Incompatibility inCordia alliodora(Boraginaceae), a neotropical tree

Abstract

Incompatibility and variation in floral morphology in Cordia alliodora (R. & P.) Oken (Boraginaceae) were investigated using a combination of fieldwork and light and ultraviolet microscopy. Results from controlled crosses clearly showed the presence of two groups of trees, where intergroup crosses were compatible but intragroup crosses were incompatible. A sporophytic, diallelic, one-locus incompatibility system was inferred. Limited failure of the incompatibility mechanism was found (approximately 1% of crosses) for both selfs and intragroup crosses. Whereas most authors previously described C. alliodora as a homostyle, measurement of floral traits and study of their relationship to controlled crosses revealed a poorly defined variation in stigma size strongly associated with the incompatibility groups. The relatively undeveloped heteromorphy, coupled with a strong incompatibility mechanism, is of particular interest. The genus Cordia, in particular the Cerdanae, appears to offer fruitful ground for further investigation into aspects of the evolution and development of heterostyly. Key words: incompatibility, heterostyly, Cordia alliodora.