Male Calopteryx splendens (a) have a melanized wing patch, unlike females (b), which have transparent wings. The wing patch is a target of intra- and intersexual selection and functions as a sexual isolation character against the sympatric congener, the beautiful demoiselle Calopteryx virgo (males: c, females: d). Although males (a,c) of both species have melanized wings, note the interspecific difference in the amount of melanization between both males (a,c) and females (b,d).
The graphs illustrate the magnitude of estimated of gene flow (migration rate: m) between C. splendens populations that were either allopatric (three populations designated ‘A’; containing only C. splendens) or sympatric (four populations designated ‘S'; containing both C. splendens and C. virgo). For explanations of population abbreviations, see electronic supplementary material, table S1. (a) Matrix of migration rates (m) between all seven populations, estimated using BayesAss 3 (electronic supplementary material). (b) Estimates of m within ecological categories (i.e. allopatric to allopatric and sympatric to sympatric versus allopatric to sympatric and sympatric to allopatric).
Population divergence in mate preferences towards con- and heterospecific mates in allopatric (A1–A4) and sympatric populations (S1–S4). Line at ‘1.0’ shows the standardized average response towards conspecific mates. Open symbols shows mean (±95% CIs) response towards conspecifics, and closed symbols mean response (±95% CIs) towards heterospecifics. (a) Female population divergence (two-way ANOVA: population (P): F7,395 = 35.475, p < 0.001; species (S): F1,395 = 4.217, p = 0.04; P × S: F7,395 = 24.828, p < 0.001). (b) Male population divergence (two-way ANOVA: population (P): F6,205 = 8.741, p < 0.001; species (S): F1,205 = 853.357, p < 0.001; P × S: F6,205 = 9.852, p < 0.001). (c) Elevated population divergence in female and male mate preferences towards heterospecifics in allopatric versus sympatric populations (nested mixed model analysis: sex × population ecology: F1,226 = 13.640; p = 0.003; electronic supplementary material, table S2: Model 2).
Mate responses of sexually naive C. splendens males and females towards con- and heterospecific mates of the opposite sex. (a) Mean (±s.e.) mate responses of sexually naive C. splendens males towards conspecific females and heterospecific females. These sexually naive males showed a significantly lower response towards heterospecific females, compared with their response towards conspecific females (paired t-test: t1,29 = 2.713; p = 0.011). (b) Mean (±s.e.) mate responses of sexually naive C. splendens females towards conspecific and heterospecific males. There was a significant effect of female population origin (Klingavälsån or Höje Å) on mean mate responses (F1,193 = 27.314; p < 0.001), but no there was no significant difference in the strength of naive female responses towards con- and heterospecific males (F1,193 = 0.067; p = 0.80). (c) Comparison between sexually naive female and male C. splendens in their mean response towards heterospecific putative mates (line at 1.0 indicates the average standardized response towards conspecifics). Means (±95 CIs) are shown (data only from Klingavälsån). Sexually naive female C. splendens do not discriminate against heterospecifics mates, unlike sexually naive male C. splendens (ANOVA for effect of sex: F1,60 = 12.903; p = 0.001).