Colonization of islands in the Mona Passage by endemic dwarf geckoes (genus Sphaerodactylus) reconstructed with mitochondrial phylogeny

Abstract

Little is known about the natural history of the Sphaerodactylus species endemic to the three islands located in the Mona Passage separating the Greater Antillean islands of Hispaniola and Puerto Rico. In this study, parts of two mitochondrial genes, 16S rRNA and 12S rRNA, were sequenced to determine the relationships between the sphaerodactylids that live in the Mona Passage and other Caribbean species from the same genus. While the main goal was to identify the biogeographical origin of these species, we also identified a genetically distinct type of dwarf gecko that warrants future evaluation as a possible new species. According to the reconstructed phylogenies, we propose a stepwise model of colonization wherein S. nicholsi from southwestern Puerto Rico or a very close ancestor gave rise through a founder event to Sphaerodactylus monensis on Mona Island. In a similar fashion, S. monensis or a very close ancestor on Mona Island gave rise to S. levinsi on Desecheo Island. This study also suggests that the most recent common ancestor between the species from the islands in the Mona Passage and Puerto Rico existed approximately 3 MYA.

Persistence of a Geographically-Stable Hybrid Zone in Puerto Rican Dwarf Geckos

“…Furthermore, S. nicholsi and S. townsendi are not sister taxa and an S. nicholsi sensu lato that includes a synonymized S. townsendi would be rendered paraphyletic by both S. monensis and S. levinsi (Figure 1a). However, these results do conflict with the only previously published molecular genetic phylogeny for this group, which found S. townsendi samples nested deep within S. nicholsi to the exclusion of both S. monensis and S. levinsi (Díaz-Lameiro et al 2013). To resolve this discrepancy, we briefly reanalyzed Díaz-Lameiro et al's (2013) 16S sequence data but added several vouchered S. townsendi specimens we collected from populations allopatric with respect to S. nicholsi.…”

“…To resolve this discrepancy, we briefly reanalyzed Díaz-Lameiro et al's (2013) 16S sequence data but added several vouchered S. townsendi specimens we collected from populations allopatric with respect to S. nicholsi. This revised phylogeny indicates the 2 S. townsendi specimens used in Díaz-Lameiro et al (2013) were misidentified S. nicholsi (Supplementary Figure 9). Thus, resolving this phylogenetic discrepancy and rejecting the hypothesis that S. townsendi and S. nicholsi form a clade to the exclusion of S. monensis and S. levinsi.…”

“…These questions can be answered by collecting S. nicholsi and S. townsendi from their entire current distributions. By examining the phylogenetic relatedness between populations and each population's historical demography, a plausible biogeographic scenario could be constructed to ascertain the approximate time since these species came into secondary contact (Díaz-Lameiro et al 2013;Reynolds et al 2017;Pinto et al 2019). The second line of evidence would attempt to corroborate the proposed date of secondary contact and the specific age of the hybrid zone by using calculations of linkage disequilibrium to estimate how many generations have passed since the establishment of the hybrid zone (Schumer et al 2014).…”

“…Of these, 4 currently recognized Puerto Rican (PR) Sphaerodactylus species have been hypothesized to be closely related: S. nicholsi, Sphaerodactylus townsendi, Sphaerodactylus monensis, and Sphaerodactylus levinsi (Grant 1931(Grant , 1932aHeatwole 1968). However, the taxonomic status and phylogenetic relationships between these species have been debated, without conclusion, since their description-based on both morphological and genetic data (Grant 1931;Thomas and Schwartz 1966;Murphy et al 1984;Hass 1991;Díaz-Lameiro et al 2013). While the taxonomic status of S. monensis and S. levinsi has remained relatively stable (occurring allopatrically on the islands of Mona and Desecheo, respectively), the relationship and taxonomic status of S. nicholsi, with regard to S. townsendi, have been somewhat contentious.…”

Genetic divergence and diversity in the Mona and Virgin Islands Boas, Chilabothrus monensis (Epicrates monensis) (Serpentes: Boidae), West Indian snakes of special conservation concern

“…Díaz-Lameiro et al, 2013;Rodríguez-Robles et al, 2007), and421 Chilabothrus boas could have also reached Mona in this manner.422 The disjunct range of C. monensis s.l. (Fig.…”