Fig. 6

Variance 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 introgression