The complexity of amphibian population declines: understanding the role of cofactors in driving amphibian losses

Abstract

Population losses and extinctions of species are occurring at unprecedented rates, as exemplified by declines and extinctions of amphibians worldwide. However, studies of amphibian population declines generally do not address the complexity of the phenomenon or its implications for ecological communities, focusing instead on single factors affecting particular amphibian species. We argue that the causes for amphibian population declines are complex; may differ among species, populations, and life stages within a population; and are context dependent with multiple stressors interacting to drive declines. Because amphibians are key components of communities, we emphasize the importance of investigating amphibian declines at the community level. Selection pressures over evolutionary time have molded amphibian life history characteristics, such that they may remain static even in the face of strong, recent human-induced selection pressures.

Evolved pesticide tolerance influences susceptibility to parasites in amphibians

“…The influence of pesticides on host–parasite interactions has been explored in many systems (Blaustein et al., 2011; Dietrich, Van Gaest, Strickland, & Arkoosh, 2014; Doublet, Labarussias, de Miranda, Moritz, & Paxton, 2015). Several studies suggest that the interaction between pesticides and parasites can contribute to declines in wild populations either directly (e.g., mortality) or indirectly when the presence of the pesticide alters the traits of the parasite or the host (e.g., immunosuppression; Christin et al., 2003; Kiesecker, 2002; Rohr, Raffel, Sessions, & Hudson, 2008).…”

Population-specific toxicity of six insecticides to the trematode Echinoparyphium sp.

“…While a diversity of factors can drive disease dynamics, there is growing awareness that human actions may be a significant contributor. Human activities have dramatically altered the environment through climate change, habitat fragmentation, and introduced species, which can directly or indirectly influence disease dynamics (Blaustein and Kiesecker, 2002;Morley et al 2003Morley et al , 2005Daszak et al 2003;Jones et al 2008;Blaustein et al 2011). Recently, the influence of agrochemicals on disease dynamics has garnered attention.…”

Comparative leukocyte morphometric analysis between endemic Anurans from Brazil and the invasive species Lithobates catesbeianus

“…Declines in population are nonrandom in terms of species' ecological preferences, geographic ranges, and taxonomic associations, probably varying between species, populations, and life stages within a population, and most prevalent in Neotropical mountainous stream-associated species (STUART et al, 2004;BLAUSTEIN et al, 2011).…”

“…The amphibian population decline phenomenon is complex in origin and multifactorial in etiology, caused by some of the following identified causes: habitat loss and overutilization, fragmentation, degradation, pathogens, pollution, introduced exotic species, climate change and associated atmospheric processes, and overexploitation, including collection for pet and food industries (STUART et al, 2004;POUNDS et al, 2006;HAMER;MCDONNELL, 2008;BLAUSTEIN et al, 2011). Declines in population are nonrandom in terms of species' ecological preferences, geographic ranges, and taxonomic associations, probably varying between species, populations, and life stages within a population, and most prevalent in Neotropical mountainous stream-associated species (STUART et al, 2004;BLAUSTEIN et al, 2011).…”