Meeting Abstract

30.3  Sunday, Jan. 5 09:00  The biogeography of endocrinology MOORE, I T; Virginia Tech itmoore@vt.edu

Natural historians have long known of the latitudinal variation in clutch size with tropical vertebrates laying fewer eggs and having smaller litters than higher latitude species. More recently, physiologists have described latitudinal variation in a variety of processes that suggest tropical species exhibit a slower pace of life than higher latitude species. Fortunately, enough environmental endocrinology studies have been performed that we can now look for broader endocrine patterns across species and habitats in a similar way that natural historians have investigated biogeographical patterns. Such patterns could serve to elucidate the how selection favors certain endocrine phenotypes. One prominent example has been the description of a positive relationship between testosterone and latitude in birds with tropical species typically having lower levels than higher latitude species. Similarly, a positive relationship between corticosterone and latitude has also been described in birds. In amphibians, testosterone and corticosterone are both positively related to latitude. Further, for both amphibians and reptiles, testosterone levels are negatively related to breeding season length. Thus, it appears that similar relationships between the hormones and geography do exist in a variety of taxa, suggesting that environmental factors may be a stronger determinant of hormone levels. As environmental factors also determine life history characteristics, it is likely that selection favoring certain life history traits also favors particular hormonal mechanisms and this is why we see relationships between geography, natural history, and endocrine mechanisms.