Reproductive interference is widespread, despite the theoretical expectation that it should be eliminated by reproductive character displacement (RCD). A possible explanation is that females of sympatric species are too similar phenotypically for males to distinguish between them, resulting in a type of evolutionary dilemma or 'catch-22' in which reproductive interference persists because male mate recognition (MR) cannot evolve until female phenotypes diverge further, and vice versa. Here we illustrate, and test, this hypothesis with data on rubyspot damselflies (Hetaerina spp.). First, reproductive isolation owing to male MR breaks down with increasing interspecific similarity in female phenotypes. Second, comparing allopatric and sympatric populations yielded no evidence for RCD, suggesting that parallel divergence in female coloration and male MR in allopatry determines the level of reproductive isolation upon secondary contact. Whenever reproductive isolation depends on male mate recognition and females of sympatric species are phenotypically similar, the evolutionary catch-22 hypothesis offers an explanation for the persistence of reproductive interference.
Dataset1
Dataset1.csv dataset containing reproductive isolation index and indices of similarity for each species pair at each site. Columns: 'male.sp' - species epithet; 'treename' - name as it appears in 'Hetaerina_phylogeny.tree' (see below); 'hs.female.sp' - specific epithet of heterospecific female; 'treename.HS' - name of heterospecific species as it appears in 'Hetaerina_phylogeny.tree' (see below); 'site' - site identity; 'n.conspecific.trials' - number of trials with data from conspecific females; 'n.heterospecific.trials'- number of trials with data from heterospecific females; 'comparison' -index of comparison (used in permutation and phylogenetic analyses); 'note' - explains where measurements of females are from in the case of translocation experiments; 'diff.photographic.lightness'- index 1 in Table A3 ;'overlap.photo.lightness' - index 2 in Table A3 ;'prop.hs.misidentified.as.focal.by.dfa.PHOTO1'- index 3 in Table A3 ;'prop.hs.misidentified.as.focal.by.dfa.PHOTO2' - index 4 in Table A3 ;'diff.weighted.spec.lightness' - index 5 in Table A3 ;'prop.hs.misidentified.as.focal.by.dfa.SPEC'- index 6 in Table A3 ;'propclasp.hs' - proportion of successful trials where a male of the focal species responded sexually to the indicated heterospecific female ;'propclasp.cs'- proportion of successful trials where a male of the focal species responded sexually to conspecific females ;'isolation.index' - calculated from Eq. 1 in the main text
Dataset2A
Dataset2A.csv contains species means and standard deviations for photographic ("*weighted*" columns) and spectrophotometric indices ("tot.int*" columns) of female wing colouration (used in phylogenetic simulation analyses in Script2.R)
Dataset2B
Dataset2B.csv contains site X species means and standard deviations for photographic ("*weighted*" columns) and spectrophotometric indices ("tot.int*" columns) of female wing colouration (used in phylogenetic simulation analyses in Script2.R)
Dataset3
Dataset3.csv contains data used to conduct analyses of wing darkening and translocation experiments (see analyses in Script3.R). Columns: 'id'- unique id for each territory holder; 'male.sp'- species of territory holder; 'site'- code used for the population where male is a territory holder; 'female.treatment'- treatment of tethered female'; 'wing.darkening'- data used in analyses of wing darkening experiments; 'translocation' data used in analyses of translocation experiments.
Hetaerina_phylogeny
Hetaerina_phylogeny.tree is the ultrametric, maximum clade credibility phylogeny file used in phylogenetic analyses
IsolationByDistance
IsolationByDistance.csv contains pairwise Fst and distance measurements, and a variable indicating whether two populations are found in the same drainage
Script1
Script1.R contains an R script that runs Spearman correlation analyses, including permutation analyses for cases where phenotypic similarity index is the same for both species in the comparsion
Script2
Script2.R contains an R script with code used to conduct phylogenetic simulation analyses.
