Thread by @jaworskicoline

Heatwaves, droughts... We can't ignore climate change ! Does climate change affect plants, pollinators? Does drought affect pollination, the cornerstone of the functioning of terrestrial ecosystems?
>>> Check out our new paper in @JEcology and please retweet !!!!!
a thread 1/17

2/17 Manuscript accepted in @JEcology: Long‐term experimental drought alters floral scent and pollinator visits in a Mediterranean plant community despite overall limited impacts on plant phenotype and reproduction besjournals.onlinelibrary.wiley.com/doi/10.1111/13…

3/17 We measured floral traits in a natural Mediterranean community under drought: floral scent, flower number, colour, size, nectar production. We also measured pollinator visits, species richness and composition, and plant reproduction.

4/17 We used the CLIMED long-term drought exclusion experiment near Marseille.
Rainfall exclusion plots (left); control plots (right, gutters upside down). Typical Mediterranean shrubland: (kermes oak wind-pollinated), rosemary, cistus and thyme (great food resources for bees !).

5/17
Measuring how drought affects floral scent: do you remember that smell when mowing the lawn?

6/17 This is 3Z-hexenol, a typical green-leaf stress marker, and we found it at high concentrations in all drought-stressed plants !

7/17 Does drought also affects the production of floral resources for pollinators?
Only thyme had a reduced production, by almost 4x !!
Nectar production sustained under drought in rosemary and cistus.

8/17 but how about the number of flowers, the colour of flowers, the size of flowers? (all traits are used by pollinators to locate flowers, number and size of flowers correlate with the total quantity of nectar produced).
>>> No effect of drought

9/17 OK but did floral scent alteration affect pollinator visits ?
>>> YES Likely !!! Social bees honeybees and bumblebees preferred non-stressed plants, but small wild bees visited more drought-stressed plants. But no change in species richness.

10/17 Oh, and did that change plant reproduction ?
NO (almost): no effect on number of fruits and seeds nor seed mass. We even measured seed germination:
>>> Germination was slightly lower in cistus, slightly slower in rosemary.

11/17 SO WHY DOES IT MATTER? Why did bees switch resources? Why was floral scent the only trait affected?

12/17 First, this was Spring 2018 data, the wettest of the 10 past years (not quite ideal conditions nor 2022 conditions, but, hay this is research). This means that even under such 2018-moderate drought, we saw major changes ! Imagine what’s happening right now !!

13/17 Second, floral scent is extremely sensitive to environmental conditions. It is composed of dozens of different molecules, some of which byproducts of defensive plant responses, even to moderate stress. This molecules will be detected in floral scent blends by pollinators.

14/17 Third, bees learn fast how to choose the best resources. They must have made a choice for a reason. OK, nectar production did not seem to vary in rosemary or thyme, but how about nectar quality (the fine balance in the ratio of different sugars)? How about pollen quality?

15/17 Oh and why did honeybees and small wild bees made opposite choices? There was a LOT of honeybees there. They are very good at tracking the best resources. Would climate change exacerbate the competition for resources from honeybees over wild bees ? This needs more research!

16/17 Also nectar production in thyme was reduced by 4!! Thyme is a really important species for pollinators in the Mediterranean Basin (doi.org/10.1093/ee/nva…). Hoverflies and wild bees that heavily rely on this resource may suffer more (lack food) under climate change.

17/17 Conclusion: even moderate drought causes major changes in floral scent and pollinator choices. Consequences of climate change are much worse, extended and complex than tested here. Climate change matters to all living things!

This research was made possible by @AXAResearchFund , @imbe_marseille, @OxfordBiology  @CamZoology. It took us 5 years and involved many collaborators, including @BenGeslin, @MarieZakardjian, @OwenTLewis and @CEROxford, @LynnDicks and many more !

Thanks to the GDR MediatEC, Diane Campbell, Rob Raguso, @rr_junker, @LiseRops, Mathieu Santonja, @CamiloZalamea Nicolas Barthes, Maxime Hervé, Eric Meineri, Julien Renoult, David Genoud, Matthieu Aubert, Eric Dufrêne, Christophe Lauriaut, Jean-Pierre Hébrard, @julien_ruffault

#pollinators #ClimateCrisis #biodiversity #bees @cmhmaliani @LucaCarisio @lucie_schurr @BenoitPujol @jakecologist @a_kantsa @FeitBen @MathildeBaude @sarahkrichman @sara_lil_plants @LChittka @JeffOllerton @JaneCStout @ElliLeadbeater1

@elizalicollin