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Phylogeny, Biogeography, and Systematics of the Wahlenbergia fernandeziana Complex (Campanulaceae: Campanuloideae)

1996; American Society of Plant Taxonomists; Volume: 21; Issue: 3 Linguagem: Inglês

10.2307/2419667

1548-2324

Thomas G. Lammers,

Plant and animal studies

Monophyly of the populations of Wahlenbergia (Campanulaceae: Campanuloideae) 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 variation, and morphology. Cluster analyses of 41 morphological characters in 23 specimens, using average taxonomic distance, Euclidean distance, and product-moment correlation as coefficients of resemblance, support 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 distinct from W. fernandeziana is not supported. Populations on Masafuera, treated as a single species by all previous authors, are divisible into two species: W. masafuerae, growing on the coast, and W. tuberosa, growing inland. Phylogenetic analyses of 21 morphological characters for the five species generate three equally parsimonious trees of 28 steps with a consistency index of 1.000. In the preferred tree, which parallels the structure of the dendrogram based on product-moment correlation, the complex is divided into two clades: the non-cormose clade, defined by an increased number of teeth on the leaf margin and glabrous 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, and W. berteroi). It is inferred that the complex originated on the geologically older island of Masatierra, giving rise there to the non-cormose 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 cladogenesis on the secondary island and back-dispersal to the primary is unique among genera that have speciated in the archipelago. The Juan Fernandez Islands are situated in the southeastern Pacific Ocean and comprise three islands (Table 1): Masatierra, which lies 650 km west of continental Chile; Santa Clara, to the southwest of Masatierra and separated from it by a 1 km wide channel; and Masafuera, which lies 145 km farther west. All three are of volcanic origin and have never been connected to the South American mainland. The archipelago belongs to the Republic of Chile and for administrative purposes forms part of Provincia de Valparaiso within that country's V