Stable coexistence of ecologically identical species: conspecific aggregation via reproductive interference

Abstract

Stable coexistence of ecologically identical species is not possible according to the established ecological theory. Many coexistence mechanisms have been proposed, but they all involve some form of ecological differentiation among the competing species. The aggregation model of coexistence would predict coexistence of identical species if there would be a mechanism that generates spatially aggregated distributions that are not completely correlated among the species. Our aim is to demonstrate that continued dispersal, triggered by reproductive interference between ecologically identical species, is such a mechanism. This study has been motivated by species using ephemeral patchy resources, such as decomposing fruits, fungal sporophores, carrion, and dung. We analyse an individual-based model with sexual reproduction, in which the progeny develops in ephemeral resource patches and the new generation disperses to a new set of patches. We assume spatially restricted dispersal, that patches differ in detectability, and that unmated females continue dispersal. In the model, reproductive interference (males spend some time searching for and/or attempting to mate with heterospecific females) reduces the mating rate of females, especially in the less common species, which leads to increased dispersal and reduces spatial correlation in species' distributions. For a wide range of parameter values, coexisting species show a systematic difference in their relative abundances due to two opposing forces: (1) uncommon species have reduced growth rate (Allee effect), which decreases abundance; (2) an abundance difference between the species reduces interspecific spatial correlation, which in turn reduces interspecific competition and allows the rarer species to persist at low density. Our results demonstrate a new mechanism for coexistence that is not based on ecological differentiation between species.

Causes and Consequences of Behavioral Interference between Species

“…However, under special circumstances, reproductive interference could promote coexistence between ecological competitors. For example, ecologically identical species that exploit ephemeral food patches might be able to coexist if reproductive interference triggers dispersal that reduces interspecific spatial overlap [24].…”

“…However, under special circumstances, reproductive interference could promote coexistence between ecological competitors. For example, ecologically identical species that exploit ephemeral food patches might be able to coexist if reproductive interference triggers dispersal that reduces interspecific spatial overlap [24].Aggressive interference is also expected, in most cases, to hasten competitive exclusion [22] Shifting geographical ranges are natural features of biodiversity over longer timescales. However, the rate at which species colonize new environments has increased dramatically because of climate change, land-use change, and the introduction of alien species.…”

Reproductive interference in insects

“…What causes reproductive interference? The ecological factors influencing RI have already been thoroughly reviewed, as have some of the ecological consequences of RI, such as species coexistence, sexual exclusion, and ecological character displacement (Kuno, ; Gröning & Hochkirch, ; recent examples include Kyogoku, ; Noriyuki & Osawa, ; Ruokolainen & Hanski, ). Given space constraints though, we will focus on the evolution of mating systems, including the evolutionary causes and consequences of polyandry, sexual selection, and sexual conflict on RI.…”

Potential costs of heterospecific sexual interactions in golden orbweb spiders (Nephila spp.)

“…In the case of reproductive interference, the locally dominant species could also suffer from sperm depletion if too many males are failing to arrive at the correct/conspecific females, therefore also suffering a reduction in reproductive output. Such dynamics have been hypothesized to maintain the coexistence of ecologically identical species26.…”

“…A model of coexistence through reproductive interference26 applies to species using ephemeral patchy resources, which does not apply to our focal species. More inclusive population and ecological models may illuminate implications of reproductive interference for rare species like N. komaci , living in habitats of continuous resources (see Supplementary material 1).…”