Phylogenetic Relationships within Apocynaceae s.l. Based on trnL Intron and trnL-F Spacer Sequences and Propagule Characters

Abstract

Relationships within Apocynaceae s.l. (Apocynaceae s. str., Periplocaceae, and Asclepiadaceae) were investigated by maximum parsimony analysis of morphological and molecular sequence data. Sequences of the plastid trnL intron and trnL-F spacer for 152 accessions for representatives of all major tribes were included in this study; 96% of these sequences represent new data. Two outgroups were selected from the closely related Loganiaceae. The total evidence matrix incorporated trnL intron and trnL-F spacer sequences, insertion/deletion information, and propagule characters. The phylogenetic hypothesis derived from this data set was used to evaluate the most current classification systems and was also used to investigate trends in seed dispersal. Apocynaceae s.l. are a strongly defined monophyletic group, a finding that should be reflected in taxonomic treatments. The recognition of three of the five subfamilies proposed by Endress and Bruyns in 2000 is supported by the monophyletic Periplocoideae, Secamonoideae, and Asclepiadoideae, whereas the paraphyletic Rauvolfioideae and Apocynoideae are not supported. The precise position of the Periplocoideae, however, remains unclear. Traditional tribal delimitations were less congruent with our total evidence phylogeny. The evolution of seed comas and enhanced long-distance dispersal within the Apocynaceae s.l. probably contributed to accelerated cladogenesis, ultimately giving rise to the majority of the extant genera within the family. Phylogeographic analysis of our data provides some evidence for a Gondwanan origin of the family.