Diversity and evolution of the association of oil-collecting bees with Nierembergia (Solanaceae) and Calceolaria (Calceolariaceae).

COCUCCI A.A.; SÉRSIC A. N.; COSACOV A.

Congreso; Conference ATBC-gtoe: Impacts of Global Change on Tropical Ecosystems.; 2009

Society for Tropical Ecology

Recent molecular phylogenies let us draw conclusions on the origin and diversification patterns of these two genera which are among the most specious clades of plants bearing oil-flowers in temperate South America. In both genera the acquisition of elaiophores, traceable back to the earliest ancestors, and represent key innovations associated with strong speciation relative to sister genera. Elaiophores have been co-opted for pollination service from trichomes of vegetative organs or petals outside, where they are involved in other functions, e.g. herbivores deterrent. Extrafloral oil-collection further suggests a non nuptial origin of the oil-based association. In Nierembergia, the transition oil-flowers involved the loss of nectaries and the exaptation of corolla tube from a nectar container to an exposition organ. Primary association was probably with Centridines in Calceolaria or with smaller Tapinotaspidines in Nierembergia. Shifts from large to small oil-collecting bees (Calceolaria) and vise versa (Nierembergia) have occurred. In both genera studies on multiple populations show that in a single species the locally predominant oil-bees changes between Centridines and Tapinotaspidines, suggesting that these shifts may still be occurring. Elaiophore loss is linked to shifts in pollination modes, i.e. to habitual autogamy, pollination by pollen collecting bees or pollination by non nectarivorous birds. In Calceolaria shifts in pollination modes seems to be associated with colonization of new geographic areas, such as those located northern of the Huancabamba Deflection.