Pollen deposition patterns onto the pollinators’ body in sphingophilous communities of subtropical Argentina

Abstract

Plant species that coexist and share pollinators may experience inter-specific competition for pollinator service or interference of improper pollen. To avoid the latter, plant species may use different areas of the pollinators´ body to deposit their pollen, either by different floral architectures or by different floral lengths. We evaluate here the existence of this pattern of differential use of body areas of pollinators in 33 sphingophilous communities of subtropical Argentina. We use null models to evaluate if the plants deposit the pollen overdispersed relative to what would be expected by chance either in different body parts or at different heights in the proboscis of hawkmoth pollinators. We found that 42 native plants species are pollinated by hawkmoths in subtropical Argentina. We observed a significant and positive correlation between the operative length –i.e. the distance between anthers and stigma from nectar– of the flowers and the mean length of the proboscis of hawkmoth pollinators. However, both the average diversity of pollen deposition sites and the average difference of operative length between sphingophilous plant species present in the same community were not significantly different than expected under a null model. When analyzing the results in individual communities, nine communities showed a diversity of pollen deposition sites significantly higher than expected by chance and two communities showed a difference in the operative length greater than expected by chance. These results suggest that other factors such as the degree of generalization in pollination, phenology and / or the use of distinctive floral signals may be avoiding competition for pollinators between coexisting plants species.