Competition theory predicts that communities at small spatial scales should consist of species more dissimilar than expected by chance. We find a strikingly different pattern in a multi-continent dataset (55 presence-absence matrices from 24 locations) on the composition of mixed-species bird flocks, important subunits of local bird communities the world over. Using null models and randomization tests followed by meta-analysis, we find the association strength of species in flocks to be strongly related to similarity...

Theory predicts that sexual reproduction provides evolutionary advantages over asexual reproduction by reducing mutational load and increasing adaptive potential. Here, we test the latter prediction in the context of plant defences against pathogens because pathogens frequently reduce plant fitness and drive the evolution of plant defences. Specifically, we ask whether sexual evening primrose plant lineages (Onagraceae) have faster rates of adaptive molecular evolution and altered gene expression of a class I chitinase, a gene implicated...