Parasite escape mechanisms drive morphological diversification in avian lice

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.

Rapid Targeted Assembly of the Proteome Reveals Evolutionary Variation of GC Content in Avian Lice

“…Feather lice genera have been grouped into different ecomorphs based on similar morphological characteristics. These specialized phenotypes allow them to live in different areas of their avian host’s body to escape host defense mechanisms 24 , 87 - 89 and found evidence of convergent evolution in these ecomorphs but it is unknown if each ecomorph type experiences the same selective pressures on the same genes or expresses similar genetic pathways. Signatures of convergent evolution have been found in other species that exhibit ecomorphs, which can tell us more about the genetic architecture of closely and distantly related organisms and the role selective pressures play in diversification.…”