Bachelor Thesis

Plant flower trait variation along an altitudinal gradient on La Palma

Sophie Reinermann (07/2014-09/2014)

Support: Manuel Steinbauer, Carl Beierkuhnlein

Floral traits strongly affect a plant’s pollination success and are suspected to change in relation to the pollinator community as well as differing environmental conditions.  In this study shifts in the flower color and mean flower size along an elevational gradient are investigated. Elevational changes of abiotic and biotic factors, as increased UV radiance, harsher wind conditions and a general apparent shift in the pollination community from bee-dominated to fly-dominated influence floral traits. Thus, it is assumed that flower colors change from mainly blue and dark to yellow, white and bright. In addition, mean flower sizes are suspected to decrease along an altitudinal gradient. La Palma, which is the most northwestern island of the Canary Island Archipelago, has strong environmental gradients and therefore exhibits optimal conditions for investigations of variations in floral traits. The altitudinal ranges of every plant species were derived from occurrence information with a resolution of 500x500 m². By using literature and internet sources the flower colors and flower sizes were determined and colors were assigned Munsell color notations using the Munsell color book. To reveal relations between floral traits, color and size, and elevation, regression analyses were carried out. The resulting patterns were all contrary to previous expectations. The flower colors were relatively homogeneously distributed in all elevations. The percentage of white flowers did not increase and the mean flower size showed a peak at mid-elevations. Based on these findings I suggest the following conclusions. The pollination community do either not shift or has not as much influence as expected. Abiotic conditions could play a major role with diverse impacts on color and size. Further investigations are needed to better understand the dependencies between all components.