Abstract
Geographic variation in pollination ecology is poorly documented, if at all, in many plant-pollinator systems. Great insights could be gained into the abiotic and biotic factors which impact the evolution of floral properties and their potential to lead to speciation by doing so, as both can vary naturally over the geographic range of a plant species. We characterized the pollination ecology of the Andean tree Oreocallis grandiflora (Family: Proteaceae) at the northern and southern ends of its range in Ecuador and Peru in terms of flower morphology, nectar properties, pollinators and plant reproduction. We found significant divergence in the two populations in terms of style length and flower openness, nectar standing crop and secretion rate, and pollinator community. We did not find a significant difference in the length of the pollen presenter or in nectar sucrose concentration by weight (% Brix). The observed divergence in floral traits between the two study populations may be related to a combination of factors, including genetic drift and isolation by distance, distinctive suites of pollinators, or heterospecific pollen competition, which future studies should further investigate. This study demonstrates that pollination ecology can vary substantially across the geographic range of a species, with implications for delimiting species and subspecific taxa.
Highlights
The study of pollination ecology has played an important role in our current understanding of co-evolution (Cook & Rasplus 2003) and speciation (Kay & Sargent 2009), and provides important baseline information to inform practical ecosystem-level conservation efforts (Pauw 2007) in a time of pollinator declines (Biesmeijer et al 2006)
Ecuadorian flower morphology was characterized by longer style length (SL) and the minimum straight-line distance between the pollen presenter and the intersection of the petals and the style (PED), and a wider angle of openness (AO), while Peruvian flowers were characterized by shorter SL and PED with a smaller AO (Tab. 1)
We found that the pollination ecology of Oreocallis grandiflora fit generally within what has been reported in other members of the Proteaceae, though it is of note that autogamous selfing was possible
Summary
The study of pollination ecology has played an important role in our current understanding of co-evolution (Cook & Rasplus 2003) and speciation (Kay & Sargent 2009), and provides important baseline information to inform practical ecosystem-level conservation efforts (Pauw 2007) in a time of pollinator declines (Biesmeijer et al 2006). Intraspecific variation in floral morphology and pollination ecology may arise through several mechanisms, primarily genetic drift, abiotic selection, and biotic selection driven by pollinators, herbivores, and competing plant species. Environmental factors such as temperature and HAZLEHURST ET AL
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