Abstract
AbstractReproductive 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 context‐specific 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.
Highlights
Interspecific interactions can take many forms and play a vital role in shaping evolution
Whilst there appears to variation in mating rates across the species, these observations confirm the relative ease with which heterospecific mating attempts occur in these species, at least in the laboratory environment
As we did not mark individuals, our experimental design means that any differences in mortality detected between the equestris–equestris and equestris-pandurus treatments could be partly explained by sampling the same L. equestris longevity distribution twice and taking the earliest mortality as opposed to only sampling the distribution once
Summary
Interspecific interactions can take many forms and play a vital role in shaping evolution. Reproductive interference (RI) arises when reproductive behaviours occur between individuals of different species and these behaviours result in a loss of fitness for one or both species (Groning and Hochkirch 2008; Burdfield-Steel and Shuker 2011). Popul Ecol (2015) 57:321–331 misdirected courtship and copulation with heterospecifics These latter forms of RI are thought to entail the highest costs (Rhymer and Simberloff 1996). While inter-species sexual behaviours are well-documented (Andrews et al 1982; Dame and Petren 2006; de Bruyn et al 2008), the ecological effects of such interactions are still poorly understood (Groning and Hochkirch 2008). More empirical studies of the fitness costs of reproductive interference are needed in order to establish if this is a typical outcome (Groning and Hochkirch 2008)
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