Overall diversity and presence of bumblebees (Bombus spp.) have been shown to be declining at an alarming rate since the late 1900s. Disappearing habitat due to agricultural and urban development seems to be an important cause of this concerning trend. A surge of public interest has yielded solutions through a combination of agricultural field restoration, allowing fields to fallow, and seeding primarily native wildflower mixes. This has had a definitive positive effect on bumblebee abundance. Insufficient research has been conducted to ascertain which restoration methods, if any, render the greatest advantage to bumblebee populations. This study sought to quantify the protein richness of pollen loads delivered to hives of Bombus impatiens by foragers located in native-dominant warm-season fields and invasive-dominant cool-season fields. We measured the protein content and pollen species profile of pollen loads obtained from wild B. impatiens. The two questions we intended to answer were: 1) Do the species of pollen collected by B. impatiens foragers change with habitat? 2) Does habitat composition affect the nutritional value of pollen loads delivered by B. impatiens foragers? This study offers new information about bumblebee resource flows within the different habitats where they exist.
Results/Conclusions
We observed no significant difference between warm and cool-season fields in pollen frequency among three of the most abundant species groupings. These observations included Solanum carolinense, Trifolium spp., and a combined value of frequently occurring unknown species. The dominant presence of S. carolinense, Trifolium spp., and unknown species suggests that B. impatiens may search for a select number of species for pollen collection. Protein content of pollen loads did not differ significantly between warm- and cool-season fields. The similarity in pollen load species composition from bees foraging in the two field types seems to result in a similar nutritional access in both fields. Though native-dominant warm-season fields may not offer any greater benefits to bumblebees than cool-season fields, they still offer many beneficial ecological services and encourage a greater amount of biodiversity than invasive-dominant cool-season fields which can contribute to an array of food resources for different animal species and opportunities for shelter and nesting less likely to occur in cool-season fields. Following the idea that bumblebees search for preferred pollen species regardless of its abundance within their habitat, future studies have the opportunity to identify the most preferred plant species of bumblebees in order to best inform restoration efforts.