Schematic diagram representing the proportion of <i>Apis mellifera Pgi</i> mRNA covered by <i>Bombus Pgi</i> coding region sequenced in this study (above) and proportion of predicted <i>A. mellifera</i> and <i>B. terrestris</i> phosphoglycerate mutase covered by <i>Bombus Pgm</i> coding regions sequenced in this study (below).

<p>Figures indicate the base positions in the <i>Apis</i> mRNA sequence where the <i>Bombus</i> sequence begins and ends.</p

Network showing the relation between phosphoglucose isomerase haplotypes for all regions (coding and non-coding).

<p>PC = <i>B. pascuorum</i>, HU = <i>B. humilis</i>, PT = <i>B. pratorum</i>, M = <i>B. monticola</i>, L = <i>B. lapidarius.</i> Numbers along the connecting lines indicate the number of mutated positions between haplotypes. Nodes are not proportional to haplotype frequencies.</p

Ecological Variation in Response to Mass-Flowering Oilseed Rape and Surrounding Landscape Composition by Members of a Cryptic Bumblebee Complex

<div><p>The <i>Bombus sensu stricto</i> species complex is a widespread group of cryptic bumblebee species which are important pollinators of many crops and wild plants. These cryptic species have, until now, largely been grouped together in ecological studies, and so little is known about their individual colony densities, foraging ranges or habitat requirements, which can be influenced by land use at a landscape scale. We used mass-flowering oilseed rape fields as locations to sample bees of this complex, as well as the second most common visitor to oilseed rape <i>B. lapidarius</i>, and molecular RFLP methods to distinguish between the cryptic species. We then used microsatellite genotyping to identify sisters and estimate colony densities, and related both proportions of cryptic species and their colony densities to the composition of the landscape surrounding the fields. We found <i>B. lucorum</i> was the most common member of the complex present in oilseed rape followed by <i>B. terrestris</i>. <i>B. cryptarum</i> was also present in all but one site, with higher proportions found in the east of the study area. High numbers of bumblebee colonies were estimated to be using oilseed rape fields as a forage resource, with <i>B. terrestris</i> colony numbers higher than previous estimates from non-mass-flowering fields. We also found that the cryptic species responded differently to surrounding landscape composition: both relative proportions of <i>B. cryptarum</i> in samples and colony densities of <i>B. lucorum</i> were negatively associated with the amount of arable land in the landscape, while proportions and colony densities of other species did not respond to landscape variables at the scale measured. This suggests that the cryptic species have different ecological requirements (which may be scale-dependent) and that oilseed rape can be an important forage resource for many colonies of bumblebees. Given this, we recommend sustainable management of this crop to benefit bumblebees.</p></div

Location of the 14 spring oilseed rape fields in South East Ireland, and proportions of each of the cryptic species identified in each site.

<p>An example of the landscape mapped at a 700 m radius around each field is given, with the focal oilseed rape field highlighted with a dotted line.</p

Sample sizes (A) and Capwire point estimates of number of colonies (B) of the different bee species in the different sites.

*<p>mean of sites with species present only.</p><p>(Site names in bold are those with a total of Oilseed rape and adjacent field together). S = area of focal oilseed rape field, P = % arable land in surrounding landscape, and D = distance to nearest sampled oilseed rape field, measured from the centroid of the oilseed rape field.</p

Results of multiple comparisons of variables from generalized linear models investigating the effects of landscape composition measured within a 700 m radius on proportions and colony densities of each species.

<p>Only models with significant components (marked with a *) are displayed. Proportion estimates are on the logit scale, and colony estimates on log scale. Model fit is calculated as follows: ((null deviance – residual deviance)/null deviance) <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0065516#pone.0065516-Zuur1" target="_blank">[49]</a>.</p

Locations of individuals sampled, by species.

<p>Grid reference is the Ordnance survey in 4-figure format (note that for localities with the same grid reference this refers to a specific 1 km square, not a single point). Dates are in standard UK format (day/month/year). See note in the text regarding likely sampling of individuals from the same nest. An asterisk in the columns headed <i>Pgi</i> and <i>Pgm</i> indicates which samples were sequenced. ^(a) Exact sample locations for each individual were not recorded. However, individuals were sampled at multiple sites between the two locations indicated (all separated by >200 m) and not more than a few individuals were collected from a single locality.</p

Location of amino acid replacements (relative to amino acid sequence alignment position – note <i>Pgi</i> sequence is partial) across species for phosphoglucose isomerase (amino acid sequence based on inferred coding regions, hence putative replacement).

<p>Unless otherwise stated, replacements were observed for all samples within each species named.</p

Negative relationships between amount of arable land in a 700 m radius and a) proportions of <i>B. cryptarum</i> and b) colony densities of <i>B. lucorum</i>.

<p>Points show normalised measured values, and lines show model predictions.</p

Network showing the relation between phosphoglycerate mutase haplotypes for coding regions only.

<p>HR = <i>B. hortorum</i>, PC = <i>B. pascuorum</i>, HU = <i>B. humilis</i>, PT = <i>B. pratorum</i>, M = <i>B. monticola</i>, L = <i>B. lapidarius.</i> Numbers along the connecting lines indicate the number of mutated positions between haplotypes. Nodes are not proportional to haplotype frequencies.</p