Constraints on correlated evolution of ecological specialization and body size in avian brood parasites.
Lajeunesse, Marc*,1, 1 Cornell University, Ithaca, NY, USA
ABSTRACT- Body size of parasites may be an adaptive component of specificity that can constrain ecological opportunity and use of potential host species. To test this hypothesis, I correlate body size with the number of known host species (e.g., host range) of 76 species of avian brood parasite (birds that defer parental care by laying eggs in nests of other bird species). I find that across the six major clades of brood parasitism (cowbirds, honeyguides and African finches, old and new world cuckoos, and parasitic fowl), species with marginal body sizes (at extremes of size ranges found across species) have narrower host ranges than brood parasites with more intermediate body sizes. This pattern was robust when using only wing length as a surrogate of body size across several species, when using multiple measurements of body size but on fewer species, and after accounting for a hypothesized evolutionary relationship between these brood parasites. I also found that phylogenetic changes in body size were also associated with changes in ecological specialization of brood parasites. These results indicate that selection towards marginal body sizes (either larger or smaller sizes) can be matched with a joint reduction to niche breadth.
Key words: avian brood parasites, host range, body size, comparative analysis
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