Host phylogeography and beta diversity in avian haemosporidian (Plasmodiidae) assemblages of the Lesser Antilles.

1. We estimated the correlation between host phylogeographical structure and beta diversity of avian haemosporidian assemblages of passerine birds to determine the degree to which parasite communities change with host evolution, expressed as genetic divergence between island populations, and we investigated whether differences among islands in the haemosporidia of a particular host species reflect beta diversity in the entire parasite assemblage, beta diversity in vectors, turnover of bird species and/or geographical distance. 2. We used Mantel tests to assess the significance of partial correlations between host nucleotide difference (based on cytochrome b) and haemosporidian (Haemoproteus spp. and Plasmodium spp.) mitochondrial lineage beta diversity within a given host species and between Plasmodium mitochondrial lineage beta diversity and mosquito and bird species beta diversity (or turnover). Three abundant and widespread host species (Tiaris bicolor, Coereba flaveola and Loxigilla noctis/barbadensis) were included in the study. Haemosporidian lineage beta diversity among nine islands was assessed using the Chao-Jaccard, Chao-Sørensen and Morisita-Horn indices of community similarity. Beta diversity indices of mosquito species and turnover of bird species were calculated from data in published records and field guides. 3. In Loxigilla spp., we found a positive correlation with geographical distance and an unexpected negative correlation between haemosporidian beta diversity and host genetic distance. Tiaris bicolor exhibited a significant positive correlation between haemosporidian beta diversity and beta diversity within the entire parasite assemblage. We did not find significant correlations between parasite beta diversity and mosquito beta diversity or bird species turnover. 4. Host phylogeographical structure does not appear to drive within-host beta diversity of haemosporidian lineages. Instead, the array of parasites on one host can reflect the haemosporidian assemblage on other hosts.