The genetic architecture of local adaptation in a dioecious species: implications for chromosome evolution

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This study will provide a deeper understanding into how natural selection leads to the divergence of populations, the first step toward speciation, focusing on traits that differ between males and females. The results of this study will address fundamental aspects of how selection varies on males and females and how this affects the structure of genes and chromosomes. Understanding these processes will broaden our knowledge about a central question of biology: Why are there so many different kinds of organisms? The work will train several undergraduate and graduate students, as well as a postdoctoral scholar, in both scientific research and public outreach, and provide them with opportunities to establish international collaborations. The researchers will work with scientists at Bloomington, IN, WonderLab Museum of Science, Health and Technology and with teachers at the Templeton Elementary School to create public displays about pollination biology and plant reproduction. This study will investigate the genetic architecture of local adaptation using the short-lived, herbaceous, dioecious, perennial plant white campion (Silene latifolia). The researchers hypothesize that local adaptation occurs primarily via selection on males, leading not only to phenotypic differences between males and females, but also the genetic basis of local adaptation being associated with pseudoautosomal loci. To test this hypothesis, they will conduct a multi-year reciprocal-transplant experiment using two populations from Spain and Croatia that are highly divergent for sexually dimorphic traits. They will also conduct manipulative experiments in the greenhouse and the field to determine: (1) which traits are involved in local adaptation (via phenotypic-selection analyses), and how variation in water availability and air temperature influences this adaptation (via water and temperature manipulation), (2) whether males are under greater selection to diverge, and (3) whether sexual antagonism exists for any of these traits. In addition to pure-population individuals, F2 progeny planted in both Spain and Croatia will allow further determination of which traits and quantitative trait loci (QTL) are targets of differential selection between the two habitats. They will measure the extent to which QTL for divergent traits are essentially sex specific in their effect or shared between the sexes, and lastly, whether QTL responsible for adaptive trait divergence occur in the pseudoautosomal region of the sex chromosomes. The result will determine which traits of males and females are under selection, the extent to which antagonistic selection between males and females is implicated in adaptive population differentiation, and the extent to which these loci are located on the X and Y chromosomes.