Date of Award

8-1-1984

Document Type

Thesis

Degree Name

Master of Arts (MA)

Department

Biology

First Advisor

Dr. David Sutherland

Abstract

The pollination ecology of Asclepias incarnata L. subsp. incarnata was studied at three sites in eastern Nebraska and one in western Iowa. A. incarnata was shown to be visited by many species of insects. A few Hymenoptera and Lepidoptera served as efficient pollinators, while the other visitors were primarily nectar thieves. On disturbed sites, Megabombus pennsylvanicus (DeGeer) was the prevalent pollinator, along with Apis mellifera L., Pyrobombus griseocollis (DeGeer), and two species of Sphecinae. On undisturbed sites, A. incarnata was found in much smaller populations and was pollinated by Papilio glaucus L., Danaus plexippus (L.), Epargyreus clarus (Cramer) and other Papilio species. Several Hemipterans, Coleopterans and Homopterans were common herbivores on this plant. Nectar production appeared to peak in the morning hours and decline through the afternoon and evening, with a similar pattern of pollinator occurrence. Although primarily insect pollinated, the plant apparently is capable of self-fertilization to some extent and may occasionally be apomictic or autogamous. Fruit production was affected by numerous factors, including insect predation on pollinators, insect damage to plant and immature fruit, and climatic factors.

Comments

A Thesis Presented to the Department of Biology and the Faculty of the Graduate College University of Nebraska In Partial Fulfillment of the Requirements for the Degree Master of Arts University of Nebraska at Omaha. Copyright 1984 Thomas S. Brotherton.

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