Individual variation in life history characteristics can influence extinction risk

The white sturgeon (Acipenser transmontanus) shows great individual variati on in the age at maturation. This study examines the consequences of model assumptions about individual variation in the age at maturation on predicte d population viability. I considered: (1) the effects of variation in age a t maturation alone; (2) the effects of heritability; and (3) the influence of a stable and an altered selective regime. Two selective regimes represen ted conditions before and after the impoundment of a river, blocking access of anadromous white sturgeon populations to the ocean. In contrast to prev ious simulation studies, I found that increased individual variation in the age at maturity did not necessarily lead to a higher likelihood of persist ence. Individual variation increased the simulated likelihood of persistenc e when the variation was heritable and the selective regime had changed suc h that the mean age at maturity was no longer optimal. (C) 2001 Elsevier Sc ience B.V. All rights reserved.