GALAPAGOS · Cophylogeography of ecological replicates: the coevolution and biogeography of Galapagos mockingbirds and their ectoparasites

Cophylogeography of ecological replicates: the coevolution and biogeography of Galapagos mockingbirds and their ectoparasites

Data necessary to fulfil proposed tasks were generated using a specimen collection obtained from collaborators from the Zurich University (Dr P. Hoeck and Dr L. Keller). The collection of 2000+ specimens of parasites was sorted and parasite taxa identified. Three most commonly represented species were selected for a subsequent genetic study. The species comprised lice from two different suborders (Amblycera: Myrsidea nesomimi and Ischnocera: Brueelia galapagensis) and a yet to be taxonomically described Astigmatid mite (Analges sp). Two genes (COI, EF1a) were sequenced for a total of 247 parasite specimens. In addition to the genetic data obtained for the parasites 107 mockingbird specimens were sequenced for the COI gene and a population genetic data set (microsatellite allelic variability) provided by a collaborator (P. Hoeck) was analysed by us for 400 mockingbird specimens. Genetic data were analysed using up-to-date methods of phylogenetics and population genetics. A novel approach of reconciling phylogenetic histories for parasite and host taxa was implemented using genealogy-reconstruction software (program BEAST). Results of these analyses provided key insights into the course of evolution of the host-parasite association across the Galapagos archipelago. These data are directly beneficial to conservation biologists at the Galapagos National Park, as part of a reintroduction program for the endangered Floreana mockingbird. The most significant findings included: 1. All studied species showed an explicit pattern of geography-dependent structure forming genetic lineages specific for particular islands of the archipelago. 2. Despite clearly discernible co-evolutionary history shared between the mockingbird hosts and their parasites, occasional incongruences between some phylogenies were observed. These represent random population processes following colonization of newly emerged islands. 3. The levels of genetic diversity of populations differed between the three species of parasites. Low levels of variability were seen in Brueelia, whereas deeper genetic distances were seen in Myrsidea and Analges. These differences were attributed to differences in ecological characters of the parasites (differences in feeding habits, parasite mobility and life strategies). 4. A link between the genetic sizes of the populations of parasites, the geographic area of the islands and the genetic size of the host populations was found. This shows that some ecological factors like habitat size affect all organisms involved in the ecological association (host as well as its parasites) and that the parasites may be used as a resource to extract biologically relevant information about their hosts. The studied system provides a model for understanding evolutionary forces affecting the genetic character of host-parasite populations colonising new habitats. These results will be of significant interest to a wide spectrum of evolutionary biologists, ecologists, zoologists and conservation biologists. The results also contain a potential to help creating measures towards planned reintroduction of the critically endangered Floreana mockingbird (Floreana Mockingbird Reintroduction Program organised by the Charles Darwin Foundation, please see http://www.darwinfoundation.org online).

Data: CORDIS, © European Union