Observed - expected functional-phylogenetic host specificity reveals phylogenetic and ecological host-specialist parasites
Host specificity of avian malaria parasites. (a) Differentials between observed and expected host functional–phylogenetic specificity (STD*) at varying a weights. Weights approaching 0 give higher weight to host ecological distance; values approaching 1 give higher weight to host phylogenetic distance. Negative differentials indicate clustered hosts (more similar than expected); positive values indicate overdispersed hosts (more dissimilar than expected). Differentials were generated from 10 000 iterations, using randomly sampled host phylogenies and habitat dendrograms in each iteration. Boxplots show differential medians (lines within boxes),
and 25% and 75% quartiles (hinges) for individual parasites. Asterisks (*) indicate significant differences from 0. (b) Relationship between a weights and specificity indices for select parasites infecting ≥3 host species. For clarity, four parasites were chosen to showcase the range of index patterns observed, with colours matching corresponding boxplots in part (a). Indices were generated using only nearest taxon functional–phylogenetic distance (NTSTD*; top graph) or mean pairwise distances (STD*). Higher indices indicate more generalist parasites, while low scores indicate specialists.