Pollination in Turnera subulata (Turneraceae): Unilateral reproductive dependence of the narrowly oligolectic bee Protomeliturga turnerae (Hymenoptera, Andrenidae)

Turnera subulata Smith (Turneraceae) is a subshrub with distylic flowers, common as a ruderal plant in NE-Brazil. We studied the pollination biology of a population in João Pessoa, Paraíba, paying attention to effective pollinators and characteristics of short- and long-style morphs. The flowers attracted insects of 28 species, predominantely bees. Several bee species were observed to be effective pollinators, including highly eusocial species, polylectic solitary species (Centris and Xylocopa) and 1 oligolectic species, Protomeliturga turnerae (Andrenidae, Panurginae). The latter species shows reproductive dependency on T. subulata. The plant species, on the other hand, does not depend on this specialized bee, as reproductive success was also guaranteed by the other polylectic flower visitors. Floral characteristics of both floral morphs are discussed with respect to pollination biology.