Variación interespecífica de ensambles de polinizadores en Nierembergia (Solanaceae) en relación con la localización geográfica y la variación fenotípica de las flores

Abstract

Understanding how the interactions of related plant species with pollinators vary on a spatial scale provides the opportunity to establish links between macroevolutionary patterns and microevolutionary processes, as well as to approach the mechanisms underlying plant diversification. In this work, we explore the variation in pollinator assemblages of 15 species and varieties of Nierembergia (Solanaceae) across the distribution range of the genus in Argentina, in relation to variation in floral phenotype and geographic location. By field observations, morphometric measurements of flowers and comparative phylogenetic methods, pollinator assemblages and flowers of Nierembergia taxa were characterized and compared, and the association between pollinator assemblage composition, geographic location, floral morphology and phylogenetic relationships was evaluated. 13 species of oil-collecting bees were recorded as pollinators. The assemblage composition was strongly associated with geographic location, that is, Nierembergia taxa in nearby areas had greater similarity in their pollinator assemblages than geographically distant taxa. This pattern was not associated with phylogenetic relationships among taxa, except for a group of high mountain species in northwestern Argentina. On the other hand, interspecific variation was found in the floral phenotype, mainly in the corolla and the oil-producing gland size. However, Nierembergia taxa with similar floral phenotypes did not share the composition of the pollinator assemblage, as expected. In conclusion, we found a mixed macroevolutionary pattern in which some phylogenetically distant Nierembergia taxa converge geographically in the composition of pollinator assemblages, while this attribute is conserved in a phylogenetic clade. This pattern suggests that the role of pollinators in Nierembergia diversification is more complex than previously thought.