HIGHER-LEVEL RELATIONSHIPS OF APIALES (APIACEAE AND ARALIACEAE) BASEDON PHYLOGENETIC ANALYSIS OF RBCL SEQUENCES

The two families of the order Apiales (Apiaceae and Araliaceae) repres ent a classic example of the difficulty in understanding evolutionary relationships between tropical-temperate family pairs. In Apiales, thi s problem is further compounded by phylogenetic confusion at almost ev ery taxonomic level, including ordinal, interfamilial, and infrafamili al, due largely to difficulties in understanding trends in morphologic al evolution. Phylogenetic analyses of rbcL sequences were employed to resolve relationships at the ordinal and familial levels. The results of the ordinal analysis confirm the placement of Apiales in an expand ed subclass Asteridae as the sister group to Pittosporaceae, and refut e the traditional alliance of Apiales with Cornales and Rosidae. This study has also resolved relationships of a number of enigmatic genera, suggesting, for example, that Melanophylla, Aralidium, Griselinia, an d Toricellia are close relatives of Apiales. Clarification of phylogen etic relationships has concomitantly provided insights into trends of morphological evolution, and suggests that the ancestral apialean taxo n was probably bicarpellate, simple-leaved, woody, and paleotropical. Phylogenetic analysis at the family level suggests that apiaceous subf amily Hydrocotyloideae, often envisioned as an intermediate group betw een Apiaceae and Araliaceae, is polyphyletic, with some hydrocotyloids closely allied with Araliaceae rather than Apiaceae. With the excepti on of some hydrocotyloids, Apiaceae appear to be monophyletic. The rel ationship between Apiaceae and Araliaceae remains problematic. Althoug h the shortest rbcL trees suggest that Apiaceae are derived from withi n a paraphyletic Araliaceae, this result is only weakly supported.