The classification of dwarf mistletoes (Arceuthobium spp., Viscaceae) in section Campylopoda, series Campylopoda

Abstract

The taxonomic classification of dwarf mistletoes (Arceuthobium spp., Viscaceae) is complicated due to their reduced morphology, requiring the integration of not only morphology but also phenology, geography, and host relationships. This has been particularly true for the classification of taxa in subgenus Vaginata, section Campylopoda, series Campylopoda. Most of the species in this group have been recently circumscribed in synonymy with or reduced to subspecies of Arceuthobium campylopodum Engelm; however, we contend they deserve separate species recognition. To address this question, we have conducted morphological analyses of the taxa in ser. Campylopoda using univariate and multivariate statistical analyses. Our results have demonstrated that these taxa can be determined to species using morphological data without consideration of geographic location or host specificity; however, the host specialization and geographic distribution exhibited by these taxa also supports their classification as species. Here, we discuss the evidence supporting the specific classification of ser. Campylopoda taxa. This taxonomic framework permits the treatment of several dwarf mistletoe populations with geographically restricted distributions, fewer morphological differences, and specialized host affinities as subspecies of Arceuthobium abietinum (Engelm.) Abrams, Arceuthobium microcarpum (Engelm.) Hawksw. & Wiens, and Arceuthobium tsugense (Rosend.) G.N.Jones. It is also the most practical classification for the management of these economically and ecologically important parasitic plants.