ABSTRACT
There is little doubt that biological extinctions are strongly associated with human contact, as paleoecology links periods of widespread animal extinctions with human colonization (Burney and Flannery 2006). Much effort has addressed the relative impacts of drivers of extinction, including attempts to measure the consequences of invasive species: (1) invasive predation; (2) invasive competition; (3) invasive habitat alteration; and (4) invasive pathogens (IUCN 2001). Clavero et al. (2009) show that these categories are more strongly associated with extinction risks than other drivers. However, distinguishing their individual effects is challenging. For example, introduction of mammals is strongly associated with avian extinctions on oceanic islands (Blackburn et al. 2004), but analyses including other parameters show that intrinsic island factors (e.g. size and isolation) have an even stronger association with avian extinction risk (Karels et al. 2007). Assessments of impacts of disease alone have lagged behind. However, increasing awareness of emerging infectious diseases (Daszak et al. 2000) has led to recognition of the impact of pathogens in populations with limited or no previous exposure and thus high susceptibility (Smith et al. 2006, 2009). These studies point to the urgent need to understand the identity, abundance, and impact of pathogens in wildlife populations, especially in populations that are perpetually small, such as those on remote islands.
