Meeting Abstract

141.2  Monday, Jan. 7  Kidney mass of passerine birds in relation to diet, habitat, and phylogeny SHIRKEY, NJ*; GARLAND JR., T; Univ. of California, Riverside; Univ. of California, Riverside nshir001@ucr.edu

The kidney plays an important role in electrolyte homeostasis, acid-base balance, osmoregulation, water conservation, and waste removal (in particular nitrogenous waste). Diversity in such factors as diet (e.g., protein content) and habitat (e.g., water availability) may cause variation in the selective regime and, ultimately, lead to evolutionary changes in kidney size and/or structure. A previous interspecific comparative study (Barcelo et al. 2012) found no relationship between kidney mass (corrected for body mass) and the % invertebrates in the diet of passerine birds, but suffered from a relatively small sample size (n=16). In this study, data for kidney and body mass were collected for 100 species of passerine birds, along with corresponding diet and habitat data. Conventional and phylogenetically informed (multiple) regressions were performed with log kidney mass as the dependent variable, log body mass as a covariate, and all possible combinations of diet (% invertebrates in 5 categories, treated as a continuous variable), habitat (categorical: aquatic, mesic, semi-xeric, xeric), and clade (categorical: 6 superfamilies). Phylogenetic signal (Blomberg et al. 2003) in relative kidney mass was statistically non-significant, and conventional statistical methods consistently produced the best-fitting models. Diet was included as a variable in all top-performing models, and greater dietary consumption of invertebrates was a significant positive predictor of kidney mass. Neither habitat nor clade was a significant predictor of kidney mass. Our results suggest that the amount of dietary nitrogen consumed may be one factor that led to diversification of kidney size (and possibly structure) in passerine birds.