Demographic consequences of the loss of mating opportunities in a two-species reproductive interference system

Reproductive interference (RI) includes any negative effect on reproductive success of females that is induced by interspecific sexual interactions. Although previous population dynamic models of RI have focused on population-level processes (e.g., changes in population size), individual-level processes (e.g., search and courtship by males and subsequent choice by females) have been largely overlooked. In this study, we constructed a discrete-time population dynamic model comprising two species, assuming iterative courtship and mating within each reproductive time period (i.e., individual-level process) and subsequent population dynamics (i.e., population-level process). We assumed that if males (or females) have wide acceptance range to their counterparts, correct courtship (or mating) to conspecifics and incorrect courtship to heterospecifics would increase simultaneously. We also assumed that two species have different demographics (species 1 with higher reproduction and mortality, species 2 with lower reproduction and mortality). We showed that intermediate acceptance range of females mitigated the negative effect of courtship from heterospecific males on mating success. However, the initially more abundant species 1 can be outcompeted by the initially less abundant species 2. This is because the net negative effect of losing mating opportunities due to RI was greater for species 1 with higher mortality than for species 2 with lower mortality. Overall, the results of reproductive success, which are derived only from individual-level processes, are not always consistent with the demographic consequences, which are derived from both individual- and population-level processes. We propose that analyzing the RI system by considering both individual- and population-level processes is necessary.