Meeting Abstract

7.5  Sunday, Jan. 4  Epidemic disease homogenizes amphibian communities SMITH, Kevin G.*; LIPS, Karen R.; CHASE, Jonathan M.; Washington Univ. in St. Louis; Southern Illinois Univ., Carbondale; Washington Univ. in St. Louis kgs@wustl.edu

The modern biodiversity crisis is characterized by an unprecedented loss of species, owing to threats such as habitat loss, global change, and emerging pathogens. If these threats cause local extinctions nonrandomly across communities, then among-community biotic distinctiveness, or beta diversity, will be lost. This underappreciated loss of diversity, known as biotic homogenization, can rob ecosystems of important functions and disproportionately affect regional diversity such that regional extinctions outnumber local extirpations. Here, we show that a pathogenic agent of global amphibian decline, Batrachochytrium dendrobatidis (Bd), homogenizes diverse tropical American amphibian communities by causing nonrandom extinctions resulting in a dramatic loss of beta diversity. Prior to the appearance of Bd, amphibian communities had high beta diversity owing to the presence of many endemic species, and thus were less similar than would be expected by chance. Following invasion by Bd, the nonrandom loss of endemic species resulted in significantly reduced beta diversity, such that amphibian communities became more similar than expected if loss of species were random. Furthermore, post-decline community similarity was no longer structured by geographic distance, indicating that presence of Bd now drives patterns of amphibian biodiversity and overrides historical biogeographic determinants of community composition and diversity. Our results suggest that threats such as Bd can act as powerful ecological filters at the local scale, reducing biodiversity to homogenized relict assemblages of threat-tolerant species and causing concomitant biodiversity loss at regional and global scales.