XVI International Botanical Congess

Using habit combined with anatomical characters, particularly the ontogeny, size, and shape of utricles, we have been able to delineate ten distinctive species of Codium from the Pacific coast of Mexico and seven from the Atlantic and Caribbean coasts. Among these distinctive species are four that were previously undescribed. In the Gulf of California, there are numerous populations that exhibit a bewildering array of variability which has led to the description by earlier workers of 12 species. Using multivariate analysis and sequence comparison of the 16S gene from mitochondrial rDNA, we were able to recognize three clusters among the 12 species, each cluster representing a complex species. The total of 13 Pacific species makes this region one of four centers of Codium diversity, being exceeded only by southern Australia, southern Africa, and Japan.