Archipelagic genetics in a widespread Caribbean anole

Abstract

Aim:We examine the influence of fluctuating sea levels in a land-bridge archipelago on the apportioning of intraspecific genetic diversity and divergence in the widespread Puerto Rican crested anole (Anolis cristatellus). We compare three alternative scenarios for genetic diversification in an archipelagic species that contrast the relative influences of periodic isolation versus island connectedness driven by fluctuating sea levels. Our approach combines information from geography and population genetics to assess the influence of island size, island isolation, island historical geography, and population genetic processes such as drift on the contemporary distribution of genetic variation within and among islands. Location: The Puerto Rico Bank in the Caribbean focusing primarily on the Spanish, British and U.S. Virgin Islands. Methods: We used nuclear and mitochondrial DNA sequences and microsatellite genotypes sampled from A. cristatellus populations to investigate: (1) the broad-scale pattern of phylogeographical divergence across Puerto Rico Bank islands and (2) diversification within the Virgin Islands archipelago. For the first component, we used sequence data to reconstruct the relationships among 542 samples from across the species range. For the second component, we examined the relative influences of island size, isolation, and population genetic processes on the distribution of genetic diversity across the Virgin Islands.Results: In the Virgin Islands, A. cristatellus is represented by a monophyletic clade except on the island of Vieques, where two divergent clades coexist. We found evidence for non-equilibrium dynamics in the Virgin Islands, suggesting spatial population expansion during intraglacial periods of low sea level. Main conclusions:We found limited evidence that periods of island isolation affected patterns of genetic diversity and differentiation. Instead, we found that the patterns of genetic diversity and divergence in A. cristatellus in the Virgin Islands archipelago are likely shaped by long-term persistence in the region and periods of population spatial expansion.

Patterns of morphological variation in the Schlegel’s Japanese gecko (Gekko japonicus) across populations in China, Japan, and Korea

“…This result is consistent with the results from allozyme data from nine G. japonicus populations in Japan, which showed high within-population genetic variation and little divergence among populations (Toda et al 2003). Similar trends were also reported in a morphometric study of Anolis sagrei in Florida (Lee 1992) and molecular studies of Urosaurus lizards (Haenel 2017) and Anolis cristatellus (Reynolds et al 2017). The small among-population variation observed in this study can be explained by either an insufficient time for local adaptation following recent population expansion in some populations, an early stage of multiple introductions from multiple source populations, or local morphological differentiation in similar urban habitats.…”

“…However, if the established population contains a certain degree of genetic diversity, allowing adaptation to new local environments, within-group variation could rapidly increase, leading to an overall increase in among-group variation (Bossdorf et al 2005;Lockwood et al 2005;Yang et al 2012a). On the other hand, in the case where there is insufficient time for local adaptation and/or in the very early stage of multiple introductions from multiple source populations, among-group morphological and genetic variation would be small (Haenel 2017;Reynolds et al 2017). Additional studies of natural situations are necessary to examine the relevant theoretical predictions for our better understandings of the evolutionary process following introductions of organisms.…”

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

“…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).…”

Biogeography, Systematics, and Ecomorphology of Pacific Island Anoles

“…We estimated the date of origin for each island species by analyzing our data using BEAST2. We used two approaches to estimating the age of divergence between each island lineage and its mainland relatives: (1) using the Macey et al [65] calibration rate of 0.65 mutations per 100 bp per million years, used by several mtDNA studies of anoles and related taxa [66][67][68][69][70][71] and (2) implementing the same mutation rate in addition to three calibration dates for Iguanian fossils used by Prates et al [37] and sources within. We used this approach following Román-Palacios et al's [24] findings that implementing multiple dating strategies can avoid the pitfalls of trees based only on a single mutation rate [72].…”