American Society of Naturalists

A membership society whose goal is to advance and to diffuse knowledge of organic evolution and other broad biological principles so as to enhance the conceptual unification of the biological sciences.

“The roles of sexual and viability selection in the evolution of incomplete reproductive isolation: From allopatry to sympatry”

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Olivier Cotto and Maria R. Servedio

Contrasting forces on choosiness evolution often lead to the evolution of incomplete reproductive isolation

What are the mechanisms leading to reproduction between individuals from different species? Hybrids are commonly observed in the wild and result from incomplete reproductive preferences of individuals in well-characterized species. We know from previous research that imperfect reproductive preferences can be an evolutionary optimum when the encounter rate between incipient species is low. However, breeding often occurs in mating areas that are shared by closely related species, even though they spend most of their foraging time in different places. Olivier Cotto and Maria Servedio of the Biology Department at the University of North Carolina at Chapel Hill recently investigated how the geographical context of sister species can affect the evolution of reproductive isolation when mating choice is based on trait similarity between mating partners. They find that incomplete reproductive isolation can be a selected optimum in a wider range of scenarios than previously known, especially when hybrids have low fitness. When the encounter rate between incipient species varies within their range, incomplete reproductive preference tends to be favored where the encounter rate is low whereas complete reproductive isolation is favored when the encounter rate is high. The overall strength of reproductive preference results from the interaction between processes occurring in each locality. With this new research, Olivier Cotto and Maria Servedio propose a new avenue to understand apparent persistent hybridization between species and its variation across space and taxa. Read the Article