Forced evolution

Plants shift towards self-pollination as they see disruption in interactions with insects due to changes in climate

- HIMANSHU N

DISRUPTION IN interaction between plants and pollinator species is undoing millions of years of co-evolution. In a December 2023 study published in the journal New Phytologist, scientists from the University of Montpellier, France say field pansy (Viola arvensis) has shown rapid evolution towards “selfing syndrome”, in which the predominantly cross-pollinating plant begins to self-pollinate due to weakened interactions with pollinators. New generations of field pansy flowers were 10 per cent smaller, produced 20 per cent less nectar and were less visited by pollinators compared to their ancestors, say the scientists.

Field pansy is a low-growing plant with pale creamy-yellow flowers. The plant is considered a native of southeastern Europe and western and now grows in temperate zones. The scientists used a “resurrection ecology” approach, in which they grew dormant seeds collected from four populations of field pansy in 1990s-2000s, along with their descendants (collected in 2021). They also noted that pollinators have declined in their study region over the past few years.

The study compared various traits, including production of seeds in the presence and absence of pollinators. They also monitored how bumblebees interacted with the grown field pansy populations. The scientists note that in three of the four populations studied, the descendants showed an average increase of 27 per cent in selfing rate compared to ancestors. The plants also showed a marginal increase in the ability to set seeds over time.

Pierre-Olivier Cheptou, co-author and supervisor of the study, says that field pansy is reducing attractiveness and “giving up” on pollinators.