The Saban black iguana (''Iguana iguana melanoderma'') is a subspecies (sometimes considered a distinct species) of the green iguana thought to be

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found els ...

to the islands of

Saba Saba may refer to: Places * Saba (island), an island of the Netherlands located in the Caribbean Sea * Şaba (Romanian for Shabo), a town of the Odesa Oblast, Ukraine * Sabá, a municipality in the department of Colón, Honduras * Saba (river) ...

and Montserrat, although external evidence indicates that it may be distributed in other parts of the Caribbean. It was described in 2020 as a distinct species, although the

Reptile Database The Reptile Database is a scientific database that collects taxonomic information on all living reptile species (i.e. no fossil species such as dinosaurs). The database focuses on species (as opposed to higher ranks such as families) and has entri ...

classifies it as a subspecies of the common green iguana (''Iguana iguana'').

Taxonomy

The subspecies was previously considered to represent

melanistic The term melanism refers to black pigment and is derived from the gr, μελανός. Melanism is the increased development of the dark-colored pigment melanin in the skin or hair. Pseudomelanism, also called abundism, is another variant of pi ...

individuals of the green iguana. It was reclassified as a separate subspecies based on a number of genomic distinctions (private microsatellite alleles and unique mitochondrial ND4 haplotypes) and consistent morphological characteristics. Genetic evidence indicates that ''I. i. melanoderma'' is the

sister group In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

of the green iguana populations from

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the souther ...

(considered ''I. iguana iguana''), with both forming a clade that is the sister group of the green iguana populations present on

St. Lucia Saint Lucia ( acf, Sent Lisi, french: Sainte-Lucie) is an island country of the West Indies in the eastern Caribbean. The island was previously called Iouanalao and later Hewanorra, names given by the native Arawaks and Caribs, two Amerindia ...

and the

Grenadines The Grenadines is a chain of small islands that lie on a line between the larger islands of Saint Vincent and Grenada in the Lesser Antilles. Nine are inhabited and open to the public (or ten, if the offshore island of Young Island is counted) ...

, which are considered a distinct subspecies, '' I. i. insularis''. The

also recognizes the Saban black iguana as a distinct taxonomic entity, but due to its close relation to the green iguana, it (along with the two subspecies of ''I. insularis'') is instead classified as a subspecies of the green iguana, as ''I. i. melanoderma''.

Distribution

Iguana iguana en Zoologico de Barquisimeto

As proposed in the original publication, the subspecies displays a very unusual

disjunct distribution In biology, a taxon with a disjunct distribution is one that has two or more groups that are related but considerably separated from each other geographically. The causes are varied and might demonstrate either the expansion or contraction of a s ...

. Member populations are found on Montserrat and Saba, as well as on the

Virgin Islands The Virgin Islands ( es, Islas Vírgenes) are an archipelago in the Caribbean Sea. They are geology, geologically and biogeography, biogeographically the easternmost part of the Greater Antilles, the northern islands belonging to the Puerto Ric ...

and the island of

Vieques Vieques (; ), officially Isla de Vieques, is an island and municipality of Puerto Rico, in the northeastern Caribbean, part of an island grouping sometimes known as the Spanish Virgin Islands. Vieques is part of the Commonwealth of Puerto Rico ...

, and in northern

Venezuela Venezuela (; ), officially the Bolivarian Republic of Venezuela ( es, link=no, República Bolivariana de Venezuela), is a country on the northern coast of South America, consisting of a continental landmass and many islands and islets in ...

, including several coastal islets as well as the mainland vicinity of

Cumaná Cumaná () is the capital city of Venezuela's Sucre State. It is located east of Caracas. Cumaná was one of the first cities founded by Spain in the mainland Americas and is the oldest continuously-inhabited Hispanic-established city in South ...

. The mainland distribution has not been well defined. A news article indicated that it is believed the species was also present on

Redonda Redonda is an uninhabited Caribbean island that is a part of Antigua and Barbuda, in the Leeward Islands, West Indies. The island is about long, wide, and is high at its highest point. This small island lies between the islands of Nevis a ...

, but this was not addressed in the original publication; several authors have mentioned having seen iguanas, but no specimens have been collected, nor any fossils identified. Recent genetic insights confirm that near-indistinguishable melanistic iguanas (compared to Saba and Montserrat) have identical mitohondrial haplotypes as those two populations in the Lesser Antilles. Genetic data remains to be analyzed from the populations assigned to this subspecies in Venezuela. St Thomas Marriott Iguana 8

It is theorized that coastal Venezuela is the source population for ''I. i. melanoderma'' and also where it diverged from other iguanas. Three dispersal events have been proposed; one from coastal Venezuela to either Saba or Montserrat (with Montserrat being more likely if the dispersal was natural), a second

pre-Columbian In the history of the Americas, the pre-Columbian era spans from the original settlement of North and South America in the Upper Paleolithic period through European colonization, which began with Christopher Columbus's voyage of 1492. Usually, ...

dispersal from one of these two islands to the other, and a third to

Puerto Rico Puerto Rico (; abbreviated PR; tnq, Boriken, ''Borinquen''), officially the Commonwealth of Puerto Rico ( es, link=yes, Estado Libre Asociado de Puerto Rico, lit=Free Associated State of Puerto Rico), is a Caribbean island and Unincorporated ...

and the Virgin Islands. These dispersal events may have happened from natural dispersals, transport and introduction by

Amerindians The Indigenous peoples of the Americas are the inhabitants of the Americas before the arrival of the European settlers in the 15th century, and the ethnic groups who now identify themselves with those peoples. Many Indigenous peoples of the A ...

and/or European colonists, or both. As parts of its range may have been facilitated by human transport, its strange disjunct distribution may not be entirely natural in origin. A 2022 population estimate on Saba suggests that ~6000 iguanas occur on the island.

Description

The Saban black iguana is darker coloured than the other subspecies of green iguana, with colouration deepening in older individuals. It possesses a black

dewlap A dewlap is a longitudinal flap of skin or similar flesh that hangs beneath the lower jaw or neck of many vertebrates. More loosely, it can be various similar structures in the neck area, such as those caused by a double chin or the submandibu ...

, high dorsal spikes, no horns on the snout, and carries a noticeable black patch between the eye and tympanum. Although the Saban black iguana has been described as more darker than other subspecies, a recent population assessment of the Saba population indicated that only a small percentage of all adults become completely melanistic. While many iguanas become only partially melanistic, all had a black facial patch between the tympanum and eye.

Conservation

It has been suggested that the subspecies is threatened by unsustainable harvest for consumption and the pet trade, and by competition with and hybridization from escaped or released non-native iguana subspecies from the mainland. There have been plans to reintroduce the subspecies to Redonda, where it may have formerly occurred but was extirpated from. Iguanas from Saba have been illegally exported and subsequently traded using fraudulent

CITES CITES (shorter name for the Convention on International Trade in Endangered Species of Wild Fauna and Flora, also known as the Washington Convention) is a multilateral treaty to protect endangered plants and animals from the threats of interna ...

permits, and are currently offered as pets in numerous countries across the globe.

References

{{Taxonbar, from=Q94659710 Iguana Reptiles described in 2020 Reptiles of the Caribbean