Determination and Interpretation of Comigrating Allozymes among Genera of the Benincaseae (Cucurbitaceae)

ABSTRACr. The extent to which allozyme comparisons are possible at and above the generic level was evaluated for eight species representing six genera and both subtribes of the tribe Benincaseae (Cucurbitaceae). We employed various starch gel electrophoretic conditions to investigate and combat the problem of comigration of enzymes between taxa. Fifteen enzyme systems were resolved on an average of four gel/electrode buffer systems each. We detected comigration at approximately two-thirds of the 30 resolved loci. Comparison of our results to those we might have obtained using single and two-condition electrophoresis revealed that a substantial proportion of intergeneric differentiation would have gone undetected with single-condition electrophoresis. Two testing conditions per enzyme would have been sufficient in most cases, however. Comparison of single versus multiple-condition electrophoresis also indicated that undetected comigration generally increases with increasing genetic differentiation of taxa. Deviations from this trend suggest additional unknown influences. All taxa were allozymically connected, either directly or via other taxa in the study. Evaluation of taxon relationships was based on the percentage of loci at which two taxa shared an allele. Results from this analysis are in concordance with geographical, biochemical, and cytological data suggesting three major evolutionary lineages within the tribe Benincaseae. This, in turn, validates the utility of allozyme analysis for systematic work at and above the generic level where divergence is not too great.