Pollen load composition and size in the leafcutting bee Megachile rotundata (Hymenoptera: Megachilidae)

Abstract

We examined how the species composition and volumes of pollen loads of Megachile rotundata varied seasonally and among females of different body sizes. Alfalfa and mustards (Brassicaceae) made up, on average, 88-95% of the pollen load volumes in each of three seasonal samples; in total, the 300 females sampled carried ten different pollen types. Because of variation in pollen grain size among plant species, estimates of the contribution of different species to pollen loads, based on pollen counts only, differed from those adjusted for pollen grain size. The overall size of pollen loads, as well as the contribution of alfalfa declined seasonally, while that for mustards (with smaller individual grain sizes) increased. The type of pollen carried by females did not vary with body size, but we found a significant relationship between female size and the size of the largest loads. Surprisingly, females of intermediate size carried the largest pollen loads, whether measured by counts or volume.Megachile rotundata / alfalfa / pollen load composition / seasonal variation / body size

The effects of time, temperature and plant variety on pollen viability and its implications for gene flow risk

“…While we expect low pollen viability to limit gene flow potential, one might argue that bees carry thousands of pollen grains, for example leafcutting bees can carry 100,000 pollen grains (O'Neill & O'Neill ), and therefore plenty of viable pollen grains are available to fertilise the ovules. Under such circumstances, pollen viability would not be expected to have much impact on seed set or on gene flow potential.…”

Fragmentation of nest and foraging habitat affects time budgets of solitary bees, their fitness and pollination services, depending on traits: Results from an individual-based model

“…We assumed a short time at the nest after each trip and we neglected time needed for egg laying, cell closure and other activities (due to data deficiency and unnecessary complexity, see also [37] for a discussion). We further assumed that all pollen collected at the flowers reach the nest, while in reality pollen gets lost on the way [76] and solitary bees of the same species return to the nest with a high variability of pollen loads [77]. Also, in favourable landscapes bees may be egg-limited rather than pollen limited [38].…”

Nesting biology ofMegachile(Chrysosarus)guaraniticaand high mortality caused by its cleptoparasiteCoelioxys bertonii(Hymenoptera: Megachilidae) in Brazil

“…A low diversity of pollen types from brood cell contents or from female bodies was also documented for other studies with Megachile species (Müller & Bansac ; Buschini et al . ; O'Neill & O'Neill ; Torretta et al . ; Landry et al .…”

“…samples (Buschini et al . ); pollen grains of alfalfa, Medicago sativa L. (Fabaceae) (52%), and mustard (Brassicaceae) (42%) were found on bodies of 300 females of Megachile ( Eutricharaea ) rotundata (Fabricius) (O'Neill & O'Neill ), and two types of Asteraceae pollen reached more than 80% of the total amount found in brood cell samples of M . ( Pseudocentron ) gomphrenoides Vachal (Torretta et al .…”