Date of Award

2025

Degree Name

Biological Sciences

College

College of Science

Type of Degree

M.S.

Document Type

Thesis

First Advisor

Dr. Pamela Puppo

Second Advisor

Dr. Kyle Palmquist

Third Advisor

Dr. Jarrad Prasifka

Abstract

Sunflowers (Helianthus, Asteraceae) are an important crop used for oil, dye, fodder, and edible seeds. Long-horned bees (Melissodes, Apidae) are solitary species native to the Americas that specialize in sunflower pollination; they are among the most frequent visitors to sunflowers, and have been shown to enhance yield, offering considerable economic benefits to sunflower production. This study used metabarcoding to investigate the foraging habits of two understudied Melissodes species, M. trinodis and M. agilis. Using the ITS2 and trnL barcodes, our study aimed to (1) investigate the plants visited by M. agilis and M. trinodis and (2) assess the distances Melissodes fly to collect pollen by comparing the composition of pollen on bees collected from sunflower field centers vs. edges. For this, we collected a total of 138 female bees in 2022 from three sunflower fields in Minnesota and North Dakota, two with some pesticide use, and one organic farm with no pesticide use. Our results corroborate the specialized nature of Melissodes and their strong preference for sunflowers despite other available resources, as 99% of the reads recovered from the pollen were from Helianthus. Due to the abundance of Helianthus pollen, no significant difference was found in the pollen collected by M. agilis or M. trinodis, and no difference was found between the pollen collected at field centers or field edges. We found small amounts of pollen from other Asteraceae genera, and pollen from the legume family, Fabaceae, mainly alfalfa (Medicago sativa), yellow sweet clover (Melilotus officinalis), and white sweet clover (Melilotus albus). We provide the first record of Melissodes spp. visiting peppers (Capsicum, Solanaceae), and hazel (Corylus, Betulaceae). We estimated that one M. agilis specimen traveled 16 m, supporting hypotheses that Melissodes have small foraging ranges. Bees collected pollen from vascular plants only on the two conventional farms (with pesticide use), but at the organic farm, we identified an additional eight genera of algae and a bryophyte (Marchantia polymorpha subsp. ruderalis). Overall, our results contribute vital information on the foraging preferences of an important solitary bee and confirm they are sunflower specialists, while also identifying other crop species that may benefit from Melissodes pollination and could be planted near sunflower fields to supplement their diet before or after sunflower bloom.

Subject(s)

Entomology.

Ecology.

Apidae.

Compositae.

Pollinators.

Sunflowers.

Bees.

Pollination.

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