Competition for food affects the strength of reproductive interference and its consequences for species coexistence

Abstract

Competition for food and negative interspecific sexual interactions (reproductive interference) have been identified as major drivers of species exclusion. These interactions likely do not act independently, as they often involve the same actors and may be modulated by the same underlying traits. However, how they determine competitive dominance when acting in combination has not yet been studied. Here, we address this issue using two closely related species, the spider mitesTetranychus urticaeandT. cinnabarinus. First, by measuring species interactions in small-scale experiments, we revealed that the strength and symmetry of reproductive interference between species changed in presence of food competition. Next, using a population model, we showed that such non-additive effects induce significant changes in predicted competitive outcomes, specifically, a change in priority effects from favouring the inferior competitor for food in the sole presence of reproductive interference to favouring the superior competitor instead. Finally, we confirmed the accuracy of the model predictions for short-term population dynamics in a large-scale experiment. Together, these lines of evidence show that food competition and reproductive interference have non-additive effects on the population dynamics of interacting species, and highlight the necessity of incorporating both mechanisms to better predict competitive outcomes.

Wolbachiastrengthens the match between pre-mating and early post-mating isolation in spider mites

“…Cruz et al 2021) to promote the exclusion of the red form population ( cf. Grether et al 2017; Cruz et al 2023). Conversely, homotypic mating preference by red males should decrease the strength of reproductive interference for the red population, as it reduces the prevalence of crosses between green females and red males (hence the overproduction of green males stemming from these crosses) and should prevent (non-choosy) red females from having a higher chance to mate with a green male.…”