Skip to main content
Fig. 1 | BMC Evolutionary Biology

Fig. 1

From: Differential introgression and the maintenance of species boundaries in an advanced generation avian hybrid zone

Fig. 1

The location of 32 marshes along the northeastern coast of the United States where A. caudacutus and A. nelsoni individuals were sampled. Black circles represent allopatric populations from which putatively pure individuals were used for calculating a hybrid index. White circles represent marshes that are outside of the currently hypothesized overlap zone, yet were treated as sympatric populations due to their close proximity to the hybrid zone and evidence of introgressed individuals [50]. Gray circles represent marshes within the hybrid zone and the red star represents the approximate center of the zone, based on geographic cline estimates. The boxplot represents the distribution of hybrid index values for each of the sympatric marshes sampled; the center of the hybrid zone is colored in red. To demonstrate phenotypic differences between the parental species, representative photographs are shown for allopatric nelsoni (top) and caudacutus (bottom). Hybrids do not exhibit a clear intermediate phenotype, but rather display complex combinations of phenotypic traits that do not vary predictably by genotypic class ([42]; see text)

Back to article page