Systematics of the Lyonia Group (Andromedeae, Ericaceae) and the Use of Species as Terminals in Higher-Level Cladistic Analyses

Abstract

Phylogenetic relationships within the Lyonia group of the Andromedeae, i.e., Agarista, Craibio- dendron, Lyonia, and Pieris, are investigated by means of cladistic analyses of morphological (external morphology, anatomy, embryology) and molecular (matK nucleotide sequences) characters. Analysis of morphological characters used species as terminals and sections or genera as terminals in two separate matrices. Combined analyses used matK with each of these morphological matrices. Results of all analyses were completely congruent in regards to generic circumscription, but relationships among genera were unresolved in morphological analyses and only weakly supported in molecular analyses. The monophyly of the Lyonia group and each of its genera was supported. Molecular and combined analyses support the hypothesis that Agarista and Pieris are sister, but differ in the placement of Craibiodendron. Both morphological and molecular analyses support the hypothesis that the lepidote species of Lyonia, i.e., sect. Lyonia, constitute the sister group to the remaining members of this genus. Both also support the sister group relationship of Lyonia sect. Pieridopsis, an eastern Asian group, and Lyonia ligustrina, the sole representative of sect. Arsenococcus, a species of eastern North America. Finally, both molecular and morphological analyses support placement of Pieris subg. Arcterica, i.e., P. nana, as sister to Pieris subg. Pieris. Based on this study of generic relationships within the Lyonia group, the use of species as terminals is recommended for cladistic analyses of supraspecific relationships.