The Bombus lucorum complex – a study across urban and rural habitats

During summer 2018, Trinity College Dublin undergraduate student, Maeve McCann, carried out a research project using molecular methods to identify individual bumble bees belonging to the Bombus lucorum complex. She wrote a blog about her fieldwork back in July, and now she has completed her project. Here’s what she found…

Summary:

Bumble bees are commercially and ecologically important pollinators. They are declining in Ireland due to climate change, land use change and habitat loss. To inform effective conservation it is vital that species distribution and abundance is known. Four of the most common bumble bees in Ireland, belonging to the Bombus lucorum cryptic complex, require molecular identification through PCR/RFLP digest to distinguish individual species, as morphological characteristics are shared in a cryptic manner.

Picture2
Taxonomy of the Bombus sensu stricto subgenus in Ireland. The species highlighted in green are species of bumble bee present in Ireland that are indistinguishable using normal morphological identification methods. Bombus terrestris queens are distinguishable by their buff tail, however workers usually have the colour banding pattern of the lucorum complex, and so are considered part of cryptic complex. Any ambiguous records for these 4 species are referred to Bombus lucorum agg (aggregate).

Our study used molecular techniques to identify bees from the urban and rural settings of Dublin city and County Fermanagh respectively.

Picture3
Dublin city, situated on the eastern seaboard of Ireland, is shaded blue. County Fermanagh, part of Northern Ireland, in the north-west of Ireland is shaded green.

We were able to identify a total of 98 individuals, which revealed a unique species composition in each region. In Dublin, individuals were identified as Bombus cryptarum (4.2%), Bombus lucorum (8.3%) and Bombus terrestris (87.5%); and in Fermanagh, Bombus cryptarum (46%), Bombus lucorum (20%) and Bombus terrestris (34%).

Picture1
A Bombus cryptarum worker caught at Killykeegan Nature Reserve in Co. Fermanagh. Its banding pattern of a yellow band on the thorax and abdomen and a white tail is shared by members of the Bombus sensu stricto subgenus.
Picture6
Species composition by region. The Dublin pie chart corresponds to the following percentages for each species: B. cryptarum (blue) = 4.2%, B. lucorum (orange)= 8.3% and B. terrestris (grey)= 87.5%. The Fermanagh pie chart shows species composition of: B. cryptarum (blue) = 46%, B. lucorum (orange) =20% and B. terrestris (grey) =34%.

No Bombus magnus individuals were found.

Conclusions:

This research project has shown differentiation in the species composition of the B. lucorum complex across a rural and urban setting. The species present varies between each region, but pooled regional data are mostly representative of each site within the region. While the findings show clear regional differences, this difference in species composition could indicate that these species are variable with regard to their preference for a rural or urban environment. However, the extent to which the B. lucorum complex reliably differentiates across all of Ireland can only be assessed by an all-Ireland study controlled for these rural and urban differences. As it stands, B. cryptarum and B. magnus are data deficient, however it could be noted that much of the data on B. lucorum is inconclusive as it too is also deficient on high quality (molecular) identifications.  More investigation is required to understand the ecology of each species uniquely and thus inform conservation strategies.

Download the full report here.

Maeve McCann is an undergraduate Science student at Trinity College Dublin, and her project was supported by the C.B. Dennis British Beekeepers’ Research Trust.

 

 

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