Many wildflowers of spring in eastern North America bloom thanks to ants. The tiny six-legged gardeners have partnered with those plants and about 11, 000 others to spread their seeds. The plants, in turn, "pay" for the service by attaching a calorie-loaded appendage (附属物) to each seed, much like fleshy fruits remunerate birds and mammals that desert seeds or poop (排泄) them out. But there's more to the ant-seed relationship than that exchange, researchers reported last week at the annual meeting of the Ecological Society of America, which was held online.
Many ants eat seeds. Certain plants attach a nutritive globe called an elaiosome(油质体) to their seed coats, which serves as a favorite lunch for the ants' young and gives ants a handle on seeds that can be bigger than their heads. Until now, researchers assumed the ants simply carry the seeds to their nests, feed the elaiosome to their young, and deposit the seed either outside or inside at the colony's "garbage dump", which provides a rich environment for shooting.
In both the field and the lab, Chelsea Miller presented ants with seeds from various trillium (延龄花) species and found the ants were quick to pick up some species' seeds while leaving others to rot, Miller said. To find out how ants make their choices, Miller and Susan Whitehead at the Virginia Polytechnic Institute and State University (Virginia Tech) used techniques to analyze the chemical makeup of elaiosomes. They found that ants pick seeds based on the specific combination and concentrations of acid and other compounds made by the plant, 20 of which are unique to trilliums. The ants' tastes may affect plant species' distributions, says Kirsten Prior, an ecologist at Binghamton University: "Widespread trillium species are preferred by seed-dispersing ants compared to rare trillium species."
Melissa Burt, an ecologist at Virginia Tech, hopes these studies bring ants new respect. "Many people who talk about ants only know them as insects that are taking over their kitchens, but many ants perform important functions in ecosystems," she says. "Seed dispersal is just one of those."
