Variation of floral traits across a geographical framework of pollinator assemblages differing in functional, morphological and ethological features.

SÉRSIC ALICIA; BARANZELLI MATIAS; COSACOV ANDREA; FERREIRO GABRIELA; PAIARO VALERIA; COCUCCI ANDREA

Drakensberg

Congreso; XXXIX Annual Conference of South African Association of Botanists; 2013

The study of geographical variation of phenotypic floral traits provides a suitable background to understand the role of pollinator assemblages as drivers of floral diversity patterns. Here we present three plant pollinator systems that differ in pollinator assemblages features. Monttea aphylla (Plantaginaceae), a widespread species of the Monte desert, offers simultaneously oils and nectar as rewards to functionally diverse pollinator assemblages. Results of variation in floral rewards as a response to those assemblages, as well as to other biotic and abiotic factors at a geographical scale suggest that investment in the more expensive reward (oil) is promoted in communities where nectar foragers other than oil collecting bees are more abundant and where plants presumably more strongly compete for the services of the more specialized pollinator. In communities where the specialized pollinator is the only available, competition should be relaxed because investment in the more expensive reward would not be compensated with better services of pollinators. Calceolaria polyrhiza (Calceolariaceae) is widely distributed in the arid Patagonian steppe and in the understory of temperate forests. Pollinators are either of two community-specific oil-collecting bees which strongly differ in size. Through floral integration analyses and covariation patterns we observed that plant-pollinator phenotypic matching across the geographical range is facilitated through variation in mechanical-fit related traits and their decoupling from variations on attraction-related traits, which include corolla size. Finally, phenotypic selection in the finch pollinated Patagonian bush Anarthrophyllum desideratum (Fabaceae) showed that variation in floral traits was only partially explained by assemblages shifts; one species, Zonotrichia capensis, is dominant in most populations and seems to be locally idiosyncratic in the way they handle flowers in order to access nectar and consequently carry pollen on different parts of the head. Both, changes in pollinator assemblages and behavior across populations appear to account, at least in part, for the geographical variation in flower phenotype.