FLOWER MORPHOMETRY OF RHIZOPHORA MANGLE (RHIZOPHORACEAE) - GEOGRAPHICAL VARIATION IN MEXICAN POPULATIONS

We explored the patterns of intra-and interpopulation variation in flo wer morphology of the red mangrove, Rhizophora mangle. Twelve populati ons in Mexico were studied: five from the Gulf of Mexico and the Carib bean Sea, and seven from the Pacific Coast. Six metric floral attribut es were measured from a sample of 1370 flowers. Significant difference s among populations were found for all six attributes. Because floral attributes were all correlated, scores derived from principal factor a nalysis were used to describe the variation in Bower morphology. Two f actors explained essentially all of the variance in flower morphology. Corolla and calyx size had a strong effect on factor 1, while gynoeci um size had the higher effect on factor 2. Nested analyses of variance on the scores from both factors revealed significant differences amon g coasts, among populations within coasts, and among plants within pop ulations. Nonetheless, this variation cannot be explained as a result of clinal variation, as indicated by a series of regression analyses. Cluster analysis (UPGMA) showed that a population from the Pacific coa st was clustered together with those of the Atlantic, and the arrangem ent of populations within each coast showed no evident geographical pa ttern. We propose that frequent events of extinction and recolonizatio n by a few individuals, followed by selfing, may produce differentiati on among populations of red mangrove.