One of the strengths of our lab – compared to many labs that work on host-parasite coevolution – is that we have a thorough understanding of the systematics of both the host and parasite groups we work on.  Over the years, members of the Clayton lab have published many papers on the systematics of birds and lice.  Our publications include work on taxonomy, phylogenetic reconstruction, and comparisons of host and parasite phylogenies to assess the extent of host-parasite cospeciation in particular groups.  We sometimes also publish papers, in collaboration with colleagues, on the systematics of other groups, such as parasitic flies of bats (Streblidae).

Our PEET Project Web Site
PIPeR (Price Institute for Phthirapteran Research)
New taxa of lice described by D.H. Clayton

Unlocking the Black Box of Feather Louse Diversity:
a revision of the hyper-diverse genus Brueelia

Project in collaboration with Kevin Johnson.

Lice are wingless, obligate ectoparasites of birds and mammals.  Since they pass their entire life cycle on the body of the host, lice are unusually tractable organisms for research in population biology.  Their close association with the host has resulted in pronounced host specificity and cospeciation in some groups.  Indeed, lice are one of the most common model systems used in the development of analytical methods for assessing patterns and rates of cospeciation.  Their tractability in ecological time, combined with a history of cospeciation, also makes them one of the best groups for research on ecological factors governing the process of speciation, in general. Unfortunately, the role of lice as models for broad-based research continues to be hampered by the miserable state of louse systematics.  The host specificity of many genera has been exaggerated by the circular reasoning common among earlier taxonomists, who often described new species on the basis of host associations, rather than on the basis of the lice themselves.

One genus desperately in need of revision is the hyper-diverse genus Brueelia.  There are over 280 known species of Brueelia, most of which parasitize songbirds (Passeriformes).  Intriguingly, species of Brueelia appear to be highly host specific, yet preliminary phylogenetic data for Brueelia show a lack of congruence with the host phylogeny.  In short, Brueelia represents the extreme opposite end of the spectrum from the classic case of near perfect cospeciation – chewing lice (Geomydoecus) on pocket gophers.  Revisionary work is needed to determine whether the lack of congruence is a consequence of real biological phenomena, such as host switching caused by the phoretic dispersal of lice on hippoboscid flies (which is common in Brueelia) or whether it is an artifact of taxonomic over-splitting. 

In this project, we are using morphological and molecular approaches to provide species descriptions and revisionary taxonomy for the genus Brueelia.  We are reconstructing the evolutionary history of Brueelia using morphological characters (~150) and molecular data (mitochondrial genes: COI and 12S rDNA, and nuclear genes: wingless and EF-1alpha).  When robust phylogenies are in hand, we will compare the louse phylogeny to existing host trees to investigate the relative importance of co-speciation, host-switching, and host biogeography in the evolution of this hyper-diverse genus.

Chewing Lice on Songbirds in Nordic Countries

The species composition and distribution of chewing lice in the Nordic countries are generally poorly, and the potential to discover new species and new host-parasite associations is high. This is especially true for lice of passerines (songbirds), where, potentially, less than 10% of the species and host records are known. We are actively collecting lice from a wide range of host species (including non-passerines where possible) is predicted to substantially increase the number of know chewing louse species in the Nordic countries, primarily Sweden. These will be added to a larger, international, collection, with the aim to establish proper generic limits of several louse complexes (e.g., Brueelia see above project, and Philopterus). In addition, this project will ultimately provide identification keys, photographs, illustrations and detailed descriptions of all collected species that will be made available to researchers world-wide.

This project is spearheaded by postdoctoral fellow Daniel "Leo" Gustafsson. 

Gustaafsson in Sweden     

Daniel "Leo" Gustafsson holding a Goldcrest (kinglet: Regulus regulus) with bird-bander Juho, who is holding a Mute Swan (Cygnus olor) at a field site in Sweden.

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