Comparative floral anatomy and evolutionary interpretations of cryptic dioecy in Ocotea velloziana (Lauraceae)

Abstract

Ocotea velloziana (Lauraceae) is a species with cryptic dioecy. The staminate flowers of this species have a pistillode and pistillate flowers have staminodes, which often makes it difficult to describe circumscribe the reproductive system correctly. Therefore, to understand the evolution of dioecy in this species, the morphology of both floral morphotypes needs to be described. We apply traditional and modern approaches to describe the comparative floral anatomy of the two floral morphotypes in O. velloziana. We found that the pistillate flowers have fewer (three) vascular traces in the tepals (compared to five traces in the tepals of the staminate flowers). The pistillode and the staminodes in the flowers of O. velloziana are smaller and less vascularized than their homologous, fertile counterparts, the pistils and stamens. In addition, even though the nectaries are smaller in pistillate flowers, their basic morphology and vascularization are similar in the two floral morphotypes. Our results suggest androtepaly in O. velloziana, however future ontogenetic studies and investigation of the vascularization are necessary in other Lauraceae species to clarify this issue. The nectaries have originated from the hypanthium and may be characterized as nectar-secreting emergencies not homologous to the stamens.

Key words:
dicliny; floral vascularization; histochemistry; nectaries; perianth