top of page
Mechanisms of Ecological Speciation
Prezygotic Isolation
Females exhibit preferences for male morphology
Assortative mating preferences are necessary for counteracting the homogenizing effects of gene flow during ecological speciation, yet little is known about how preferences evolve and contribute to total reproductive isolation between new species. Using a system of livebearing fishes that have independently colonized toxic sulfide springs in southern Mexico, I tested whether female Poecilia mexicana preferred CGI models of male fish with a body shape indicative of local adaptation. I found that females from non-sulfidic habitats exhibited a significant preference for CGI males with a non-sulfidic body shape. See our paper for more details on this study.
Genital morphology diverges during early stages of speciation
Divergence of genital traits among lineages has the potential to serve as a reproductive isolating barrier when copulation, insemination, and fertilization are inhibited by incompatibilities between female and male genitalia. We quantified genital variation in replicated population pairs of Poecilia mexicana with ongoing ecological speciation between sulfidic and nearby non-sulfidic habitats. We found evidence for rapid and correlated divergence of female and male genitalia across each of these evolutionarily independent population pairs exposed to divergent selection regimes, and both sexes exhibited convergent evolution of genital traits among populations inhabiting similar habitat types. These results demonstrate that genital evolution can occur during the early stages of speciation‐with‐gene‐flow and challenge the generality of previously suggested mechanisms of genital evolution in poeciliids. Check out our paper for the full study.
Postzygotic Isolation
Mitonuclear incompatibilities during ecological speciation
Hydrogen sulfide toxicity and detoxification are both associated with the oxidative phosphorylation (OXPHOS) pathway in the mitochondria. Adaptation to sulfidic environments has resulted in the modification of protein structures associated with OXPHOS for some lineages of Poecilia mexicana. Different parts of protein complexes associated with this pathway are encoded in either the mitochondrial or nuclear genomes. I am testing whether the break up of co-adapted mitochondrial and nuclear genes in hybrids between sulfidic and non-sulfidic populations results in either intrinsic or ecologically dependent declines in fitness. For this study, I am not only focusing on P. mexicana, but several other independent poeciliid population pairs occurring in sulfidic and non-sulfidic environments across the Americas and Caribbean (see Convergent Evolution page). I am attempting to quantify this potential postzygotic reproductive isolation using genomic datasets and protein structure modelling.
bottom of page