Population diversity and the portfolio effect in an exploited species

摘要: One of the most pervasive themes in ecology is that biological diversity stabilizes ecosystem processes and services they provide to society, a concept has become common argument for biodiversity conservation. Species-rich communities are thought produce more temporally stable because complementary or independent dynamics among species perform similar functions. Such variance dampening within referred as portfolio effect analogous effects asset on stability financial portfolios. In ecology, these arguments have focused but not considered importance biologically relevant individual species. Current rates population extirpation probably at least three orders magnitude higher than extinction rates, so there pressing need clarify how life history affect performance providing important services. Here we use five decades data from Oncorhynchus nerka (sockeye salmon) Bristol Bay, Alaska, first quantification derive an heavily exploited Variability annual Bay salmon returns 2.2 times lower it would be if system consisted single homogenous rather several hundred discrete populations currently consists of. Furthermore, were homogeneous population, such increased variability lead ten frequent fisheries closures. Portfolio also evident watershed food webs, where stabilize extend predator access resources. Our results demonstrate critical maintaining stabilizing securing economies livelihoods depend them. The reliability will erode faster indicated by loss alone.