Global warming impairs the chemical attractiveness to pollinators

Abstract

Global warming is expected to impact the chemical communication between flowering plants and their pollinators. Here, we aimed to test by chemical analytical, electrophysiological, and behavioral approaches whether temperature-induced shifts in floral scent of strawberry (Fragaria x ananassa) affect chemical communication with its main bee pollinators (Apis mellifera, Bombus terrestris, Osmia bicornis). While strawberry flowers in the optimum scenario released 10.4 ng/flower/hour, mainly p-anisaldehyde (81%) and seven other scent compounds, in the warmer scenario, the flowers did not emit any detectable scent. In the behavioral experiments, the pollinators were attracted by the scents of the optimum scenario. We predict that the absence of detectable scent emissions from strawberry plants grown under heat stress will drastically reduce the attractiveness of the flowers to the pollinators. Our study raises important ecological and agricultural questions, as decreased attractiveness of flowers to pollinators might result in insufficient pollination with negative consequences for ecosystem functioning and crop yields.

Floral Scents in Bee-Pollinated Buckwheat and Oilseed Rape under a Global Warming Scenario

“…Thus, bees have the capability to detect compounds that disappear at increased temperatures or are affected in their (relative) amounts. Some of the EAD-active compounds were already identified as being electrophysiologically active in both A. mellifera and B. terrestris (e.g., linalool, ( E )- β -ocimene, p -anisaldehyde [ 24 , 30 , 56 , 57 , 58 , 59 ]). The main compounds 2- and 3-methylbutanoic acid were demonstrated here for the first time as eliciting antennal responses in bees.…”

“…Some studies have recorded decreased emissions and changes in the composition of floral scents under heat stress [ 26 ] ( Lilium auratum Lindl. ), [ 27 ] ( Globularia alypum (L.), Quercus ilex L., Dorycnium pentaphyllum Scop., Spartium junceum L.) and [ 29 ] ( Jasminum auriculatum Vahl), with one study even documenting that a plant species (strawberry, Fragaria x ananassa Duch) no longer produced detectable flower scents when exposed to heat stress [ 30 ], whereas other studies did not detect an effect of heat stress on floral scent emissions, [ 25 ] ( Trifolium repens L.) and [ 70 ] ( Petunia axillaris Lam.). Thus, some plants are more heat tolerant and resilient than others when it comes to signaling by floral scents.…”

“…So far, there is a large gap in our understanding of how floral scents of crop plants are affected by climate warming. Studies of non-crop species, however, have shown that qualitative and quantitative floral scent properties are affected by increased temperatures [ 25 , 26 , 27 , 28 , 29 ], and a very recent study on strawberry even demonstrated that flowers stop producing detectable amounts of scent when grown at temperatures 5 °C higher than optimal temperatures ([ 30 ]). These changes in floral scent may cause inefficient pollinator attraction [ 31 , 32 , 33 , 34 ] in the future, considering that global mean surface temperatures are increasing [ 35 ].…”