'Manipulation of soil mycorrhizal fungi influences floral traits'

Hi Folks!

As many of you in the northern hemisphere are likely doing, I've been contemplating the awakening of roots, soils, fungi, and all that are below the soil, ice, and frost.

If you're into the science, and research happening right now on mycorrhizal fungi, do take a look at this recently published study, having to do specifically with floral traits responses to AMF.

When you're out there this Springtime watching the pollinators drift from bloom to bloom, you may think back to that soil and those fungi being a part of the little big picture.

https://nph.onlinelibrary.wiley.com/doi/10.1111/nph.19625?fbclid=IwAR0oazPZyZaihaOTAEd5x7FXkHgvDe1V3ehEcT55FFVpb3WZ0Hsl6_qgyhA

Excerpt 1

Most plants form root hyphal relationships with mycorrhizal fungi, especially arbuscular mycorrhizal fungi (AMF). These associations are known to positively impact plant biomass and competitive ability. However, less is known about how mycorrhizas impact other ecological interactions, such as those mediated by pollinators.
We performed a meta-regression of studies that manipulated AMF and measured traits related to pollination, including floral display size, rewards, visitation, and reproduction, extracting 63 studies with 423 effects.
On average, the presence of mycorrhizas was associated with positive effects on floral traits. Specifically, we found impacts of AMF on floral display size, pollinator visitation and reproduction, and a positive but nonsignificant impact on rewards. Studies manipulating mycorrhizas with fungicide tended to report contrasting results, possibly because fungicide destroys both beneficial and pathogenic microbes.
Our study highlights the potential for relationships with mycorrhizal fungi to play an important, yet underrecognized role in plant–pollinator interactions.

Excerpt 2

Overall, we found strong support for the hypothesis that the presence of AMF can positively impact floral display size. We also found support for effects of AMF on pollinator visitation and yield. The studies we extracted from our search cover a broad range of study objectives, methods (especially treatments), and plant/AMF taxonomic groups. This breadth of systems and approaches likely explains the high among-study heterogeneity we encountered.

Several key questions about the effects of AMF on pollinator-mediated interactions remain unanswered: (1) How widespread are they? (2) To what degree does the effect of AMF depend on the specific plant and AMF species involved? (3) How important are environmental drivers such as soil fertility and drought? And, more broadly, (4) what role do interactions with AMF play in plant demography and community assembly? To address the first and second questions, more studies examining the effects of AMF on floral traits across a variety of species, systems, and settings are needed. For example, a large number of the studies we extracted applied AMF from the family Glomeraceae (common in commercially available products). This concentration of studies examining the effects of species from a single order limits our ability to estimate whether, for example, other taxonomic groups of AMF are more or less potent drivers of floral traits. Conversely, the combination of AMF and plant species may be very important to the outcome (Stahlhut et al., 2023). Thus, studies that apply a commercial AMF product could be a poor approximation for outcomes in natural systems. For point (3), more studies that specifically examine the impacts of AMF on floral traits under different environmental conditions are needed. Finally, for (4), while some evidence exists to suggest that interactions with AMF can be potent drivers of pollinator-mediated community dynamics (e.g. Cahill et al., 2008), there is not currently sufficient information available to determine whether these effects are widespread. All of these questions require more study to adequately address them.

Our meta-analysis adds to a growing body of work connecting above- and belowground ecological interactions. While the effects of AMF on plant biomass are well-recognized, our results imply that a plant's interactions with its soil microbiome extend well beyond typical growth and biomass metrics and involve a broader set of critical aboveground interactions. The implications are potentially far-reaching – for example, if pollinator preference for floral traits such as specific floral pigments, VOCs, and/or floral display size are mediated by the plant's relationship(s) with mycorrhizal fungi, this suggests links between floral traits, pollinator-mediated fitness and the plant-AMF symbiosis. At the same time, we lack studies that connect AMF-associated changes in floral display size to changes in pollinator-mediated fitness across a variety of systems, approaches, and settings.

Cool!