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BMC Biol. 2012; 10: 52.
Published online Jun 20, 2012. doi:  10.1186/1741-7007-10-52
PMCID: PMC3391173
Repeated adaptive divergence of microhabitat specialization in avian feather lice
Kevin P Johnson,corresponding author1 Scott M Shreve,2 and Vincent S Smith3
1Illinois Natural History Survey, University of Illinois, Champaign, IL, USA
2Department of Entomology, University of Illinois, Urbana, IL, USA
3The Natural History Museum, London, UK
corresponding authorCorresponding author.
Kevin P Johnson: kpjohnso/at/illinois.edu; Scott M Shreve: smshreve/at/illinois.edu; Vincent S Smith: vince/at/vsmith.info
Received March 20, 2012; Accepted June 20, 2012.
Abstract
Background
Repeated adaptive radiations are evident when phenotypic divergence occurs within lineages, but this divergence into different forms is convergent when compared across lineages. Classic examples of such repeated adaptive divergence occur in island (for example, Caribbean Anolis lizards) and lake systems (for example, African cichlids). Host-parasite systems in many respects are analogous to island systems, where host species represent isolated islands for parasites whose life cycle is highly tied to that of their hosts. Thus, host-parasite systems might exhibit interesting cases of repeated adaptive divergence as seen in island and lake systems.
The feather lice of birds spend their entire life cycle on the body of the host and occupy distinct microhabitats on the host: head, wing, body and generalist. These microhabitat specialists show pronounced morphological differences corresponding to how they escape from host preening. We tested whether these different microhabitat specialists were a case of repeated adaptive divergence by constructing both morphological and molecular phylogenies for a diversity of avian feather lice, including many examples of head, wing, body and generalist forms.
Results
Morphological and molecular based phylogenies were highly incongruent, which could be explained by rampant convergence in morphology related to microhabitat specialization on the host. In many cases lice from different microhabitat specializations, but from the same group of birds, were sister taxa.
Conclusions
This pattern indicates a process of repeated adaptive divergence of these parasites within host group, but convergence when comparing parasites across host groups. These results suggest that host-parasite systems might be another case in which repeated adaptive radiations could be relatively common, but potentially overlooked, because morphological convergence can obscure evolutionary relationships.
Keywords: adaptive radiation, convergence, Phthiraptera, ectoparasites, phylogenetics
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