The extent and costs of reproductive interference among four species of true bug

Abstract

Reproductive interference arises when individuals of one species engage in reproductive activities with individuals of another, leading to fitness costs in one or both species. Reproductive interference (RI) therefore has two components. First, there must be mis-directed mating interactions. Second, there must be costs associated with these mis-directed interactions. Here we consider RI between four species of true bug in the family Lygaeidae, focusing in particular on the fitness consequences to Lygaeus equestris. The species we consider vary in their relationships with each other, including species in the same or different genus, and with or without natural overlap in their geographic ranges. First we show that inter-specific mating interactions, although not a certain outcome, are common enough to perhaps influence mating behaviour in these species (arising in up to 10 % of inter-specific pairings). Second, we show that reproductive interference can seriously reduce female fitness in L. equestris. Importantly, different species impose different costs of RI on L. equestris, with interactions with male Spilostethus pandurus inflicting fitness costs of similar magnitude to the costs of mating with con-specifics. On the other hand, mating interactions with male Oncopeltus fasciatus appear to have no effect on female fitness. In a follow-up experiment, when we allowed competition amongst just females of S. pandurus and L. equestris, the fitness of the latter was not reduced, arguing more strongly for the role of reproductive interference. However, in our final experiments under mass mating conditions with extended ecological interactions (including scope for competition for resources and cannibalism), the costs of RI were less apparent. Our data therefore suggest that the costs of RI will be contextspecific and may act in concert with, or be swamped by, other ecological effects. We suggest that comparative studies of this sort that both mimic naturally occurring reproductive interference events, and also artificially generate new ones, will be necessary if we are to better understand the ecological and evolutionary significance of reproductive interference.

Reproductive interference: ecological and evolutionary consequences of interspecific promiscuity

“…Many studies have suggested an effect of reproductive interference on population growth rates (i.e., demographic reproductive interference) on the basis of an effect on a fitness component (i.e., component reproductive interference) (e.g., Waser 1978a; Andrews et al 1982;Söderbäck 1994;Hettyey and Pearman 2003;Thum 2007;Matsumoto et al 2010;Takakura and Fujii 2010), but a clear distinction between these two types of reproductive interference has not always been made. The explicit distinction between these two types of reproductive interference should help guide the reader of the papers in this Special Feature (e.g., Shuker et al 2015).…”

“…They also provide evidence for habitat partitioning between the native species and an invasive species driven by reproductive interference on the Japanese main island of Honshu, where the invasive species is abundant. Shuker et al (2015) report the results of various laboratory experiments performed with four true bug species. Although they succeed in demonstrating fitness costs of reproductive interference in this system, they also show that heterospecific mating attempts do not always translate into fitness costs; instead, whether fitness costs are detected appears to be context-dependent.…”

Conflicting intersexual mate choices maintain interspecific sexual interactions

“…Nevertheless, reproductive interference has been reported not only in originally allopatric species pairs (e.g., after a biological invasion; Hettyey and Pearman 2003;D'Amore et al 2009;Wang et al 2012) but also in sympatric species pairs that have presumably interacted with each other on an evolutionary time scale (McLain and Pratt 1999;Gröning et al 2007;Noriyuki et al 2012;Shuker et al 2015). Thus, in some sexually interacting sympatric species pairs, RCD appears not to have led to the disappearance of reproductive interference.…”

From storage to delivery: sperm volume and number of spermatozoa inside storage organs and ejaculates in males ofTimogenes elegans(Scorpiones: Bothriuridae)

“…Naretto et al (2016) found something similar in male Salvator lizards, but this time testes mass was affected but sperm number was not. Although there are studies in arthropods about reproductive interference (e.g., Costa-Schmidt & Machado 2012, Shuker et al 2015, to our knowledge, there are no studies that evaluate sperm production between similar species. Timogenes elegans may live in sympatry with one sister species, T. dorbignyi (Guérin-Méneville, 1843).…”