Wildflowers are self-fertilizing to deal with a lack of pollinators

A new study from CNRS and the University of Montpellier provides yet another example of how human activities are impacting the natural world. 

The experts have discovered that flowering plants in farmlands are increasingly adapting to self-fertilization due to the widespread decline of insect pollinators.

Challenging conditions 

This adaptation is a direct response to the challenging conditions faced by plants as reproduction becomes more difficult for them in an environment depleted of pollinating insects.

“Plant-pollinator interactions evolved early in the angiosperm radiation. Ongoing environmental changes are however leading to pollinator declines that may cause pollen limitation to plants and change the evolutionary pressures shaping plant mating systems,” wrote the study authors.

Focus of the study

The research team conducted a comparative study involving field pansies, analyzing both current specimens and those grown from seeds collected between 1992 and 2001. 

“We used resurrection ecology methodology to contrast ancestors and contemporary descendants in four natural populations of the field pansy (Viola arvensis) in the Paris region (France), a depauperate pollinator environment,” wrote the researchers.

“We combine population genetics analysis, phenotypic measurements and behavioral tests on a common garden experiment.”

Alarming findings

The researchers found that today’s flowers are approximately 10% smaller, produce 20% less nectar, and attract fewer pollinators than their predecessors.

According to the experts, their analysis revealed a 27% increase in realized selfing rates in the field during the study period. 

“We documented trait evolution towards smaller and less conspicuous corollas, reduced nectar production and reduced attractiveness to bumblebees, with these trait shifts convergent across the four studied populations.”

Rapid evolutionary response 

This change in the plants’ traits is thought to be a rapid evolutionary response to the decline in pollinator populations across Europe. 

Alarmingly, a separate study in Germany highlighted this issue, noting a 75% reduction in the biomass of flying insects in protected areas over the past thirty years.

Vicious cycle 

The CRNS study reveals a concerning feedback loop: the decline in pollinators leads to reduced nectar production, which could further exacerbate the decline of these essential insects. 

This vicious cycle poses a significant threat to the longstanding symbiotic relationship between plants and pollinators, a relationship that has existed for millions of years.

Study implications 

“In summary, our study highlights the potential of natural populations to respond quickly to environmental changes. However, such evolutionary responses may have impacts on ecological interactions, here plant–pollinator interactions, and potentially cascading trophic consequences in ecosystems,” wrote the study authors. 

“There is thus an urgent need to investigate whether these results are symptomatic of a broader pattern among angiosperms and their pollinators, and if so understanding whether there is a possibility to reverse this process and break this eco-evolutionary-positive feedback loop.”

The study is published in the journal New Phytologist. 

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