DISTYLY IN OREOCARYA CRASSIPES (BORAGINACEAE), AN ENDANGERED PLANT SPECIES

Abstract

Oreocarya crassipes, an endangered angiosperm native to the Trans-Pecos region in southern Brewster County, Texas, exhibits distyly, a breeding system that includes two floral morphs with reciprocal positioning of the anthers and stigmas. The long-style (LS) morph has stigmas above the anthers, and the short-style (SS) morph produces anthers above the stigmas. In the present study, multiple aspects of distyly were examined across four populations of O. crassipes including morph ratios, variation in floral morphology, and patterns of macroscopic and microscopic floral development of the morphs. Morph ratios vary among populations, but for all of the samples pooled the ratio was 1 LS:1 SS. Distyly was observed to be well established in the species, with stigma height, anther height, and stigma-anther separation significantly different between the two morphs. Floral developmental patterns are similar to those in related species, suggesting a conserved and similarly co-opted developmental pathway for the origin of distyly in the genus and relatives.