Abstract
In allopatric species, reproductive isolation evolves through the accumulation of genetic incompatibilities. The degree of divergence required for complete reproductive isolation is highly variable across taxa, which makes the outcome of secondary contact between allopatric species unpredictable. Since before the Pliocene, two species of Anolis lizards, Anolis carolinensis and Anolis porcatus, have been allopatric, yet this period of independent evolution has not led to substantial species‐specific morphological differentiation, and therefore, they might not be reproductively isolated. In this study, we determined the genetic consequences of localized, secondary contact between the native green anole, A. carolinensis, and the introduced Cuban green anole, A. porcatus, in South Miami. Using 18 microsatellite markers, we found that the South Miami population formed a genetic cluster distinct from both parental species. Mitochondrial DNA revealed maternal A. porcatus ancestry for 35% of the individuals sampled from this population, indicating a high degree of cytonuclear discordance. Thus, hybridization with A. porcatus, not just population structure within A. carolinensis, may be responsible for the genetic distinctiveness of this population. Using tree‐based maximum‐likelihood analysis, we found support for a more recent, secondary introduction of A. porcatus to Florida. Evidence that ~33% of the nuclear DNA resulted from a secondary introduction supports the hybrid origin of the green anole population in South Miami. We used multiple lines of evidence and multiple genetic markers to reconstruct otherwise cryptic patterns of species introduction and hybridization. Genetic evidence for a lack of reproductive isolation, as well as morphological similarities between the two species, supports revising the taxonomy of A. carolinensis to include A. porcatus from western Cuba. Future studies should target the current geographic extent of introgression originating from the past injection of genetic material from Cuban green anoles and determine the consequences for the evolutionary trajectory of green anole populations in southern Florida.
Highlights
In allopatric species, reproductive isolation evolves through the accumulation of genetic incompatibilities in geographically separated lineages (Dobzhansky, 1937; Orr, 1995)
The degree of divergence required for complete reproductive isolation is highly variable across taxa, which makes the outcome of secondary contact between allopatric species unpredictable
Future studies should target the current geographic extent of introgression originating from the past injection of genetic material from Cuban green anoles and determine the consequences for the evolutionary trajectory of green anole populations in southern Florida
Summary
Reproductive isolation evolves through the accumulation of genetic incompatibilities in geographically separated lineages (Dobzhansky, 1937; Orr, 1995). When reproductive barriers are weak, secondary contact between previously isolated lineages (e.g., native and introduced species) can lead to hybridization (Prentis, Wilson, Dormontt, Richardson, & Lowe, 2008; Schierenbeck & Ellstrand, 2009), rapidly homogenize parental genotypes, erode species boundaries (Glotzbecker, Walters, & Blum, 2016; Hasselman et al, 2014; James & Abbott, 2005; Ward et al, 2012), and threaten the genetic integrity of native species (Brennan et al, 2015; Jiggins & Mallet, 2000). We use multilocus nuclear genotypes and mitochondrial haplotypes to distinguish between contemporary and past gene flow, allowing us to test whether secondary contact has eroded putative species boundaries or whether the two sister species are reproductively isolated and coexist as genetically distinct taxonomic units
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
