Assortative mating is of interest because of its role in speciation and the maintenance of species boundaries. However, we know little about how within-species assortment is related to interspecific sexual isolation. Most previous studies of assortative mating have focused on a single trait in males and females, rather than utilizing multivariate trait information. Here we investigate how intraspecific assortative mating relates to sexual isolation in two sympatric and congeneric damselfly species (genus Calopteryx). We connect intraspecific assortment to interspecific sexual isolation by combining field observations, mate preference experiments and enforced copulation experiments. Using canonical correlation analysis, we demonstrate multivariate intraspecific assortment for body size and body shape. Males of the smaller species mate more frequently with heterospecific females than males of the larger species, which showed less attraction to small heterospecific females. Field experiments suggest that sexual isolation asymmetry is caused by male preferences for large heterospecific females, rather than by mechanical isolation due to interspecific size differences or female preferences for large males. Male preferences for large females and male-male competition for high quality females can therefore counteract sexual isolation. This sexual isolation asymmetry therefore indicates that sexual selection currently opposes a species boundary.
Assortative mating data from "Klingavälsåns Naturreservat"
Male and female mating couples and morphological data in mating pairs from "Klingavälsåns Naturreservat". Male and female ID:s and date of capture are given (male above the female he was mating with), and value for each of the eight measured morphological traits that we measured. These trait values were used to estimate the strength of assortative mating.
AssortativeMatingCompletePairsKlingavalsan.csv
Assortative mating data from "Sövdemölla"
Male and female mating couples and morphological data in mating pairs from "Sövdemölla". Male and female ID:s and date of capture are given (male above the female he was mating with), and value for each of the eight measured morphological traits that we measured. These trait values were used to estimate the strength of assortative mating.
AssortativeMatingCompletePairsSovdemolla.csv
Combined assortative mating data from both localities (trait values centred by mean)
Male and female mating couples and morphological data in mating pairs from "Klingavälsåns Naturreservat" and "Sövdemölla" (both populations combined, morphological trait data centred to mean zero). Male and female ID:s and date of capture are given (male above the female he was mating with), and value for each of the eight measured morphological traits that we measured. These trait values were used to estimate the strength of assortative mating.
DataCentered.csv
Combined assortative mating data from both localities (trait values scaled to mean zero and unit variance))
Assortative mating data (male and female trait values; scaled to mean zero and unit variance) from "Klingavälsåns Naturreservat" and "Sövdemölla" (combined). Eight morphological traits were measured in both males and females, and each male that was found copulating with his female is given (male above, female below).
DataScaled.csv
Male mate preferences for con- and heterospecific females (Fig. 4)
Dataset behind Fig. 4, showing Calopteryx male mate preferences for con- and heterospecific females in field presentation experiments."Score" shows male mating response. Female ID, year and population are also given.
MalePreferences.txt
R-script for analyzing male mate preferences (Fig. 4)
R-script to analyze male mate preferences (binomial variable) using a Generalized Linear Model (GLZ). Results are presented in Fig. 4, and the dataset is provided as another file in DRYAD associated with this paper.
RScriptFig4.txt
R-script for CCA-analyses (Table 2 and Table S6)
R-script behind the Canonical Correlation Analyses (CCA) presented in Table 2 and Table S6.
RScriptTable2TableS6.txt
R-script for Table S1
R-script behind the analyses for Table S1.
RScriptTableS1.txt
R-script for Table S2 (factor loadings)
R-script behind the analyses in Table S2 (factor loadings).
RScriptTableS2.txt
R-script behind Table S3 (calculating individual scores)
R-script behind the calculations of individual scores in Table S3.
RScriptTableS3.txt
R-script behind Table S4 (CCA:s for each species separately)
R-script behind the Canonical Correlation Analyses (CCA:s) for Calopteryx splendens and C. virgo (Table S4).
RScriptTableS4.txt
R-script (Table S5) and data on female mating preferences
R-script and dataset (N=30 males) behind analyses in Table S5 on female mating preferences in relation to male body size and male wing patch characteristics.
RScriptTableS5.txt
RScript behind Table S6 (four separate Principal Component Analyses)
R-script for Principal Component Analyses (PCA:s) of the eight morphological traits of all four phenotypes (C. splendens males and females and C. virgo males and females). Results are given i Table S6.
RScriptTableS6.txt
