DYNAMICS AND VIABILITY OF A METAPOPULATION OF THE ENDANGERED IBERIAN LYNX (LYNX PARDINUS)

Abstract

The use of metapopulation models in conservation biology is growing exponentially, but there is a need for empirical studies that support theoretical approaches, especially for species with large and long-lived individuals. In this paper we explore the viability and dynamics of a real metapopulation of an endangered mammal by combining field work and modeling in order to support conservation decisions and evaluate theoretical approaches. The Iberian lynx (Lynx pardinus), considered the most vulnerable felid in the world, is restricted to the Iberian Peninsula in southwestern Europe. The persistence of the species is handicapped by the high fragmentation of its populations. Fewer than 1000 individuals are distributed in nine isolated populations, each of them also fragmented but with their patches connected by dispersers, in what could be called metapopulations. One of these metapopulations, including ∼60 individuals, inhabits the Doñana National Park (DNP) and its surroundings. Demographic and behavioral data gathered over one decade for this lynx population were employed to develop a spatially realistic structured model with density-dependent fecundity and migration, including demographic and environmental stochasticity. Such a model is used to identify the demographic features that determine the dynamics of this population and to predict its risk of decline under a set of alternative assumptions. A hypothetical lynx metapopulation with values of the parameters such as those observed in Doñana, but without stochastic events, could sustain itself over time. Results of this deterministic model show how females occupy all the potential breeding territories, while males are below the carrying capacity. The metapopulation has a source–sink structure, with the sources internal and the sinks external to the national park. Sinks result from reduced survival rather than reduced fecundity, as generally assumed. High mortality in sink patches is deterministic, deriving both from within-patch risks and from factors related to the landscape matrix among patches. The survival rate of adults with territories in the sources was the most sensitive parameter, leading the dynamics of the metapopulation. When we include demographic stochasticity in the model, the population becomes extinct 22% of the time within 100 yr, and this value increases to 33.8% when environmental stochasticity is also considered. Most of the metapopulation extinctions occurred because of the disappearance of males due to sex differences in demographic parameters related to behavioral aspects (e.g., dispersal rate). Different scenarios were simulated as modifications affecting either within- or between-patch dynamics. Changes in the carrying capacity of source and sink patches would have very differentconsequences in terms of metapopulation persistence: one breeding territory increase in the largest source reduces metapopulation extinction risk from 33.8 to 17.2% in 100 yr, while an increase of three territories in the largest sink does not modify the extinction risk. In this sense, results suggest that the best management strategy for conservation should be restoring habitat at the source patches and reducing mortality at the sinks. The results of our models emphasize the need for empirical studies to characterize metapopulations in nature and distinguish between such terms as source–sink, mainland–island, nonequilibrium, or even “refuge” metapopulations.