Reconciling social interaction with habitat selection in territorial species.

The concept of habitat selection as the primary force in clustered distributions has been challenged by behavioral studies of conspecific attraction. This has lead to two conflicting explanations for settlement behavior, which we have integrated into one model. This model creates a range of fitness outcomes for different settlement strategies, encompassing the four combinations of positive and negative effects of the habitat selection and social interaction. It expands the ideal free distribution models (negative intra-specific interactions and positive habitat selection), to consider alternative situations where (1) beneficial social interaction increases fitness for clustered pairs in poor quality habitat, (2) neither habitat selection nor conspecific attraction can improve fitness, and (3) where both are beneficial and do not interfere with each other. The model does this by establishing an intrinsic fitness, where the effects of both habitat selection (h) and conspecific attractions (c) are neutral (h=c=1) and do not influence settlement. Clustered distributions occur when h·c>1 because the fitness in clusters is greater than intrinsic fitness. Dispersed distributions occur when h·c<1 and fitness is lower than the intrinsic. The benefit of the model is that it allows conspecific attraction to be considered a positive force in fitness without rejecting the proven concept of ideal free distribution.