STUDIES ON THE EVOLUTION OF KECKIELLA (SCROPHULARIACEAE)

Keckiella Straw (Scrophulariaceae) is a genus native to the California Floristic Province and the adjacent deserts. The seven species (which comprise eleven taxa) have radiated into most of the chaparral, sage scrub, and related ecotonal plant communities of the region. Although all species are facultatively drought-deciduous, the genus presents a wealth of vegetative and floral diversity. These dissertation studies address the systematic wood and leaf anatomy of Keckiella, the species pollination biology, and the correlations of pollinator-type with nectary anatomy.; These studies are an attempt to place particular anatomical characteristics in an ecological context. The study of ecological correlations of wood and leaf anatomy is published as: Michener, D. C. 1981 Aliso 10:39-57 and is presented as the first chapter. The linked studies of pollination biology and the correlations with nectary anatomy are based on the premise that pollinators are important selective agents affecting structural diversification in nectary anatomy. The pollination study establishes that four of the species are pollinated by a diverse array of pollen- and nectar-foraging bees, while the other species are hummingbird-pollinated. Nectar is shown to be the primary attractant in all seven species. The ongoing study of nectary anatomy in relation to nectars and pollinator type indicates that, in Keckiella, the ornithophilous species and the one large-flowered bee-pollinated species all have large nectar fluxes and nectaries. Quantification of the relationships of nectary phloem vascularization to nectar sugar-concentration and nectar secretion is based on a data base that is difficult to acquire. This line of inquiry is being persued. It is clear that nectar secretion is better correlated with nectary surface area than with nectary volume.; Keckiella is closely related to Penstemon; the genera differ primarily by nectary type. The epistaminal nectary of Penstemon is a novel structure. I suggest that this nectary type reduces the structural linkage between nectary size (nectar flux) and capsule size (seed production). Hummingbird-pollination is a derived pollination type in both genera.