The maritime species of Abronia (Nyctaginaceae)

Abstract

An analysis of the variation patterns in the three Pacific Coast maritime species ofAbronia (Nyctaginaceae) based on 95 population studies, is presented in the form of scatter diagrams. The relationship of this group of species to other members of the genus, such asA. gracilis Benth., is considered. Despite widespread evidence of hybridization and introgression, the three maritime species (A. latifolia Eschsch.,A. maritima Nutt. ex S. Wats., andA. umbellata Lam.) maintain their distinctness. Most of the taxonomic segregants in this group have been based on what appear to be hybrid or introgressed individuals, many of which closely resemble members of a series of artificial hybrids made in the greenhouse. The chromosome number of all three species is estimated as 2n = ca. 46. The species are shown to differ markedly in ecological preference:A. latifolia competing successfully on stable areas of dunes from Vancouver Island, British Columbia, to Santa Barbara Co., California;A. maritima being the major foredune former along the strand from San Luis Obispo Co., California, south to Nayarit, Mexico; andA. umbellata occurring on more stable dunes from San Luis Obispo to San Diego Co., California, and sporadically north and south of this area. The latter species is pollinated chiefly by nocturnal insects and is fragrant in the evening, whereas the other two have diurnal flowers. One widespread and two rarer, more northern subspecies ofA. umbellata are recognized in the taxonomic revision, while the other two species are not subdivided taxonomically.