Submitted to: Annals Of Botany
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/24/2009
Publication Date: 6/1/2009
Citation: Brunet, J. 2009. Pollinators of the Rocky Mountain Columbine: Temporal Variation, Functional Groups and Association with Floral Traits. Annals Of Botany. 103:1567–1578. Interpretive Summary: High pollinator diversity and variation in the composition and abundance of a pollinator fauna over time and space can affect the potential for gene flow for a crop species. Spatial and temporal variation in pollinator composition and abundance can impact the likelihood estimation of the risk assessment process. In this study we examined the temporal and spatial variation in pollinator composition and abundance for the rocky mountain columbine, the plant species we use as a model system to determine the impact of insect pollinators on gene flow or gene escape via pollen. We also examined how the variation in pollinators correlated with different floral traits in the plant species. We detected significant variation in the abundance of the two major pollinators, hawkmoths and bumble bees, over geographical areas and over time in the northwest Colorado region. We found that whiter flowers were associated with the annual presence of hawkmoths and that populations visited by one moth species, Sphinx vashti, had longer spurs than populations visited only by Hyles lineata, the second hawkmoth species that visited A. coerulea flowers. Therefore specific floral traits were associated with specific pollinators. This study stresses that pollinator composition and abundance can vary substantially over the landscape and in time hence that temporal and spatial variation in pollinator composition should be considered in the risk assessment process of insect-pollinated crops. In addition, our results indicate that a potential switch in pollinators for some of our crops may also require a switch in some of the floral features of the cultivated crop in order to maintain high yield.
Technical Abstract: Pollinators together with other biotic and some abiotic factors can select for floral traits. However, variation in pollinator abundance over time and space can weaken such selection. In this study, we examined the variation in pollinator abundance over time and space in populations of the rocky mountain columbine. We also described the variation in three floral traits and examined correlations between pollinator type, functional pollinator groups or altitude and floral traits. Pollinator observations took place in six Aquilegia coerulea populations over one to four years and spur length, flower color and sepal length were measured in 12 populations. Pollinator abundance, measured as visits per flower per hour, was compared among populations and years. Pollinators were grouped into two functional groups: pollen or nectar collectors. We examined the following associations: annual presence of hawkmoths and whiter flowers with longer spurs; the presence of Sphinx vashti and longer spurs; and higher altitudes and whiter flowers. We determined whether an increase in the proportion of hawkmoths in a population was associated with whiter and larger flowers with longer spurs. The abundance of different pollinator groups varied over time and space. Floral traits varied among populations. Higher altitude was correlated with bluer flowers. Whiter flowers were associated with the annual presence of hawkmoths. Populations visited by Sphinx vashti had longer spurs than populations visited only by Hyles lineata. Populations with greater percentage of nectar-collecting pollinators did not have whiter, larger flowers with longer spurs. Despite the large variation in pollinator abundance over time and space, one species of bumble bee or hawkmoth tended to predominate in each population each year. Future studies should examine the specific influences of pollinators and the environment on flower color and of hawkmoth species on spur length, in this plant species.