Genetic Architecture of Conspecificc Sperm Precedence in Allonemobius Fasciatus and Allonemobious Socius

The evolution of barriers to gene exchange is centrally important to speciation. We used the crickets Allonemobius fasciatus and A. socius to investigate the genetic architecture of conspecific sperm precedence (CSP), a post-insemination prezygotic reproductive barrier. With AFLP markers and controlled crosses we constructed linkage maps and estimated positions of QTL associated with CSP. The majority of QTLs have low to moderate effects, although a few QTLs exist in A. socius with large effects, and the numbers of QTLs are comparable to numbers of genes accounting for species differences in other studies. The QTLs are spread across many unlinked markers, yet QTLs placed with linked markers are on a small number of linkage groups which could reflect the role of the large Allonemobius sex chromosome in prezygotic isolation. Although many QTL had positive effects on conspecific sperm utilization several QTL also exerted negative effects, which could be explained by intraspecific sexual conflict, sperm competition, or epistasis of introgressed genes on novel backgrounds. One unexpected outcome was that A. socius CSP alleles have a stronger effect than those from A. fasciatus in hybrid females, causing hybrids to behave like A. socius with regard to sperm utilization. Implications of this asymmetry in the Allonemobius hybrid zone are discussed.

Key Words: QTL, biomodal hybrid zone, conspecific sperm precedence, reproductive isolation, speciation

Online ISS 1091-6490
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