Density-dependent habitat selection alters fitness in a clonal hexapod

Abstract

Density-dependent habitat selection shapes the distribution and abundance of organisms and thus informs our understanding of the eco-evolutionary process. When habitat choice is contingent on an individual’s expectation of fitness, and when organisms are free to occupy the habitat they choose, their occupation of habitat is well described by an ideal free distribution (IFD). But when individuals are related, habitat selection that maximizes inclusive fitness (MAXN) allows cooperative individuals to supplant the IFD. I tested this possibility by measuring the fitness accrued through habitat selection by clonal populations of a common soil hexapod, Folsomia candida. I controlled variation associated with genetics and state-dependence by establishing experimental populations from a single founding mother and growing them under identical conditions. I varied habitat quality by manipulating substrate moisture. I allowed F. candida to choose between habitats and differentiated between IFD and MAXN habitat selection by measuring fitness. Surprisingly, habitat-selecting F. candida alter the expectations of fitness and can thus outcompete otherwise theoretically optimal strategies. My research demonstrates that density-dependent habitat selection is both an ultimate and proximate mechanism driving spatial population dynamics.