Originally published as Genetics Published Articles Ahead of Print on April 15, 2007.

Genetics, Vol. 176, 1209-1222, June 2007, Copyright © 2007
doi:10.1534/genetics.106.064949

Genetic Architecture of Conspecific Sperm Precedence in Allonemobius fasciatus and A. socius

Seth C. Britch*,1, Emma J. Swartout*, Daniel D. Hampton{dagger}, Michael L. Draney{ddagger}, Jiming Chu§, Jeremy L. Marshall** and Daniel J. Howard*

* Department of Biology, New Mexico State University, Las Cruces, New Mexico 88003, {dagger} Duke University School of Medicine, Durham, North Carolina 27706, {ddagger} Department of Natural and Applied Sciences, University of Wisconsin, Green Bay, Wisconsin 54311, § Health Occupations Program, Dona Ana Branch Community College, Las Cruces, New Mexico 88003 and ** Department of Entomology, Kansas State University, Manhattan, Kansas 66506

1 Corresponding author: USDA-ARS, Center for Medical, Agricultural, and Veterinary Entomology, 1600/1700 SW 23rd Dr., Gainesville, FL 32608.
E-mail: seth.britch{at}ars.usda.gov

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 postinsemination prezygotic reproductive barrier. With amplified fragment-length polymorphism (AFLP) markers and controlled crosses we constructed linkage maps and estimated positions of QTL associated with CSP. The majority of QTL have low to moderate effects, although a few QTL exist in A. socius with large effects, and the numbers of QTL are comparable to numbers of genes accounting for species differences in other studies. The QTL are spread across many unlinked markers, yet QTL placed with linked markers are on a small number of linkage groups that 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.