GIS and path analysis: examining associations between the birds, the bees, and plant sex in Echinocereus coccineus (Cactaceae)

Abstract

We tested hypotheses of how pollinators and water resource gradients influence the evolution of dioecy using Echinocereus coccineus, a cactus with both hermaphroditic and dioecious populations growing over wide climatic and biotic gradients in the Madrean Archipelago. A GIS database was compiled from herbarium specimens, rainfall data, and hummingbird abundance records. We used structural equation modeling to assess the relative direct and indirect influence of hummingbird abundance and mean annual rainfall on the presence of dioecy. The best fit models contained a direct influence of hummingbird abundance on dioecy; any direct effect of rainfall was negligible. These results support pollinator selection as the major influence on evolution of gender in Echinocereus coccineus.

Parent Publication

• Connecting mountain islands and desert seas: Biodiversity and management of the Madrean Archipelago II

Citation

Scobell, Summer; Schultz, Stewart. 2005. GIS and path analysis: examining associations between the birds, the bees, and plant sex in Echinocereus coccineus (Cactaceae). In: Gottfried, Gerald J.; Gebow, Brooke S.; Eskew, Lane G.; Edminster, Carleton B., comps. Connecting mountain islands and desert seas: biodiversity and management of the Madrean Archipelago II. Proc. RMRS-P-36. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station: 438-443