Biology ETDs

Publication Date

Summer 7-15-2019


Changes in a regional bee assemblage were investigated by repeating a 1970s study from the U.S. Southwest of bees visiting native sunflower (Helianthus annuus). Results showed declines in abundance and species richness of native bees and increases in non-native Apis mellifera. Climate data indicate drought increased over the 40-year period, favoring introduced and generalist species. Experimental placement of A. mellifera in an area of low A. mellifera density in New Mexico reduced native bee visitation, but improved reproduction in H. annuus plants. Meta-analytic models comparing pollination effectiveness in specialist versus generalist, native versus non-native, and native pollinators versus introduced A. mellifera indicated no support for greater specialist effectiveness, but higher effectiveness of native bumble bees (Bombus spp.) compared to non-native pollinators, especially A. mellifera. Changes in pollinator species composition, particularly replacement of native pollinators by introduced A. mellifera, affect plant reproduction and may cascade to changes in plant community composition.




honey bee; pollinator decline; Helianthus annuus; sunflower visitation; dietary specialization; bee conservation; Apis mellifera; introduced species

Document Type


Degree Name


Level of Degree


Department Name

UNM Biology Department

First Committee Member (Chair)

Kenneth Whitney

Second Committee Member

Scott Collins

Third Committee Member

Paula Kleintjes-Neff

Fourth Committee Member

Diane Marshall

Fifth Committee Member

Kelly Miller

Included in

Biology Commons