Abstract
Dispersal can augment viability of small populations, but this effect is contingent on successful post-dispersal reproduction of individuals. Nonetheless, variation in post-dispersal reproductive success is frequently ignored, such that dispersal (movement between fragments) and effective dispersal (movement followed by reproduction) are often viewed interchangeably. Mate choice by females can potentially limit or augment post-dispersal reproductive success of males and is predicted to vary with the distance dispersed. Consequently, mate choice may impact effective dispersal rates, but this issue is poorly understood. We use a multi-fragment, individual-based model to investigate if distance-mediated mate choice limits effective dispersal, in the absence of, and in combination with, distance-limited dispersal. We considered four scenarios of distance-mediated mate choice such that it was (a) spatially uniform, dispersers were (b) preferred or (c) avoided, and (d) females showed preference for dispersers that moved intermediate distances. We tested if mating system and sex-biased dispersal influence the role of mate choice on effective dispersal. We parameterized our model using previously published demographic data on the chimpanzee Pan troglodytes; however, we intend the model to be generalizable to many species and scenarios considered extend beyond observed chimpanzee behaviour. Mate choice induced distance-dependent patterns of effective dispersal among populations, which, under certain conditions, surpased impacts of distance-limited dispersal. When distance suppressed both dispersal and mate choice, the two additively decreased effective dispersal at large distances. When dispersers were preferred, the effects of mate choice and limited dispersal negated each other to a degree determined by the relative spatial scale of the two processes. Effects of mate choice on effective dispersal can lead to misleading conclusions on dispersal barriers when inferred through indices that reflect effective dispersal. Isolating constraints to effective dispersal can enhance our understanding of connectivity and can identify key needs for connectivity conservation.
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