Patchiness in the dispersion of nectar resources: Probable causes.

Populations of Delphinium nelsonii have been shown to be patchy with regard to standing crop of nectar available to pollinators (Pleasants and Zimmerman 1979). Plants with relatively large amounts of nectar ("hot plants") are associated with other hot plants while plants with relatively small amounts of nectar ("cold plants") are found near other cold plants. Two possible explantations for this pattern exist: 1. Plants in close proximity to one another may have similar nectar production rates or; 2. The patterns of foraging bumblebees might create the observed nectar distribution pattern. By sampling standing crop of nectar in a D. nelsonii population during periods of both high and low bumblebee abundance evidence was gathered indicating that hot and cold spots are caused by bumblebees.