S6-6 Friday, Jan. 5 11:00 - 11:30 Phylogeny and diversification: levels of glucocorticoid hormones and speciation rate in birds GARAMSZEGI, LZ*; HORMONEBASE CONSORTIUM, ; Estación Biológica de Doñana-CSIC; www.hormonebase.org email@example.com
Stress physiology may have consequences for species richness at macroevolutionary scales, because species that inhabit stressful environments would be favored to occupy and quickly adapt to new -and less stressful- habitats promoting species diversification. Furthermore, species that maintain broad within-species variation in stress response are more likely to have individuals that can successfully cope with unpredictable environmental challenges bringing them into new ecological niches than species with narrow within-species variation. We have tested these ideas relying on the HormoneBase repository, and investigated the relationship between baseline and stress-induced corticosterone levels and speciation rate in a phylogenetic study of birds. To estimate speciation rates, we applied Bayesian analysis of macroevolutionary mixtures that can account for variation in diversification rate among clades and through time. There was no evidence for either the mean of baseline or that of the stress-induced hormone levels being associated with the degree of speciation. The same observation was also held for the intra-specific variance of the traits and also when controlling for potentially confounding effects such as body mass or latitude. These results may imply that stress physiology plays a minor role in determining speciation rates in birds, because, for example, species in more- or less stressful environments are equally well-adapted and have equal probability of speciating.