis of Iguana iguana insularis ( Figs 4 , 5 ). We define the typical morphology of this new taxon based on our own observations on both adults and juvenile specimens on Palm and Union Islands (St Vincent & the Grenadines), complemented by the specimens from MCZ R-79056-57-58 collected on Bequia (also in St Vincent & the Grenadines) and R-79747 from Sandy Bay, Grenada. The latter four are young individuals with SVL from 128 mm to 135 mm, and thus lack some details specific to adults.

The iguanas from the Grenada Bank, including the Grenadines, are characterised by the following association of characters in adults compared with iguanas from Saint Lucia ( I. iguana sanctaluciae ssp. nov., see below).

– In most old adults (both males and females), the green colouration and black bands fade to an almost uniform light cream to nearly white, except on the posterior end of the tail where the black banding persists;

– In old adults, the head is nearly light cream to white;

– The dewlap is predominantly white but may have some black scales;

– There are no black margins on the subtympanic plate and on the sublabial scales;

– The snout has 2 to 5 median horns (usually 3 or 4) and 2 to 6 less developed lateral horns on each side;

– The horns may or may not remain black throughout the animal’s life;

– There are light yellow scales on the head and on the dewlap in old adults;

– The tips of the dorsal spikes of mature adults during the breeding season are light yellow to light orange;

– The anterior part of the dewlap is rounded.

Size. The largest purebred I. iguana insularis measured by the authors had an SVL of 45 cm (IGU77, an adult male on Palm Island, Fig. 4 ). Its tail was incomplete.

Another large individual fitting the morphology of this subspecies (but not genetically tested) on Petit Bateau had a total length of 136 cm.

Geographical distribution ( Fig. 6 ). Of the c. 30 islands of Grenada Bank, including the Grenadine islands and the main island of Grenada, 26 have been reported to have iguanas ( Henderson & Powell 2018). The entire bank is inferred to have been originally inhabited by I. iguana insularis but morphological (e.g. Henderson & Powell 2018, photograph p. 50) and genetic data indicate that several islands, including the main island of Grenada, have had incursions of iguanas from South American and/or Central American lineages.

From our collection of photographs of specimens captured by the authors and obtained from internet searches, it is clear that most Grenadine islands still have the indigenous white, horned and more or less black-banded phenotype, but there is the Central America phenotype with various hybrids among them that make it difficult to confirm which islands still have purebred populations of this subspecies. Further genetic testing is required to accurately map the present distribution of I. iguana insularis and invasive iguanas.

Etymology. The subspecific name refers to the numerous islands in the southern Lesser Antilles where the new subspecies lives.

Figures

FIGURE 3. Holotype of Iguana iguana insularis ssp. nov. MCZ X-17620/R-79057 © Museum of Comparative Zoology, Harvard University. © President and Fellows of Harvard College. Specimen in alcohol with discolouration. Annotations: 1. Small size of subtympanic plate ± 10-20% of the eardrum. 2. Two or three scales of decreasing size anterior to subtympanic plate. 3. Juxtaposed elongated sublabial scales 5. Median and lateral horns on the snout. 6. Horns with enlarged bases. 7. Oval and prominent nostrils. 9. Flat and triangular gular spikes. 10. Six gular spikes. 11. Scattered nuchal tubercles. 12. Low number of nuchal tubercles. 13. Small size of nuchal tubercles. 15. Dewlap of medium size.

FIGURE 4. Examples of adult male Iguana iguana insularis ssp. nov.A. Adult male (Palm island) sequenced under the number IGU75 (SVL 41 cm); B and C, adult male (Palm Island) sequenced under the number IGU77 (SVL 45 cm) (Palm Island). Annotations: 1. Small size of subtympanic plate ± 10-20% of the eardrum. 2. Two or three scales of decreasing size anterior to subtympanic plate. 3. Juxtaposed elongated sublabial scales. 4. No apparent swelling of the jowls in breeding males. 5. Median and lateral horns on the snout. 6. Horns with enlarged bases. 7. Oval and prominent nostrils. 8. Brown eyes with visible white. 9. Flat and triangular gular spikes. 10. Seven or eight gular spikes. 11. Scattered nuchal tubercles. 12. Low number of nuchal tubercles. 13. Small size of nuchal tubercles. 14. Orange in dorsal scales in breeding animals. 15. Creamy white dewlap of medium size. 16. Creamy white body with faint to no black banding in old individuals.

FIGURE 5. Nasal horns of Iguana iguana insularis ssp. nov. View of the snout of IGU75 (A) and IGU77 (B) from Palm Island (same individuals as Fig. 4). Annotations: 0. Frontal scale not developed into a horn. 1. Median horns with enlarged bases. 2. Lateral horns. 3. Oval prominent nostril. Note the differing forms and disposition of cephalic scales, and that IGU75 (a younger male) has flat scales whereas IGU77 (an older, larger male) has more prominent scales.

FIGURE 6. Distribution of iguanas in the Grenadine islands. Locations are mapped to the nearest 2 × 2 km square representing groups of islands in the Grenadines. We have deliberately avoided being specific to protect the animals (see Auliya et al. 2016). Note that there are alien iguanas on some islands and not all of the island clusters shown here have purebred populations of Iguana iguana insularis. We have no confirmed specific localities for the main island of Grenada, although a museum specimen (MCZ R-79747) confirms this subspecies occurred here. Henderson & Breuil (2012), Henderson & Powell (2018), Baldwin (2012) and Baldwin & Mahon (2011), G. Gaymes and J. Daltry (pers. obs.; the Grenadines). While iguanas are present on St. Vincent, these have not been identified to subspecies level and cannot be assumed to be identical to those on the Grenada Bank. The grey line just south of St Vincent marks the brake between the St. Vincent Bank to the north and the Grenada Bank to the south. The black line between Petit Saint Vincent and Petit(e) Martinique shows the political boundary between St. Vincent and the Grenadines to the north and Grenada to the south. The Grenadine islands form an archipelago from the south of St. Vincent to the north of Grenada.