Biosystematic studies of the red algal genus Eucheuma. I. Electrophoretic variation among Florida populations

Electrophoretic techniques were used to assess the degree of genetic differentiation among 4 species of the seaweed Eucheuma; E. isiforme, E. nudum, E. gelidium and E. acanthocladum. Nine Floridian populations were surveyed for 5 enzymes (14 loci), and compared using both phenotypic identity (I _p )and Nei's genetic identity (I) statistics. Results suggest there is a very high degree of genetic similarity between E. isiforme and E. nudum (=0.904), and between E. gelidium and E. acanthocladum (=0.857), but a very low degree of similarity between these two pairs of species (=0.372). These findings are in agreement with an earlier report which recommended the removal of E. gelidium and E. acanthocladum from the genus based on differences in reproductive anatomy. Greater genetic similarity was observed among the E. isiforme populations than among the E. nudum populations, the latter being ecologically more diverse and geographically or hydrographically more isolated. The proportion of polymorphic loci per population ranged from 0.25 to 0.36. Heterozygote deficiencies were observed at two acid phosphatase loci in offshore populations of E. nudum which showed a propensity for vegetative reproduction.