The Journal of Heredity 2002:93(6)
© 2002 The American Genetic Association 93:432-438
Brief Communication |
Disparity in Population Differentiation of Sex-Linked and Autosomal Variation in Sibling Species of the Jaera albifrons (Isopoda) Complex
From the Department of Evolutionary Biology, University of Copenhagen, Universitetsparken 15, DK-2100 Copenhagen Ø, Denmark.
Address correspondence to Hans R. Siegismund at the address above, or e-mail: HSiegismund{at}ZI.KU.DK.
The genetic variation at four enzyme loci is described for 22 populations of three Jaera species—J. albifrons, J. ischiosetosa, and J. praehirsuta—in the J. albifrons complex (Crustacea, Isopoda) in Denmark. The variation at three of the loci is similar, with the allele frequency spectra close to each other in all three species. An evolutionary tree based on the variation at these three loci revealed that the populations from the different species are completely intermixed in the tree. This was supported by hierarchical F-statistics where the between-species component was zero. At a fourth locus, Gpi (glucose phosphate isomerase), the species differ substantially. This locus is sex linked in J. ischiosetosa, but in the two other species, J. albifrons and J. praehirsuta, it is either found on autosomes or is sex linked with a high recombination rate between the locus and the centromere. An evolutionary tree for this locus partitions the populations into separate groups and a hierarchical F-statistic has a between-species component of about 50%. The results are attributed to introgression with a higher rate for autosomes than for sex chromosomes.