POPULATION-DYNAMIC PRINCIPLES

Although the causes of population extinction, locally and globally, ar e many, varied and idiosyncratic when individual species are considere d, there are nevertheless some basic general constraints and ground ru les that make some species more extinction-prone than others. This pap er reviews their implications for the ultimate and proximate causes of extinction. Phenomena reviewed include: a positive correlation betwee n local abundance and size of geographic range, putting some populatio ns in 'double jeopardy'; smaller average range sizes in the tropics; m etapopulation dynamic processes that can spread risk, but only if the spatial correlation between fluctuations of conspecific populations is low; the influence of body size and trophic position; and phylogeneti c constraints on range sizes and abundance.