Habitat Selection and the Evolution of Specialists in Heterogeneous Environments

Abstract

Recent advances in studies of habitat selection and resource use provide a framework not only for estimating resource specialization, but also for predicting future success of specialist and generalist strategies. The protocol merges resource selection functions with fitness and population dynamics to assess the evolution of competing strategies that change with density-dependent habitat selection. These strategies are revealed by resource selection coefficients derived from marked individuals that can then be used to predict each individual's fitness at different population sizes. Simulated consumer resource dynamics confirm the theory's ability to identify strategies of habitat and resource use with simple statistical models that summarize rather complex systems. The theory produces excellent fits with simulated data when strategies depend on density, and when the success of a single strategy interacts with others. Specialist strategies yield highest fitness at low population density, whereas generalists have highest fitness in dense populations. When applied to female red deer living on the Isle of Rum, Scotland, the theory correctly predicts an equilibrium distribution of competing strategies dominated by specialization on Agrostis/Festuca grassland. Specialization declined as population density increased through time. Simultaneously, changes in the genetic structure of the population reflected the increased opportunity for outbreeding as individuals became less specialized. Thus, it appears that theory effectively assessed competing strategies of resource use, and predicted their density- and frequency-dependent evolution.

Keywords:

• evolutionary strategies
• generalists
• habitat selection
• population dynamics
• red deer
• resource selection functions
• specialists