Extended Analysis of Hybridization in Sunfishes (Centrarchidae) Using an Adjusted Hybrid Index Method
Sunfish collected from Pinehurst Lake, Ontario, were sorted into three groups: bluegill (Lepomis macrochirus), pumpkinseed (L. gibbosus), and a group possessing some of the color patterns of each of the other two. Eleven morphological characters of each fish were analyzed by a hybrid index method, and by an adjusted index which allowed: a) calculation of sampling variances of individual and mean index estimates and, b) testing of hypotheses about the position of suspected hybrids relative to the parental populations. This method, applied to single characters and to combinations of characters, showed that the anomalous group resembled bluegills in four characters, pumpkinseeds in one, and were exactly intermediate in the others. The simplest explanation of these results is that the intermediate group was a population of bluegill × pumpkinseed hybrids.This use of the hybrid index permits increased precision over earlier methods in comparing suspected hybrid individuals with their putative parent populations.