Reproductive interference via display signals: the challenge of multiple receivers

Abstract

Sexually selected traits important in both mate and competitor recognition provide an opportunity to understand the tradeoffs associated with reproductive and competitive interference. When co-occurring species compete over similar resources, selection may promote signal similarity to facilitate competitive interactions in opposition to selection for signal divergence to maintain assortative mating. Bird song provides a classic example of contrasting selection on signal design, because songs function both in mate discrimination and in territorial advertisement. Similarity in songs aids competitor recognition both within and across species, and song convergence or mixing is widespread in the songbirds. Two related mechanisms can maintain mate recognition in the face of song convergence. First, multiple recognition signals, both across and within signaling modalities, provide a basis for mate and competitor discrimination using different sets of cues. Second, stricter female song preferences may allow interspecific male-male competitive communication without compromising female mate discrimination. I suggest that increased understanding of the neurobiology underlying song recognition will provide insight into the relative importance and prevalence of these different mechanisms along a continuum of species divergence.

Evolutionary and biogeographical support for species-specific proteins in lizard chemical signals

“…Consequently, selective pressures are expected to promote divergence in species traits involved in species recognition, to reduce detrimental interactions, but only where they occur in sympatry. We do acknowledge that our survey sampled just one population per species, precluding the explicit analysis of the effect of sympatric congeners at the within-species level (Collyer & Adams, 2007;Wheatcroft, 2015). Nonetheless, our comparison of species within the ecologically homogeneous group of wall lizards revealed that the protein signal diverged more in those species pairs with higher geographic overlap.…”

Reproductive character displacement of female, but not male song discrimination in an avian hybrid zone

“…Second, stricter song discrimination could result from divergence in genes underlying the perceptual system involved in song recognition (e.g., Haavie et al. ; Wheatcroft and Qvarnström ). For example, genetic variation across species underlies discrimination of conspecific song in nestling flycatchers (Wheatcroft and Qvarnström accepted).…”

“…A key prediction of this mechanism is that females from allopatric populations should discriminate against heterospecific songs. Second, if time in allopatry is insufficient, sympatry itself may promote stricter song discrimination either as a result of direct selection to avoid heterospecific songs to reduce mixed pairing (i.e., reinforcement; Hudson and Price 2014;Wheatcroft 2015), learning to avoid heterospecific songs due to costly behavioral interactions (Verzijden et al 2012b), or a byproduct of other evolutionary forces, such as ecological displacement (Pfennig and Pfennig 2009). In this case, only females from sympatric populations should discriminate against heterospecific songs.…”

Heterospecific mating interactions as an interface between ecology and evolution

“…Females, on the other hand, can potentially reduce the costs of such pairings by extra‐pair mating with conspecific males (Svedin, Wiley, Veen, Gustafsson, & Qvarnström, 2008; Veen et al., 2001; but see also Knief, Bossu, & Wolf, 2020). As a result, in such systems, there may be particularly strong selection on male signalling traits, which should aid rapid divergence (Wheatcroft, 2015). Furthermore, whereas strong selection on females is likely to have substantial demographic effects, selection on males may little reduce population growth.…”