Aspects of the breeding strategies of two species of Senna (K. Bauhin) P.Mill. (Caesalpiniaceae) co-occurrent in a continental sand dune ecosystem from the Medium São Francisco River, Bahia

Abstract

The flower visitors and the co-existence strategies of Senna gardneri (Benth.)H.S.Irwin & Barneby and Senna macranthera var. pudibunda (Benth.)H.S.Irwin & Barneby, two sympatric species from the continental sand dunes of middle São Francisco River, Bahia (10º47’37’’S, 42º49’25”W), were investigated from February to December 2000. These species have blossoms with hermaphrodite yellow flowers, poricide anthers and produce pollen as the sole reward to the visitors. Senna gardneri produced most of the flowers at the end of the rainy season and S. macranthera var. pudibunda at the beginning of the dry season. Senna gardneri was visited by 13 bee species (n=227) with Trigona spinipes (Fabricius, 1793) (55.5%), Frieseomelitta silvestrii languida (Moure, 1989) (12.7%), and Xylocopa grisescens Lepeletier, 1841 (7.9%) as the most abundant species. Senna macranthera var. pudibunda received visits of 14 species (n=178) with predominance of T. spinipes (40%), Augocloropsis calicroa Cockerell, 1900 (27%), and F. s. languida (15.8%). The temporal separation in the flowering period between Senna species, the great quantity of flowers produced from these species and the low similarity of the flower visitors attracted to them seems to be the factors responsable for the co-occurance of Senna species in that area.