PHYLOGENETIC ANALYSIS OF PINES USING RIBOSOMAL DNA RESTRICTION-FRAGMENT-LENGTH-POLYMORPHISMS

Phylogenetic relationships among 30 species of the genus Pinus were st udied using restriction site polymorphism in the large subunit of nucl ear rDNA. Of the 58 restriction sites scored, 48 were phylogenetically informative, and the 30 species reduced to ten taxa when species with identical restriction site patterns were combined. These ten taxa cor responded to the currently recognized subsections of the genus, with t he sole exception of P. leiophylla, which was identical in its pattern of restriction sites to all three species included from subsect. Ooca rpae despite its being in a different section of subg. Pinus (Pinea in stead of Pinus). A measure of the proportion of phylogenetic informati on contained within the data set (Homoplasy Excess Ratio, or HER) reve aled that the character states were significantly non-randomly distrib uted among the ten taxa (HER = 0.71. p < 0.01). Branch-and-bound searc hes using either Wagner or Dollo parsimony as the optimization criteri on were carried out using PAUP in order to estimate phylogenetic relat ionships among the ten taxa. Three taxa (Picea pungens, Tsuga canadens is, and Larix decidua) were used independently as outgroups for purpos es of rooting the trees. Despite the extreme differences in the assump tions underlying the Wagner and Dollo parsimony, the two gave surprisi ngly similar estimates of phylogeny, with both analyses supporting the monophyly of the two major subgenera Pinus and Strobus and differing in topology only in the placement of subsect. Ponderosae within subg. Pinus. The likelihood for the Wagner tree was only slightly higher tha n that computed for the Dollo tree.