The Lesser Antillean Iguana (Iguana delicatissima) is an endangered species threatened by habitat loss and hybridization with non-native Green Iguanas (Iguana iguana). Iguanadelicatissima has been extirpated on several islands, and the Green Iguana has invaded most islands with extant populations. Information is essential to protect this species from extinction. We collected data on 293 iguanas including 17 juveniles from St. Eustasius, one of the few remaining I. delicatissima strongholds. Genetic data was leveraged to test for hybridization presence with the Green Iguana using both mitochondrial and nuclear genes, including 16 microsatellite loci. The microsatellites were also analysed to estimate genetic diversity, population structure and effective population size. Using molecular and morphological data we identified 286 I. delicatissima individuals captured during our first fieldwork effort, and seven non-native iguanas captured during a second effort, showing hybridization occurs within this population. Comparing homologous microsatellites used in studies on Dominica and Chancel, the I. delicatissima population on St. Eustatius has extremely low genetic diversity (HO=0.051; HE=0.057), suggesting this population is genetically depauperate. Furthermore, there is significant evidence for inbreeding (FIS=0.12) and weak spatial genetic structure (FST=0.021, p=0.002) within this population. Besides immediate threats including hybridization, this population's low genetic diversity, presence of physiological abnormalities and low recruitment could indicate presence of inbreeding depression that threatens its long-term survival. We conclude there is a continued region-wide threat to I. delicatissima and highlight the need for immediate conservation action to stop the continuing spread of Green Iguanas and to eliminate hybridization from St. Eustatius.
Door het toetreden van de eilanden Bonaire, Saba en St. Eustatius als bijzondere gemeenten tot het Koninkrijk der Nederlanden is de lijst met ‘Nederlandse’ reptielen en amfibieën uitgebreid. Meest bijzonder is de endemische Antilliaanse leguaan die op St. Eustatius voorkomt. Verschillende factoren zorgen er helaas voor dat de populatie gevaar loopt en van het eiland dreigt te verdwijnen. Ondanks populatieschattingen uit het verleden blijft het onduidelijk hoe klein en stabiel de populatie is. Het is dan ook van groot belang om de leguaanpopulatie te volgen. Daarom wordt nu voor het eerst de daadwerkelijke omvang van de populatie op St. Eustatius in kaart gebracht en staat monitoren op het beschermingsprogramma.
By joining the islands of Bonaire, Saba and St. Eustatius as special municipalities to the Kingdom of the Netherlands, the list of 'Dutch' reptiles and amphibians has been extended. Most special is the endemic Antillean iguana that occurs on St. Eustatius. Unfortunately, several factors cause the population to endanger and to disappear from the island. Despite population estimates from the past, it remains unclear how small and stable the population is. It is therefore of great importance to follow the iguana population. That is why for the first time the actual size of the population on St. Eustatius is being mapped and monitors are on the protection program.
With the accession of the islands of Bonaire, Saba and St. Eustatius as special municipalities of the Kingdom of the Netherlands, the list of ‘Dutch’ reptiles and amphibians has broadened. Of particular interest is the endemic Lesser Antillean Iguana which is native to St. Eustatius. Unfortunately, a range of factors has put the population of this iguana in danger of disappearing from the island. Despite estimates from the past, it remains unclear how small and viable the population is. Monitoring the population of the Lesser Antillean Iguana on St. Eustatius is therefore of the utmost importance. For the first time, the actual size of the population will be mapped and long-term monitoring has been added to the island’s conservation agenda.
This news article was published in BioNews 23.
BioNews is produced by the Dutch Caribbean Nature Alliance and funded by the Ministry of Economic Affairs.
Iguana delicatissima sightings on St. Eustatius, supported by RAVON (Reptiles, Amphibians and Fish Research Netherlands), STENAPA and the MSc theses of Thijs van den Burg (Vrije University Amsterdam) and Tim van Wagensveld (Wageningen University and Research).
See this report for more information on the survey.