The global need to address threats from invasive alien iguanas

Madden²,

Debrot

2022

Preprint

Intraspecific diversity is among the most important biological variables, although still poorly understood for most species. Iguana iguana is a Neotropical lizard known from Central and South America, including from numerous Caribbean islands. Despite the presence of native melanistic I. iguana populations in the Lesser Antilles, these have received surprisingly little research attention. Here we assessed population size, distribution, degree of melanism, and additional morphological and natural history characteristics for the melanistic iguanas of Saba, Caribbean Netherlands based on a one-month fieldwork visit. Using Distance sampling from a 38-transect dataset we estimate the population size at 8233 ±2205 iguanas. Iguanas mainly occurred on the southern and eastern sides of the island, between 180-390 m (max altitude 530 m), with highest densities both in residential and certain natural areas. Historically, iguanas were relatively more common at higher altitudes, probably due to more extensive forest clearing for agricultural reasons. No relationship was found between the degree of melanism and elevation, and few animals were completely melanistic. Furthermore, we found that body-ratio data collection through photographs is biased and requires physical measuring instead. Although the population size appears larger than previously surmised, the limited nesting sites and extremely low presence of juvenile and hatchling iguanas (2.4%), is similarly worrying as the situation for I. delicatissima on neighboring St. Eustatius. The island's feral cat and large goat population are suspected to impact nest site quality, nest success, and hatchling survival. These aspects require urgent future research to guide necessary conservation management.

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Population estimate, natural history and conservation of the melanisticIguana Iguanapopulation on Saba, Caribbean Netherlands

Madden²,

Debrot

2022

Preprint

“…Despite its ‘least concern’ assignment, regional assessments across I. iguana indicate that local populations can be threatened due to a range of factors. Whereas mainland populations are also locally endangered [ 19 , 20 ], the most at-risk are insular populations in the Lesser Antilles, given a range of prominent threats, e.g., hunting, invasive species, and the spread of non-native iguanas [ 12 , 14 , 15 , 21 , 22 ]. Overall, I. iguana are among the most traded reptiles globally [ 23 , 24 ], with native populations being harvested for trade, often without restrictions [ 20 , 25 ].…”

Section: Introductionmentioning

confidence: 99%

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

Mitchell

Welch

2022

Animals

Lizards within the Iguana iguana species complex are among the most common reptilian pets, with the widest natural geographic range among iguanids. Deep phylogenetic divergence distinguishes multiple mitochondrial clades, and several taxonomic changes have recently been proposed. These small populations, typically island endemics, are threatened by numerous factors, including the international pet trade. Recent investigations reveal the absence of required CITES permits for lawful export of animals, providing evidence of ongoing illegal trade. Additional monitoring of trade in iguanas can be achieved through the application of forensic molecular techniques. In this study, two captive melanistic iguanas were genotyped for molecular markers for which geographic distributions of alleles have been established. Mitochondrial sequencing indicates that both animals carry a haplotype known to originate from the islands of Saba and Montserrat, populations taxonomically proposed to be Iguana melanoderma. Genotypes at 15 microsatellite loci are equally consistent with this origin, given the results of a principal component analysis. This first forensic genetic assessment within the extensive I. iguana pet trade highlights the presence of illegal activity. The need for additional forensic assessments of pet-trade iguanas is evident, especially given that their value is driven by variety and rarity, which is further intensified by recent taxonomic changes.

“…Within the Greater Caribbean region, insular iguana species are being impacted by recently-arrived nonnative iguanas (Knapp et al 2021). While on Little Cayman the intergeneric hybridization of the native Cyclura nubila caymanensis with non-native Iguana iguana is alarming (Moss et al 2018), the main invasive iguana hotspot is in the Lesser Antilles (Fig.…”

Section: Introductionmentioning

confidence: 99%

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

Goetz

Brannon

et al. 2022

Preprint

Invasive alien species are among the main drivers of the ongoing sixth mass extinction wave, especially affecting island populations. Although the Caribbean is well-known for its high species richness and endemism, also for reptiles, equally important is the regional contribution of non-native species to island biodiversity. The Lesser Antilles encompass high genetic diversity in Iguana, though most native populations either have gone extinct or are declining following competitive hybridization with invasive non-native iguanas. Here we assessed non-native presence in two poorly-studied native melanistic Iguana iguana populations using available genetic tools, and explored utilizing size-dependent body measurements to discriminate between native and non-native iguanas. Genetic samples from Saba and Montserrat were genotyped across 17 microsatellite loci with STRUCTURE and multivariate analyses indicating non-native iguanas presence only on Saba. This was corroborated by mtDNA and nDNA sequences, highlighting a non-native origin in Central America and the ABC islands. We identified preliminary evidence suggestive of hybridization. Morphological variation among size-dependent characteristics showed that non-native iguanas have significantly larger subtympanic plates than native iguanas. Non-native individuals also differed in scalation and coloration patterns. Overall, our findings demonstrate the need for continuous monitoring for non-native iguanas within remaining native Iguana populations in the Lesser Antilles, with those not directly threatened by non-native iguanas restricted to only 8.7% of the historic range. Although genetic data allows for identification of non-native or hybrid iguana presence, this field-to-lab workflow is time consuming. Rapid in-situ identification of non-native individuals is crucial for conservation management, and besides scale and coloration patterns, we have highlighted the utility of size-dependent variables for rapid diagnosis. We urge regional partners to build morphometric databases for native Iguana populations that will help to quickly detect future incursions of non-native iguanas and allow the rapid implementation of effective countermeasures during the early phase of invasion.