Transient microgeographic clines during B chromosome invasion

Camacho, J. P. M., Shaw, M., Cabrero, J., Bakkali, M., Ruíz-Estévez, M., Ruíz-Ruano, F. J., Martín-Blázquez,, R. and López-León, M. D. (2015) Transient microgeographic clines during B chromosome invasion. The American Naturalist, 186 (5). pp. 675-681. ISSN 0003-0147 doi: 10.1086/683172

Abstract/Summary

The near-neutral model of B chromosome evolution predicts that the invasion of a new population should last some tens of generations, but the details on how it proceeds in real populations are mostly unknown. Trying to fill this gap, we analyze here a natural population of the grasshopper Eyprepocnemis plorans at three time points during the last 35 years. Our results show that B chromosome frequency increased significantly during this period, and that a cline observed in 1992 had disappeared in 2012 once B frequency reached an upper limit in all sites sampled. This indicates that, during B chromosome invasion, at microgeographic scale, transient clines for B frequency are formed at the invasion front. Computer simulation experiments showed that the pattern of change observed for genotypic frequencies is consistent with the existence of B chromosome drive through females and selection against individuals with high number of B chromosomes.