Bee flight suffers under temperature extremes

Date:
August 18, 2021
Source:
Imperial College London
Summary:
Rising temperatures could help some northern-latitude bees fly
better, but more frequent extreme weather events could push them
past their limits.



FULL STORY ========================================================================== Rising temperatures could help some northern-latitude bees fly better, but
more frequent extreme weather events could push them past their limits.


========================================================================== Bees' flight performance affects their ability to pollinate plants --
a crucial service for many of our crops. Now, researchers from Imperial
College London have measured the relationship between bumblebee flight performance and surrounding temperature.

Measuring the motivation of bumblebees to fly and their flight endurance,
the team found performance rose rapidly from the lower tested limit
of 12oC and peaked between 25-27DEGC. Beyond this, however, they found performance started to decline.

Their results indicate that whilst bumblebees found in more northern
latitudes may see benefits to flight performance under future climate
warming, populations in southern latitudes, where temperatures above
27oC are more readily exceeded, may be adversely affected. The results
are published today in Functional Ecology.

First author Daniel Kenna, from the Department of Life Sciences (Silwood
Park) at Imperial, said: "Climate change is often thought of as being
negative for bumblebee species, but depending on where in the world they
are, our work suggests it is possible bumblebees will see benefits to
aspects of an important behaviour.

"However, more extreme weather events, such as cold snaps and the
unprecedented heatwaves experienced in recent years, could consistently
push temperatures beyond the comfortable flight range for certain species
of bumblebees.



========================================================================== "These risks are particularly pertinent for 'fixed colony' pollinators
like bumblebees, which cannot shift their position within a season
if conditions become unfavourable, and potentially provide a further explanation as to why losses have been observed at species' southern range limits." Like most flying insects, air temperature influences bees' body temperature, and body temperature influences flight activity. Too cold
and their flight muscles can't function fast enough to support flight;
too warm and they could overheat.

To measure how flight is determined by air temperature, the team
temporarily attached bumblebees to 'flight mills', which allowed them
to fly in circles like a carousel, capturing the distance and speed
of flight. They tested bees ranging in body size at temperatures from
12-30DEGC and used their results to construct a thermal performance curve (TPC).

This TPC predicts that whilst bumblebees can fly around 3km at their
thermal optimum, this average flight distance could be reduced to under
1km when temperatures rise to 35DEGC, and could plummet to just a few
hundred metres at a chilly 10DEGC.

At temperatures of 15DEGC and below, the team observed that bees were demotivated to fly and frequently would not fly past 100m. Moreover,
it was only the bigger sized bees that successfully flew at these low temperatures, suggesting smaller individuals dislike cold days but may
benefit more from climate warming.

Lead researcher Dr Richard Gill, from the Department of Life Sciences
(Silwood Park) at Imperial, said: "While we still need to understand
how these findings translate to factors like foraging return to colonies
and pollination provision, as well as applicability to other bumblebee
species, the results can help us understand how smaller versus larger
flying insects will respond to future climate change.

"It's not just pollination: how different flying insects respond to
warming temperatures could also affect the spread of insect-borne diseases
and agricultural pest outbreaks that threaten food systems. Applying
our experimental setup and findings to other species can help us to
understand future insect trends important for managing service delivery
or pest control methods." The team are looking to expand this research
to understand how climate warming and extreme weather events can influence
the impacts of other stressors, such as pesticide exposure. They are also looking at how the impacts of warming can affect pollination delivery
across different types of landscapes.

========================================================================== Story Source: Materials provided by Imperial_College_London. Original
written by Hayley Dunning. Note: Content may be edited for style and
length.


========================================================================== Journal Reference:
1. Daniel Kenna, Samraat Pawar, Richard J. Gill. Thermal flight
performance
reveals impact of warming on bumblebee foraging
potential. Functional Ecology, 2021; DOI: 10.1111/1365-2435.13887 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/08/210818083941.htm

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