A Morphometric Analysis and Taxonomic Appraisal of the Hawaiian Silversword Argyroxiphium sandwicense DC. (Asteraceae)

Abstract

Morphometric techniques were used to examine the pattern of variation of45 characters between the Haleakala and Mauna Kea populations of Argyro xiphium sandwicense. Qualitative features were also evaluated. A framework for a priori comparisons between the two populations of A. sandwicense was provided by including two additional species in the study, that is, A . kauense and .A. virescens var. paludosa. The F tests of one-way analysis of variance indicate that the means of each of 18 characters differ significantly (P ~ 0.05) between the two populations of A. sandwicense. Based on the presence of quantitative differentiation and geographical isolation and the near absence of qualitative differentiation between the two populations, it is proposed to recognize them as two different subspecies: A. sandwicense ssp. macrocephalum (Haleakala) and A. sandwicense ssp. sandwicense (Mauna Kea). The stud y also indicates that A . virescens var. paludosa, A . kauense, and A . sandwicense are distinct from one another in several quantitative and qualitative characters. Taxonomically useful quantitative characters include inflorescence proportions, leaf proportions, number of ray florets per capitulum, and capitulum diameter. The subspecies of A . sandwicense can be recognized on the basis of inflorescence proportions. However, to separate all four taxa, based on quantitative characters, a combination of at least three of the foregoing features appear to be needed . A taxonomic key and descriptions for common taxa ofArgyro xiphium of the island of Hawai'i and of East Maui are presented.