A major experiment that utilized computerized “evolving” artificial flowers solved an evolutionary puzzle. Many flowers produce diluted nectars even though bats, their main pollinators, prefer sugary substances. The research team found that bats had less preference for sugar than previously believed. Most bats were instead more concerned about finding any kind of food. The findings are in a paper that was just published in the journal Science.
Bats are important pollinators of many flower species, especially varieties that bloom at night. Oddly, most of these flowers produce diluted nectar even though bats are attracted to sugar. This doesn’t make evolutionary sense—if the flowers rely on bats for pollination, why wouldn’t they produce sugary nectar?
A team of scientists designed an experiment to determine why bat-pollinated flowers have evolved to produce diluted, less sugary nectar. The team set up artificial flowers in a Costa Rican rainforest. The flowers contained synthetic nectars and were connected to a computer. As bats visited the flowers, a computer program simulated how the flowers would have evolved over years. When a flower was frequented by several bats, for example, it would reproduce more often in the computer simulation. The researchers tagged bats with radio transmitters to better track how their feeding behaviors were affecting flower evolution.
The team made a surprising finding—the bats weren’t all that picky about sugar concentrations. While they preferred sugar in small experiments, they became less choosy as the overall bat population increased. When there were many bats in the area, individual bats consumed any nectar they came across, regardless of sugar concentration. This resulted in flowers that “evolved” to produce diluted nectar, allowing them to feed more bats. Although bats clearly prefer sugar, they can’t afford to be picky when competing with their colony.
The team’s findings provide new insights into the evolutionary dynamics between flowers and their pollinators. Many flowers evolved to produce diluted nectar because bats show little preference when food competition is high. Similar experiments with computer simulations may help researchers solve more evolutionary puzzles in the future.
Nachev et al. Cognition-mediated evolution of low-quality floral nectars. Science (2017).