Bengaluru: If you were a hoverfly, part of a species that is among the most important pollinators in the world, flowers in Sikkim may perhaps be more attractive than even the ones found in Sweden or Bengaluru.
The simplest of the scientific questions, “How does one of most important pollination species in the world select its flowers?” has lead not only to greater understanding of the pin-head-sized brains of hoverflies, but could also hold key answers for the protection of wild pollinators.
The global collaboration involved researchers from Uppsala University in Sweden, Flinders University in Australia and National Centre for Biological Sciences (NCBS) in Bengaluru.
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Through patient observations where teams lead by Shannon Olsson (NCBS) and Karin Nordström (Uppsala University) followed flies for months, scientists tabulated the behaviour of hoverflies in tropical climes of outskirts of Bengaluru, mountainous northern Sikkim and hemiboreal (landscapes close to the sub-artic regions) of Uppsala Sweden.
The observations — published recently in the journal PNAS , or Proceedings of the National Academy of Sciences of the United States of America — showed that the tiny brains of hoverflies process multiple, complex factors to determine which flower they pollinate.
These included a combination of visual clues (colour, shape, size), flower scents (more than 96 volatile chemical compounds) and immediate environment (humidity, carbon dioxide). Also, there were subtle differences in the way, say, a Bengaluru hoverfly and a Swedish hoverfly judged the attractiveness of flowers.
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Crunching over a million data points, researchers made “artificial flowers” to test their hypothesis of attractiveness. The Sikkim lure (artificial flowers based on what Sikkim hoverflies “like”) worked equally well in Bengaluru and Uppsala; while the Bengaluru lures were “less attractive” to hoverflies from other places.
Dr. Olsson hazarded a guess: “In Sikkim, the Hoverfly is the major pollinator as bees do not thrive in high altitudes. Wild flowers developed ways to make them as universally attractive as possible. Whereas in tropical Bengaluru, flowers have a choice of pollinators and do not have to try hard to attract hoverflies in particular.”
During the study, the team realised that hoverflies were hard to find in urban Bengaluru, leading to the start of research to find the link to hoverfly populations and air pollution.
The study, said Dr. Olsson, can give insights on reversing the decline of wild pollinators, which are critical to the nearly $577 billion-worth of crops globally. “There is a thought on creation of pollination gardens and other spaces to revive pollinator populations. But these ideas cannot be broad-based, because what works for European insect pollinators will not work in India. Studying these differences will help,” she said.