PDF(Pubmed)
Abstract：
Organisms that have repeatedly evolved similar morphologies owing to the same selective pressures provide excellent cases in which to examine specific morphological changes and their relevance to the ecology and evolution of taxa. Hosts of permanent parasites act as an independent evolutionary experiment, as parasites on these hosts are thought to be undergoing similar selective pressures. Parasitic feather lice have repeatedly diversified into convergent ecomorphs in different microhabitats on their avian hosts. We quantified specific morphological characters to determine (i) which traits are associated with each ecomorph, (ii) the quantitative differences between these ecomorphs, and (iii) if there is evidence of displacement among co-occurring lice as might be expected under louse-louse competition on the host. We used nano-computed tomography scan data of 89 specimens, belonging to four repeatedly evolved ecomorphs, to examine their mandibular muscle volume, limb length and three-dimensional head shape data. Here, we find evidence that lice repeatedly evolve similar morphologies as a mechanism to escape host defences, but also diverge into different ecomorphs related to the way they escape these defences. Lice that co-occur with other genera on a host exhibit greater morphological divergence, indicating a potential role of competition in evolutionary divergence.
摘要：
由于相同的选择压力而反复进化出相似形态的生物提供了极好的案例，可以检查特定的形态变化及其与分类群的生态学和进化的相关性。永久寄生虫的宿主作为一个独立的进化实验，因为这些宿主上的寄生虫被认为正在经历类似的选择压力。寄生羽毛虱子在其鸟类寄主的不同微生境中反复分化为会聚的生态形态。我们量化了特定的形态特征，以确定（i）哪些性状与每个生态形态相关，(二)这些形态之间的数量差异，和（iii）如果有证据表明在宿主的虱子竞争下可以预期的同时发生的虱子之间的位移。我们使用了89个标本的纳米计算机断层扫描数据，属于四个反复进化的生态型，检查他们的下颌肌肉体积，肢体长度和三维头部形状数据。这里,我们发现有证据表明，虱子反复进化出相似的形态作为逃避宿主防御的机制，但也会分化为与他们逃离这些防御的方式有关的不同生态。与宿主上其他属共同出现的虱子表现出更大的形态差异，表明竞争在进化分歧中的潜在作用。
