Phenotypic Variation, Distribution and Relationships of Diploid and Tetraploid Populations of the Claytonia perfoliata Complex (Portulacaceae)

Abstract

Chromosome counts from 235 populations of Claytonia (Montia) perfo- liata (sensu lato) reveal a polyploid pillar complex based on three morphologically different and geographically defined diploids. Claytonia perfoliata Willdenow with linear juvenile leaves and deltoid (mucronate) mature basal leaves ranges south- eastward from the Coast Ranges of California, through the Sonoran Desert Ranges of Arizona, to high elevation coniferous forests of Mexico and Guatemala. In con- trast, diploid C. rubra (Howell) Tidestrom generally occurs in drier montane and transmontane coniferous woodlands of the Sierra Nevada and Cascade Ranges. It has basal leaves that vary ontogenetically from rhombic to deltoid (obtuse). Diploid C. parv-flora Hooker is Sierra Nevadan and its juvenile and mature basal leaves are all linear. A fourth entity in this species complex, C. perfoliata ssp. viridis (Davidson) Fellows, contributes to variation at the tetraploid level but has not yet been found as a diploid. Progeny of field collected tetraploids resembling C. perfoliata and C. rubra diploids were grown under uniform regimes of light, temperature, and mois- ture for comparison with their diploid counterparts. Each family of progeny was indistinguishable from its parent, implying a high degree of self-fertilization in nat- ure. Comparisons of pollen-ovule ratios and observations of flower structure indicate that diploid C. parv flora is facultatively xenogamous while the other two diploid species are prevailingly autogamous. The distribution of tetraploids tends to parallel that of their diploid morphological counterparts. The often discontinuous variability found in natural populations of this species complex can be ascribed in part to sympatry of autogamous heteroploid biotypes. Environmentally induced variation is an additional complicating factor in the morphological analysis of mixed popu- lations. The developmental sequence of basal leaf shapes is genotypically deter- mined, but plants in unfavorable habitats may flower prematurely and thus differ from their siblings in the taxonomically important trait of leaf shape.