Laboratory of Entomology, Wageningen University, PO Box 8031, 6700 EH Wageningen, The Netherlands.
J Insect Sci. 2009;9:1-8. doi: 10.1673/031.009.6901.
The flea beetle Phyllotreta nemorum L. (Coleoptera: Chrysomelidae) is genetically polymorphic for resistance against the defences of one of its host plants, Barbarea vulgaris R.Br. (Brassicales: Brassicaceae). Whereas resistant flea beetles are able to use B. vulgaris as well as other cruciferous plants as food, non-resistant beetles cannot survive on B. vulgaris. This limitation to host plant use of non-resistant beetles could potentially lead to asymmetric gene flow and some degree of genetic isolation between the different resistance-genotypes. Therefore, we studied the extent of genetic differentiation at neutral allozyme loci between samples of flea beetles that were collected at different locations and first tested for resistance phenotype. Since earlier work has shown a weak, but significant, effect of geographical distance between the samples on their genetic differentiation, in the present study variation at the neutral allozyme loci in P. nemorum was partitioned between geographical distance and resistance-phenotype. Both sources independently contributed statistically significantly to population differentiation. Thus, there appears to be a limitation to genetic exchange between the resistant and non-resistant flea beetles when corrections are made for their geographic differentiation. This is consistent with the presence of some degree of host race formation in this flea beetle.
豌豆叶甲 Phyllotreta nemorum L.（鞘翅目：叶甲科）在其寄主植物之一的 Barbarea vulgaris R.Br.（十字花科：芸薹属）防御机制方面具有遗传多态性。虽然抗性豌豆叶甲能够将 B. vulgaris 以及其他十字花科植物用作食物，但非抗性叶甲则无法在 B. vulgaris 上生存。这种非抗性叶甲对寄主植物的使用限制可能导致不同抗性基因型之间的不对称基因流和一定程度的遗传隔离。因此，我们研究了在不同地点采集的豌豆叶甲样本在中性等位酶基因座上的遗传分化程度，并首先对其抗性表型进行了测试。由于早期的研究表明，样本之间的地理距离对其遗传分化有微弱但显著的影响，因此在本研究中，P. nemorum 中性等位酶基因座的变异在地理距离和抗性表型之间进行了划分。这两个来源都独立地对种群分化做出了统计学上的显著贡献。因此，在对其地理分化进行校正后，抗性和非抗性豌豆叶甲之间的遗传交换似乎受到限制。这与这种豌豆叶甲存在一定程度的寄主种族形成是一致的。
