A Phylogenetic Analysis of Salix (Salicaceae) Based on matK and Ribosomal DNA Sequence Data

Abstract

The genus Salix has proven a fertile taxon for a host of evolutionary and ecological studies, yet much work remains in the development of a definitive phylogenetic context for those studies. We performed phylogenetic analyses, using both maximum likelihood and maximum parsimony techniques, of chloroplast-encoded matK and nuclear-encoded ribosomal DNA (rDNA) gene sequences, gathered from specimens deemed representative of the existing subgeneric classification, with the objective of identifying and elaborating the phylogenetic relationships within Salix . Comparisons between the two phylogenetic hypotheses indicate a high degree of polyphyly in the matK -based phylogeny. This we attribute to the effects of hybridization, introgression, and lineage sorting. Comparisons with previous molecule-based phylogenetic hypotheses indicate a fair degree of congruence and all are unanimous in placing Chosenia arbutifolia within the genus Salix . The phylogenetic analysis of our ITS data set has produced results that generally support the most-recent infrageneric classification.