Department of Biological Sciences. University of Arkansas, United States
Background/Question/Methods
Ecological communities exist in a dynamic state of flux as species are gained and lost. Global climate change has made this dynamical state especially evident as species ranges shift, expand, and contract to create novel communities. Yet successful dispersal and establishment into existing communities is challenging because resident species can locally adapt to environmental conditions and increase their population size, imposing strong costs due interspecific competition on later arriving species and preventing them from establishing a population. However, local adaptation can also have fitness costs. One such cost is through sexual conflict, whereby male reproductive strategies generate fitness costs on females. Therefore, sexual conflict can affect population persistence by its effects on female fitness. Importantly, the strength of sexual conflict often increases as populations locally adapt. This trade-off between local adaptation and sexual conflict could therefore facilitate competitor species invasions. To explore this idea, we use a theoretical model simulating a range expansion scenario in which a species invades a new environment occupied by a locally adapted heterospecific competitor. We evaluate how local adaptation can mediate the effects of sexual conflict, promote species invasion, and stabilize competitor coexistence.
Results/Conclusions
Three key points emerged from our model simulating range expansions. First, even weak costs of sexual conflict facilitate invader establishment, but the stronger the sexual conflict the more common an invading species can become, and, in some cases replace the resident. Second, interspecific competition has a surprisingly limited effects on invader establishment and can instead promote coexistence. Third, even when initial invader population sizes are small, subtle sexual conflict in the resident can be critical in facilitating invader establishment. Rather than acting as an eco-evolutionary barrier that constrains the assembly of communities, we show that the costs of local adaptation through sexual conflict can act as a window for the successful establishment of species under range expansion, increasing species turnover. More generally, our results show that moving away from purely ecological models by including additional species interactions that determine population fitness, such as sexual conflict, will be insightful for understanding how community assembly and the maintenances of species diversity will unfold in a changing world.
