PLYfiles_LouseEcomorphs zip files with 3D .ply files of louse specimens. (over 800MB) from Parasite escape mechanisms drive morphological diversification in avian lice

Organisms that have repeatedly evolved similar morphologies due 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 defenses, but also diverge into different ecomorphs related to the way they escape these defenses. Lice that co-occur with other genera on a host exhibit greater morphological divergence, indicating a potential role of competition in evolutionary divergence.

因相同选择压力反复演化出相似形态的生物，为探究特定形态变化及其与类群生态学和演化的关联提供了绝佳研究案例。永久性寄生虫的宿主本身即为一项独立的演化实验，因为寄生于此类宿主的寄生虫被认为正承受相似的选择压力。寄生羽虱在其鸟类宿主的不同微生境中，反复分化出趋同生态形态。我们通过量化特定形态特征，旨在达成三项研究目标：(1) 明确与各类生态形态相对应的性状；(2) 解析不同生态形态间的量化差异；(3) 检验是否存在共栖羽虱间的生态位置换证据——这一结果符合宿主体表羽虱间竞争的理论预期。我们借助隶属于4种反复演化出的生态形态类群的89份标本的纳米计算机断层扫描（nano-computed tomography）数据，分析了其下颌肌肉体积、附肢长度以及头部三维形态数据。本研究发现，羽虱会通过反复演化出相似形态以规避宿主的防御机制，同时也会依据各自的防御规避策略分化为不同的生态形态。在同一宿主上与其他羽虱属共栖的类群，其形态分化程度更高，这表明竞争在羽虱的演化分化中可能发挥了关键作用。