Evolution of cryptic coloration in ectoparasites.

Cryptic coloration is a classic example of evolution by natural selection. However, it has been studied almost exclusively in predator-prey systems, despite the fact that it may evolve in other groups, such as ectoparasites. The principle defense of hosts against ectoparasites is grooming behavior, which has a visual component. Host-imposed selection should lead to the evolution of background matching if it helps ectoparasites escape from grooming. Here we use sister taxa comparisons to show that avian feather lice (Phthiraptera: Ischnocera) have evolved coloration that matches the host's plumage, except in the case of head lice, which are protected from grooming. We also show covariation of parasite and host color within a single species of louse. Thus, cryptic coloration has evolved both within and between species of feather lice. Other examples of the evolution of crypsis presumably exist among the 70,000 known species of ectoparasites that collectively represent five animal phyla.

Phylogenetic analysis of nuclear and mitochondrial genes supports species groups for Columbicola (Insecta: Phthiraptera).

The dove louse genus Columbicola has become a model system for studying the interface between microevolutionary processes and macroevolutionary patterns. This genus of parasitic louse (Phthiraptera) contains 80 described species placed into 24 species groups. Samples of Columbicola representing 49 species from 78 species of hosts were obtained and sequenced for mitochondrial (COI and 12S) and nuclear (EF-1alpha) genes. We included multiple representatives from most host species for a total of 154 individual Columbicola, the largest molecular phylogenetic study of a genus of parasitic louse to date. These sequences revealed considerable divergence within several widespread species of lice, and in some cases these species were paraphyletic. These divergences correlated with host association, indicating the potential for cryptic species in several of these widespread louse species. Both parsimony and Bayesian maximum likelihood phylogenetic analyses of these sequences support monophyly for nearly all the non-monotypic species groups included in this study. These trees also revealed considerable structure with respect to biogeographic region and host clade association. These patterns indicated that switching of parasites between host clades is limited by biogeographic proximity.