Fig. 6From: Differential introgression and the maintenance of species boundaries in an advanced generation avian hybrid zoneVariance for five morphological traits plotted for 22 sympatric nelsoni and caudacutus marshes along the sampling transect (254 individuals): bill length (top left), plumage coloration (top middle), plumage definition (top right), weight (bottom left), and wing chord (bottom middle). V max, calculated as the maximum variance expected under a scenario of reproductive isolation, is plotted as a blue line. Traits with variance closer to V max have reduced introgressionBack to article page