A PHYLOGENETIC ANALYSIS OF SCHIEDEA AND ALSINIDENDRON (CARYOPHYLLACEAE, ALSINOIDEAE) - IMPLICATIONS FOR THE EVOLUTION OF BREEDING SYSTEMS

Phylogenetic analysis of Schiedea and Alsinidendron (Caryophyllaceae), a monophyletic lineage endemic to the Hawaiian Islands, produced six equally most parsimonious trees with 132 steps using morphological characters. Four major clades were found in all trees. Breeding system characters were excluded from the analysis because of the likelihood that dimorphism (gynodioecy, subdioecy, dioecy) has evolved in parallel in Schieden, although subsequent inclusion of these characters had little effect on topology. Dimorphism is found in the two clades occurring primarily in dry habitats. Mapping of breeding systems on the phylogeny suggests that dimorphism has probably evolved on two or more occasions, depending on the number of character states and whether the character is treated as ordered or unordered. One to several reversals from dimorphism to hermaphroditism have also occurred. Dimorphic species occur only in dry habitats, but mapping of habitat on the phylogeny suggests that hermaphroditic species originally may have invaded dry habitats without evolving a dimorphic breeding system. Ecological shifts to very wet habitats appear to have favored the evolution of autogamy, which has occurred independently in the two clades largely restricted to mesic or wet habitats. The striking variation in breeding systems found in Schiedea and Alsinidendron appears to result in large part from the invasion of diverse habitats in the Hawaiian Islands following colonization by the ancestor of this lineage.