GENETIC-STRUCTURE AND DIFFERENTIATION IN METROSIDEROS-POLYMORPHA (MYRTACEAE) ALONG ALTITUDINAL GRADIENTS IN MAUI, HAWAII

The level and distribution of genetic variability within and among Met rosideros polymorpha populations along altitudinal gradients on the is land of Maui, Hawaii were examined to assess the extent of genetic dif ferentiation. Sixteen loci encoding 11 enzymes were scored in 17 popul ations along the NE wet slope of Mt. Haleakala and Kipahulu Valley in East Maui and six populations along the Puu Kukui trail in West Maui. On average, 50 % of the loci were polymorphic within populations with an overall mean of 2.15 alleles per locus. The observed heterozygositi es for different populations were moderate (0.108-0.220) and conformed to panmixia except for one of the mid-elevation populations. The dist ribution of allozyme variation indicates that very little differentiat ion has occurred along altitudinal gradients. Approximately 90 % of th e total variation resides within populations in East Maui while 95 % w as found within West Maui populations. The mean populational pair-wise genetic identities (Nei's I) ranged from 0.909 to 0.998. The UPGMA cl uster analysis on genetic identity matrices and PCA on allele frequenc ies revealed marginal altitudinal differentiation. Twenty one alleles out of a total 63 showed statistically significant correlations with e nvironmental variables.