Dhuyvetter Hilde, Maelfait Jean-Pierre, Desender Konjev
Entomology Department, Royal Belgian Institute of Natural Sciences, Vautierstreet 29, Brussels, Belgium.
Saline Syst. 2007 Apr 24;3:4. doi: 10.1186/1746-1448-3-4.
Pogonus littoralis and Pogonus chalceus are very close related species with quite different ecological preferences within salt marshes. We study the evolutionary processes in and between these presumably young species. Therefore, we compare the variation in ecologically relevant characters and the genetic variation within one of the species (intraspecific differentiation) with the variation of the two types of characters between the two species (interspecific variation). Data are compared between two independent sets of populations, one set at a small geographical scale (the ecologically diverse Guérande area in France) and the other set at a Atlantic-Mediterranean scale.
Body and relative wing size and IDH1 allozyme data show that the intraspecific variation in P. chalceus is high and in the same range as the interspecific variation (P. chalceus versus P. littoralis). Based on neutral markers (other allozymes and mitochondrial DNA) on the other hand, the intraspecific variation in P. chalceus is much lower in comparison to the interspecific variation.
The different ecotypes in the highly polytypic species P. chalceus are as highly differentiated in ecological characters as true species, but are not recognised as such by screening neutral DNA polymorphisms. This can be interpreted as a case of ongoing speciation driven by natural selection adapting each ecotype to its respective ecological niche. The same ecological process can be recognised in the differentiation between the two sister species, where en plus reproductive isolation between the two gene pools occurred, allowing independent drift and mutation accumulation in neutral genetic characters.
滨海鬃长足虻和铜鬃长足虻是亲缘关系非常近的物种，在盐沼中具有截然不同的生态偏好。我们研究这些可能的年轻物种内部以及它们之间的进化过程。因此，我们将一个物种内部与生态相关性状的变异以及遗传变异（种内分化）与两个物种之间这两种性状的变异（种间变异）进行比较。在两组独立的种群之间对数据进行比较，一组是在小地理尺度上（法国生态多样的盖朗德地区），另一组是在大西洋 - 地中海尺度上。
身体和相对翅大小以及异柠檬酸脱氢酶1同工酶数据表明，铜鬃长足虻的种内变异很高，且与种间变异（铜鬃长足虻与滨海鬃长足虻相比）处于同一范围。另一方面，基于中性标记（其他同工酶和线粒体DNA），铜鬃长足虻的种内变异与种间变异相比要低得多。
高度多型的铜鬃长足虻中的不同生态型在生态性状上的分化程度与真正的物种一样高，但通过筛选中性DNA多态性却未被识别为真正的物种。这可以解释为一个正在进行的物种形成案例，是由自然选择驱动的，使每个生态型适应其各自的生态位。在这两个姐妹物种之间的分化中也可以识别出相同的生态过程，其中两个基因库之间还发生了额外的生殖隔离，使得中性遗传性状能够独立漂变和积累突变。
