Siegismund H R
Department of Evolutionary Biology, University of Copenhagen, Universitetsparken 15, DK-2100 Copenhagen Ø, Denmark.
J Hered. 2002 Nov-Dec;93(6):432-9. doi: 10.1093/jhered/93.6.432.
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.
描述了丹麦白额耶尔蟹（Jaera albifrons）复合体（甲壳纲，等足目）中三种耶尔蟹——白额耶尔蟹（J. albifrons）、坐骨刚毛耶尔蟹（J. ischiosetosa）和前毛耶尔蟹（J. praehirsuta）的22个种群在四个酶位点的遗传变异。其中三个位点的变异相似，在所有三个物种中，等位基因频率谱彼此接近。基于这三个位点变异构建的进化树显示，来自不同物种的种群在树中完全混合在一起。分层F统计量支持了这一点，其中物种间成分等于零。在第四个位点，即磷酸葡萄糖异构酶（Gpi）位点，物种间存在显著差异。该位点在坐骨刚毛耶尔蟹中与性别相关联，但在其他两个物种，即白额耶尔蟹和前毛耶尔蟹中，它要么位于常染色体上，要么与性别相关联，且该位点与着丝粒之间的重组率很高。该位点的进化树将种群划分为不同的组，分层F统计量的物种间成分约为50%。结果归因于基因渐渗，常染色体的基因渐渗率高于性染色体。
