Relationships of the genus Azorella (Apiaceae) and other hydrocotyloids inferred from sequence variation in three plastid markers

Relationships of genera traditionally referred to the subfamily Hydrocotyloideae (Apiaceae), with emphasis on Azorella, were estimated using sequence variation in the markers matK, rbcL, and rps16. The analyses were based on a combined dataset comprising 66 taxa represented by 134 sequences (29 matK, 40 rbcL, and 65 rps16) as well as partial datasets constructed from individual markers and combinations of them. The results confirm previous observations that the hydrocotyloids are an unnatural assemblage of taxa from at least four different groups, of which one belongs to Araliaceae and the remaining ones to Apiaceae. The recently recognized subfamilies Mackinlayoideae and Azorelloideae are supported, with the possible exclusion of Platysace from the former and the addition of Asteriscium, Diposis, Domeykoa, Drusa, Homalocarpus, Laretia, Oschatzia, and Pozoa to the latter. Within Azorelloideae, the Azorella, Bowlesia, and Asteriscium clades are identified, although relationships among them are obscure. The genus Azorella occurs in two subclades that also include other genera, and is obviously paraphyletic as presently conceived. The Azorella sections Cirrhosae and Ciliatae are probably also paraphyletic.