Iguana insularis (Iguanidae) from the southern Lesser Antilles: An endemic lineage endangered by hybridization

Abstract

The newly described horned iguanaIguana insularis from the southern Lesser Antilles is separated in two easily recognized subspecies: I. insularis sanctaluciae from St. Lucia and I. insularis insularis from the Grenadines. Its former description is completed by the use of 38 new samples for genetic and morphological analysis. Seventeen microsatellites were used to estimate genetic diversity, population structure and the level of introgression with other Iguana species over nearly the whole range of the species. ND4 and PAC sequences were also used to better characterize hybridization and to complete the description of this lineage. The I. insularis population of St. Vincent shows a high level of introgression from I. iguana whereas in the Grenadines, most islands present pure insularis populations but several show evidence of introgressions. Of the two remaining populations of I. insularis sanctaluciae, only one is still purebred. The recent identification of this and other distinct insular species and subspecies in the eastern Caribbean, and evaluation of where hybridization has occurred, are timely and important because the native iguanas are in urgent need of conservation action. Among the greatest threats is the ongoing human-mediated spread of invasive iguanas from Central and South America, which are destroying the endemic insular lineages through multiple diachronic introgression events.

Forensic Genetic Analyses of Melanistic Iguanas Highlight the Need to Monitor the Iguanid Trade

“…Currently, IUCN guidelines designate I. delicatissima as ‘critically endangered’, whereas I. iguana is of ‘least concern’ [ 12 , 13 ]. Recently, several insular I. iguana populations in the Caribbean Lesser Antilles were proposed for full species recognition: I. insularis , constituting native populations from St. Lucia, St. Vincent and the Grenadines and Grenada, as well as I. melanoderma , which includes native melanistic populations from Saba, Montserrat, and St. Croix and St. Thomas [ 14 , 15 , 16 ]. However, these populations are currently designated as subspecies, with only I. iguana insularis (St. Vincent and the Grenadines and Grenada) and I. i. sanctaluciae (St. Lucia) recognized by the Iguana Taxonomy Working Group, whereas I. melanoderma is still considered part of I. i. iguana (for details, see ITWG [ 17 ]).…”

“…However, these populations are currently designated as subspecies, with only I. iguana insularis (St. Vincent and the Grenadines and Grenada) and I. i. sanctaluciae (St. Lucia) recognized by the Iguana Taxonomy Working Group, whereas I. melanoderma is still considered part of I. i. iguana (for details, see ITWG [ 17 ]). Although these remain currently unassessed under IUCN guidelines, the numerous threats faced by these island I. iguana populations is likely to result in them being designated as threatened [ 14 , 16 , 18 ].…”

An integrative approach to assess non-native iguana presence on Saba and Montserrat: are we losing all native Iguana populations in the Lesser Antilles?

“…Among these southern Lesser Antillean islands, non-native iguanas are also established on or have hybridized with native iguanas, namely on St. Lucia, St. Vincent, and several Grenadine islands (Fig. 1; Morton 2008;Breuil et al 2019Breuil et al , 2022. For Grenada, some evidence suggests non-native presence, but no samples have been analysed so far to con rm their presence and of potential hybridization (Breuil et al 2019).…”

“…Iguanas on St. Lucia, St. Vincent and the Grenadines were recently described as subspecies and later as the species Iguana insularis, with two subspecies (Breuil et al 2019(Breuil et al , 2022. The IUCN-SSC Iguana Specialist Group's Taxonomy Working Group (ITWG) currently does not recognize the proposed full species status, retaining the sub-species status, Iguana iguana insularis and I. i. sanctaluciae as originally described by Breuil et al (2019) until further evidence is published (Iguana Taxonomy Working Group 2022).…”

Choice of climate data influences current and future global invasion risks for twoPhelsumageckos

“…The increasing pace of reptile invasions, along with the associated ecological (e.g., trophic disruptions), evolutionary/conservation (e.g., through hybridisation or introgression), and sanitary costs (e.g. pathogen transmission) have led to a growing attention towards some species (Reed and Kraus 2010; Sauteur et al 2013; Kraus 2015; Vuillaume et al 2015; Bellinati et al 2022; Breuil et al 2022). However, invasive alien reptiles remain understudied compared to invertebrate and plant species (e.g., Bellard et al 2013) and there is a need to fill a knowledge gap in how climate change influences reptile invasion risks.…”