Utility of Ontogenetic and Conventional Characters in Determining Phylogenetic Relationships of Saururaceae and Piperaceae (Piperales)

Abstract

Morphological and developmental evidence is utilized in a phylogenetic analysis of Piperales. Best resolution of trees was obtained by combining ontogenetic data with conventional morphological data. Floral ontogeny provides a means to determine homology among character states as well as to provide additional characters not observable in mature flowers. Both Lundberg and outgroup rooting were performed using a hypothetical ancestor defined by general ontogenetic states in the former and by five taxa presumably related to the ingroup in the latter. Polarization of character states via ontogenetic generality principles is congruent with outgroup polarization. Saururaceae and Piperaceae are each monophyletic. Saururaceae are supported by three synapomorphies, with Saururus as the basal taxon. The other three saururaceous genera (Anemopsis, Houttuynia, Gymnotheca) share the derived character slates of syncarpy, stamen-carpel adnation, and an inferior or half-inferior ovary. Piperaceae are supported by seven synapomorphies with Zippelia as the basal taxon. Six other synapomorphies unite the remaining Piperaceae suggesting that Macropiper and Pothomorphe are specialized offshoots of the morphologically variable Piper. Numerous autapomorphies support Peperomia as a distinct and specialized offshoot within Piperaceae. Within the sister clades Saururaceae and Piperaceae, there are parallel reduction trends in floral organ number and in the sequence of floral organ initiation.