Plant origin and other attributes impact bee forage patterns in a common garden study in Maine, United States; part II.
In a common garden study in Maine from 2012 to 2015, we used two bee species (Apis mellifera L. and Bombus ternarius Say (1837)) and three field-recognizable bee categories ('Most Bombus', 'Halictidae', and 'Other Bees') plus an 'All Bees' data aggregation to compare 17 native and 68 introduced plant taxa. Data were from three 1-min timed periods per flowering plant taxon on a given day at a site. We observed 17,792 bees and found that their response varied by bee species or group. Using mixed models to analyze our data, we found that native bees had higher visitation rates on native plants, while A. mellifera visited both native and introduced plants. Most groups visited native late-flowering and native mid-late-flowering plants at higher rates. 'All Bees' were attracted to native perennials (vs annuals and shrubs) and to tall plants, both native and introduced; A. mellifera was attracted to introduced perennials, to introduced tall plants, and to lower-growing native plants. Asclepias tuberosa L. elicited a strong response from B. ternarius. In only two of six pairs of wild types and cultivars, bees visited wild types more. Plants with long bloom periods and with small, densely arranged white flowers attracted higher bee visitation than did other configurations (e.g., Origanum vulgare L., one of our most attractive taxa). A general linear model showed that linear combinations of flower density, floral resource height, flower corolla depth, and flowering duration explained significant variation in visitation rates for each of the different bee taxa groups.