Cleome spinosa (Capparaceae): polygamodioecy and pollination by bats in urban and Caatinga areas, northeastern Brazil
Machado, Isabel; Cristina Lopes, Ariadna; Valentina Leite, Ana; Virgíniade Brito Neves, Cleci
published: Dec 19, 2006
The mainly tropical and subtropical family Capparaceae has many species pollinated by bats and/or sphingids. Here we report data on the pollination ecology and reproductive biology of Cleome spinosa Jacq. occurring in natural populations in urban and Caatinga areas in northeastern Brazil. The species is an annual polygamodioecious herb exhibiting three floral types: pistillate, staminate and hermaphrodite flowers. Trimonoecious, andromonoecious, and pistillate individuals occur in both urban and Caatinga populations. Inflorescences produce on average 37.6 ± 6.82 (mean ± s.d.) flowers with 3.46 ± 0.91 open flowers per day. Anthesis is crepuscular. The flowers are pollinated by glossophagine (Glossophaga soricina) and phyllostomine (Phyllostomus discolor) bats. Sphingids also visit the flowers but act as nectar thieves only. Nectar production is continuous from 5:30 p.m. to 1:30-2:30 a.m. and the nectar accumulates as a drop at the base of the stamens. The total volume secreted by a flower per night is 116.9 ± 25.95 μl, with 23.38 ± 20.22 μl being produced every two hours (n=10), thus totaling five or six drops per flower/night. In that way, one inflorescence produces ca. 348 μl nectar/night, totalling 16,008 μl nectar per individual/night. Sugar concentration in the nectar is 15.56 % ± 4.75 (n=24). After removal by a pollinator, a new nectar drop takes 15-20 minutes to be formed. Pollen-ovule ratio of hermaphrodite flowers is high (1,282.6), suggesting obligatory xenogamy. However, C. spinosa is self-compatible with high fruit and seed set in all controlled pollination treatments. The flowers of C. spinosa have attributes that fit in both sphingophily and chiropterophily syndromes, and may represent an example of a sphingid-bat transition species. However, at least in the studied populations, only bats acted as pollinators, maintaining a high natural fruit and seed set.