Defining intraspecific conservation units in the endemic Cuban Rock Iguanas (Cyclura nubila nubila)

Kyle J Shaney,Ella Vázquez-Domínguez,Vicente Berovides-Álvarez,Sayra Espindola,Susette Castañeda-Rico,L Grisell Diaz-Ramirez

doi:10.1038/s41598-020-78664-w

Abstract

Defining conservation units is an important step in species management and requires interpretation of the genetic diversity and ecological function of the taxon being considered. We used the endemic Cuban Rock Iguanas (Cyclura nubila nubila) as a model to highlight this challenge and examined patterns of its intraspecific genetic diversity across Cuba. We evaluated nuclear (microsatellite loci) and mitochondrial diversity across eight populations from the island and its off-shore cays, and applied the population genetics results for assignment of Management Unit (MU) status and Evolutionary Significant Units (ESUs) based on phylogeographic and time of divergence information. We identified at least six distinct Cuban Rock Iguana MUs, encompassing demographically isolated and genetically differentiated populations across Cuba, most with low effective population size, declining populations, and with high risk of inbreeding and genetic drift. Hence, each MU should be considered of urgent conservation priority. Given the key ecological seed dispersal role of C. n. nubila, the disappearance of any MU could trigger the loss of local ecological functional diversity and major negative impacts on their ecosystems. Two divergent ESUs were also identified, exhibiting an historical east–west geographic separation on Cuba. Based on a Caribbean phylogeographic assessment, our findings strengthen the conclusion that all geographically and evolutionarily differentiated Cyclura species and subspecies across the archipelago warrant ESU distinction.

Highlights

Conservation of biodiversity is considered a top global priority[1]
No null alleles were consistently identified across loci and sampling localities, most loci were in Hardy–Weinberg equilibrium, and only the pair 152/154 from Cayo Macho showed linkage disequilibrium
Based on the population structuring obtained from microsatellite loci, we identified at least six different Cuban rock iguana Management Units (MUs) (Fig. 3), while based on the mitochondrial phylogeographic results and the estimated times of divergence, we propose that the Eastern and the Western phylogroups correspond to different Evolutionary Significant Units (ESUs)

Summary

Introduction

Conservation of biodiversity is considered a top global priority[1]. To combat biodiversity loss, conservation efforts have focused on preserving diversity at several levels, including whole ecosystems, species and genetically distinct intraspecific populations[2]. West Indian Rock Iguanas (genus Cyclura) of the Caribbean exhibit a high degree of endemism, with only one case of sympatry among recognized taxa[16] They are among the most critically endangered lizards in the world, primarily as a result of habitat degradation, direct human-hunting practices, introduction of invasive species, the population dynamics of small populations, and impending sea level rise[17,18]. All extant species are considered critically endangered, endangered or vulnerable by the I UCN21 and are protected under CITES (Appendix I) Despite their immediate conservation urgency and critical keystone ecological roles, we lack intraspecific genetic data for many Rock Iguana species, while their CU assignment and consideration of their ecological contribution in management strategies is currently n eeded[22]

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Conclusion