Life-history correlates of extinction risk and recovery potential

Abstract

Extinction risk is inversely associated with maximum per capita population growth rate (rmax). However, this parameter is not known for most threatened species, underscoring the value in identifying correlates of r max that, in the absence of demographic data, would indirectly allow one to identify species and populations at elevated risk of extinction and their associated recovery potential. We undertook a comparative life-history analysis of 199 species from three taxonomic classes: Chondrichthyes (e.g., sharks; n = 82), Actinopterygii (teleost or bony fishes; n = 47), and Mammalia (n = 70, including 16 marine species). Median rmax was highest for (and similar between) terrestrial mammals (0.71) and teleosts (0.43), significantly lower among chondrichthyans (0.26), and lower still in marine mammals (0.07). Age at maturity was the primary (and negative) correlate of rmax. In contrast, although body size was negatively correlated with rmax in chondrichthyans and mammals, evidence of an association in teleosts was equivocal, and fecundity was not related to rmax in fishes, despite recurring assertions to the contrary. Our analyses suggest that age at maturity can serve as a universal predictor of extinction risk in fishes and mammals when rmax itself is unknown. Moreover, in contrast to what is generally expected, the recovery potential of teleost fishes does not differ from that of terrestrial mammals. Our findings are supportive of the application of extinction-risk criteria that are based on generation time and that are independent of taxonomic affinity. © 2012 by the Ecological Society of America.