Reproductive interference in two ground‐hopper species: testing hypotheses of coexistence in the field

Abstract

Similar to resource competition, reproductive interference may hamper the coexistence of closely related species. Species that utilize similar signal channels during mate finding may face substantial fitness costs when they come into contact and demographic displacement of the inferior species (sexual exclusion) is a likely outcome of such interactions. The two ground-hopper species Tetrix ceperoi and Tetrix subulata broadly overlap in their ranges and general habitat requirements, but rarely co-occur on a local scale. Results from laboratory and field experiments suggest that this mosaic pattern of sympatry might be influenced by reproductive interference. Here, we examine the significance of sexual interactions for these species in the field and test hypotheses on mechanisms of coexistence. Our results show that heterospecific sexual interactions also occur under field conditions, but in contrast to the experiments T. ceperoi was not the inferior species. The number of male mating attempts of both species was strongly correlated with encounter frequencies. Males discriminated between the sexes but not between the species, suggesting an incomplete mate recognition system in both species. The analysis of microhabitat preferences and spatial distribution revealed that habitat partitioning is not a suitable mechanism of coexistence in this system. Instead, the costs of reproductive interference are substantially mitigated by different niche breadths leading to different degrees of aggregation. Despite a considerable niche overlap T. ceperoi displayed a stronger preference for bare ground and occurred more aggregated than T. subulata , which had a broader niche. These differences may reduce the frequencies of heterospecific encounters and interactions in the field. Our results demonstrate that coexistence in the presence of reproductive interference is comparable to resource competition, being strongly influenced by ecological traits of the involved species, such as niche breadth and dispersion pattern.

Niche overlap in allotopic and syntopic populations of sexually interacting ground‐hopper species

“…Unravelling the mechanisms that promote species’ coexistence in species remains a major task in ecological research (Chesson, 2000; Amarasekare, 2003; Morris, 2003; Agrawal et al , 2007) and the same is true for species engaged in interspecific sexual interactions (Gröning & Hochkirch, 2008). While the mechanisms of coexistence have frequently been studied in the context of resource competition, such studies are still sparse in the context of reproductive interference (but see Gröning et al , 2007b). Different from species competing for shared resources, species involved in sexual interactions might increase their fitness mainly by avoiding direct interactions and not by partitioning other niche dimensions, such as food or oviposition sites.…”

“…Singer, 1990), dilution effects from clumped dispersion patterns (e.g. Gröning et al , 2007b) or local abundance (e.g. Söderbäck, 1994), different colonization capabilities or population dynamics (Westman et al , 2002) and evolutionary mechanisms, that is, reproductive character displacement (Brown & Wilson, 1956).…”

Frequent misdirected courtship in a natural community of colorful Habronattus jumping spiders

“…In other species where reproductive interference is costly, habitat partitioning has been suggested as a mechanism that allows species to co-exist (e.g., [47]). In this study, we show that females of four different species of Habronattus do indeed utilize the available microhabitats and light environments slightly differently, which may reduce heterospecific interactions to some extent.…”

Asymmetric reproductive interference between two closely related spider mites: Tetranychus urticae and T. turkestani (Acari: Tetranychidae)

“…InterspeciWc matings between closely related species may result in reproductive interference, a term deWning negative interactions between species that are associated with their mating systems (Gröning et al 2007). Reproductive interference can adversely aVect the population dynamics, abundance, habitat choice and spatial distribution of the species involved (Gröning et al 2007;Hochkirch et al 2007; Konuma and Chiba 2007;Liu et al 2007;Reyer 2008;Thum 2007).…”

“…Reproductive interference can adversely aVect the population dynamics, abundance, habitat choice and spatial distribution of the species involved (Gröning et al 2007;Hochkirch et al 2007; Konuma and Chiba 2007;Liu et al 2007;Reyer 2008;Thum 2007). In some cases, the intensity of reproductive interference reduces population size in an asymmetric manner.…”