Does city life make bumblebees larger?

Date:
August 17, 2020
Source:
Martin-Luther-Universita"t Halle-Wittenberg
Summary:
Does urbanization drive bumblebee evolution? A new study provides
an initial indication of this. According to the study, bumblebees
are larger in cities and, therefore, more productive than their
rural counterparts.

The research team reports that differences in body size maybe
caused by the increasingly fragmented habitats in cities.



FULL STORY ==========================================================================
Does urbanisation drive bumblebee evolution? A new study by Martin Luther University Halle-Wittenberg (MLU) and the German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig provides an initial
indication of this. According to the study, bumblebees are larger in
cities and, therefore, more productive than their rural counterparts. In Evolutionary Applications, the research team reports that differences in
body size maybe caused by the increasingly fragmented habitats in cities.


==========================================================================
Over the last 200 years, the habitat of bumblebees and other insects has changed dramatically. Now they are less likely to live in rural areas
but more likely to be surrounded by roads and concrete walls. "Living
in a city can have both benefits and disadvantages for bumblebees. One
the one hand, residential gardens and balconies, allotment gardens,
botanical gardens and city parks provide rich food sources for
bumblebees. On the other hand, cities are significantly warmer than their surrounding rural areas. In addition, impervious surfaces, streets and
large buildings create considerably smaller habitats that are isolated
from one another. These might pose a challenge to bumblebees," says Dr Panagiotis Theodorou from the Institute of Biology at MLU, who led the
research at MLU and iDiv.

The team of biologists at MLU wanted to find out whether urbanisation is associated with shifts in bumblebee body size with consequences on the ecosystem service of pollination they provide. The scientists collected
more than 1,800 bumblebees in nine German metropolitan areas and their
rural surroundings and used potted red clover plants as reference for pollination in all locations. Their work concentrated on three locally
common bumblebee species: the red-tailed bumblebee (Bombus lapidarius),
the common carder bee (Bombus pascuorum) and the buff-tailed bumblebee
(Bombus terrestris). The researchers measured the body size of every
bumblebee they caught and counted the number of seeds produced per red
clover plant. "Our results show that bumblebees from more fragmented
urban areas were larger compared to their rural counterparts, by around
four percent," says biologist Dr Antonella Soro from MLU. The results
were similar for all three bumblebee species.

Body size is linked to an organism's metabolism, life history, space use
and dispersal as well as a major determinant of species interactions,
including pollination. "Larger bumblebees can see better, they have
larger brains and they are better in learning and memory. They are also
less likely to be attacked by predators and can travel greater distances,
which is an advantage in a fragmented landscape such as the urban one. In addition, large bumblebees visit more flowers per flight and are capable
of depositing a higher number of pollen grains on stigmas, which makes
them better pollinators," says Soro. This might be the explanation of
the positive relationship between body size and pollination documented
by the researchers. The study gives an indication that the severity
of habitat fragmentation could impact a bumblebee's body size and thus
also indirectly influence pollination. According to Theodorou, there are
still a lot of open questions regarding the effects of urban-related environmental changes on bees and pollination. Therefore, the team
points to the importance of further studies to better understand the evolutionary responses of bees to urbanisation, information that can
help improve urban planning.


========================================================================== Story Source: Materials provided by Martin-Luther-Universita"t_Halle-Wittenberg. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. Panagiotis Theodorou, Lucie M. Baltz, Robert J. Paxton, Antonella
Soro.

Urbanisation is associated with shifts in bumblebee body size,
with cascading effects on pollination. Evolutionary Applications,
2020; DOI: 10.1111/eva.13087 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200817104339.htm

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