The Evolution of Sexual Isolation via Sexual Selection in Sticklebacks. Jenny Boughman Associate Professor Michigan State University.

Título:The Evolution of Sexual Isolation via Sexual Selection in Sticklebacks

Ponente: Jenny Boughman. Associate Professor, Zoology; Ecology, Evolutionary Biology & Behavior; BEACON Center for the Study of Evolution in Action, Michigan State University

Resumen:
Sexual selection is a powerful evolutionary force, causing dynamic trait evolution that can result in isolation between diverging populations. Whether sexual selection causes speciation is controversial, but stickleback fish have provided a compelling case study. I weave together new evidence on female choice and male competition, showing how they contribute to speciation. First, I focus on female preference. Female preferences for ecologically relevant male traits may be important both for within and between species mate choice. Within species, these preferences allow females to choose high quality, locally adapted males, while between species, they allow females to avoid costly heterospecific matings. Such preferences for traits that indicate local adaptation may also lead to the evolution of magic traits that can greatly facilitate speciation. We studied female mate preference for body size and body shape, both of which are ecologically important traits in benthic, limnetic and anadromous threespine sticklebacks. We find evidence that female preferences have diverged to prefer locally adapted males. In conspecific mating trials benthic females preferred larger males, while limnetic females preferred males that were more limnetic-like in shape. In heterospecific mating trials, surprisingly, female benthics no longer based their choice on size; however, limnetic females continued to prefer more limnetic-shaped males. We show that shape is a magic trait, as it is the basis for both divergent adaptation and for assortative mating between species.  Next, I switch to male competition. Rugged fitness landscapes are thought to promote speciation, as they provide multiple adaptive peaks for populations to occupy. They have been little used in sexual selection research, however. We characterized the fitness landscape generated by sexual selection through male competition. We capitalized on the highly variable genotypic/phenotypic combinations found in an F2 mapping population, which has trait combinations not found in nature allowing us to experimentally tease apart selection on multiple traits. We then measured male competition in naturalized habitats corresponding to the native mating habitat of limnetic sticklebacks, assessing male ability to acquire territories and defend nests. We found correlational selection; more brightly colored, more aggressive males were more likely to establish territories. Surprisingly, other traits did not matter, including traits commonly assumed to influence male competitive ability, such as body size. Taken together, these results suggest the sexual selection is a key driver of speciation in stickleback fish.


Presentado por: Dra. Marta Barluenga.

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