Living on the edge: Species trait synergisms and the predisposition of endemic desert fishes to rarity, extirpation and extinction.
Olden, Julian*,1, Poff, N. LeRoy2, Bestgen, Kevin 3, 1 Center for Limnology, Madison, Wisconsin, USA2 Department of Biology, Fort Collins, Colorado, USA3 Department of Fishery and Wildlife Biology, Fort Collins, Colorado, USA
ABSTRACT- The causes and consequences of species extinctions remain a central question in conservation biology and predictive suites of ecological and life-history traits have proven to provide reasonable estimates of species extinction risk across a diverse array of taxonomic groups. The literature is replete with studies linking individual traits to perceived risk of global extinction, yet the manner in which trait synergisms (i.e., non-additive interactions among traits) may differentially contribute to species rarity, local probability of extirpation and risk of global extinction has never, to our knowledge, been examined. The present study conducts this analysis for the native freshwater fishes of the Colorado River Basin, a gravely endangered, highly endemic fish fauna in the United States, by relating a comprehensive suite of morphological, behavioural, physiological and life history traits to empirical-based estimates of species rarity and probability of extirpation, and expert-based estimates of perceived extinction risk to habitat degradation and interactions with non-native fishes. Our results point strongly to the importance of trait synergisms in rendering fish species more or less vulnerable to different levels of perceived extinction risk from different sources of threat, and they provide the first empirical evidence supporting the commonly-held assumption that the attributes of species that contribute to their rarity will further predispose them to local extirpation and global extinction. Moreover, our results highlight the subtle manner by which traits may differentially influence species risk of extirpation versus extinction; in that particular trait combinations were related to increased probability of local extirpation, but decreased risk of global extinction of native fishes. Thus, the intrinsic traits of species can enhance predictive conservation biology, although such advances are only likely to be achieved from studying trait synergisms and partitioning the extinction process according to species rarity, local probability of extirpation, and perceived level of global extinction from different ecological threats.
Key words: ecological niche, life-history traits, native biodiversity, river regulation
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