PHYLOGENY, BIOGEOGRAPHY, AND SYSTEMATICS OF THE WAHLENBERGIA-FERNANDEZIANA COMPLEX (CAMPANULACEAE, CAMPANULOIDEAE)

Monophyly of the populations of Wahlenbergia (Campanulaceae: Campanulo ideae) in the Juan Fernandez Islands is supported by chromosome number (n = 11 in a genus that otherwise has x = 8 or 9), data on allozyme v ariation, and morphology. Cluster analyses of 41 morphological charact ers in 23 specimens, using average taxonomic distance, Euclidean dista nce, and product-moment correlation as coefficients of resemblance, su pport recognition of five species. Populations on Masatierra comprise three species: W. berteroi (which also occurs on nearby Santa Clara), W. fernandeziana, and W. grahamiae; recognition of W. larrainii as dis tinct from W. fernandeziana is not supported. Populations on Masafuera , heated as a single species by all previous authors, are divisible in to two species: W. masafuerae, growing on the coast, and W. tuberosa, growing inland. Phylogenetic analyses of 21 morphological characters f or the five species generate three equally parsimonious trees of 28 st eps with a consistency index of 1.000. In the preferred tree, which pa rallels the structure of the dendrogram based on product-moment correl ation, the complex is divided into two clades: the non-cormose clade, defined by an increased number of teeth on the leaf margin and glabrou s filaments (W. fernandeziana and W. grahamiae), and the cormose clade , defined by the presence of a subterranean or epigeous woody caudex, linear leaves with revolute margins and the adaxial surface glabrous, narrow bracts, and narrow corolla lobes (W. tuberosa, W. masafuerae, a nd W. berteroi). It is inferred that the complex originated on the geo logically older island of Masatierra, giving rise there to the non-cor mose clade. It then dispersed to the younger island of Masafuera where it gave rise to the cormose clade, one branch of which (W. berteroi) resulted from dispersal back onto the older island. This pattern of cl adogenesis on the secondary island and back-dispersal to the primary i s unique among genera that have speciated in the archipelago.