Researchers at Portland State University have made a surprising discovery: Little critters called springtails are helping moss have sex on Portland rooftops.
In a study published in the journal Nature, PSU scientists explain that so-called “rooftop moss” is using a variety of scents – just like flowers – to attract springtails and boost their sex lives.
People can’t smell these scents, but the tiny white springtail and new high-tech lab instruments can.
“We were extremely surprised to find such an amazing array of scents in female mosses,” said Sarah Eppley, lead author of the study. “Finding that the springtails were in fact acting like pollinators means we must totally rethink our understanding of plant-animal interactions in moss ecology.”
Eppley said the lab tests show the moss scents have compounds similar to floral and fungal smells.
Scientists had thought that water did most of the work in transferring sperm from a male moss to a female. But according to Eppley it’s both. Either water or critters can do the job, but moss reproductive rates are higher when both methods are used.
You can see a springtail if you look closely, Eppley said. The Northwest has a lot of them – up to 100,000 in a square meter.
“If you go hunting around in leaf litter or moss, you’ll see them,” she said. “They’re smaller than a grain of rice white, and they hop around. We have so much leaf litter in the Northwest that we have more of these arthropods than almost anywhere else.”
Eppley studies how moss grows in extreme environments, from Volcanic National Park to more local sites – like Portland’s roofs.
“One of the field sites was my neighbor’s rooftop,” she said.
She said the discovery that moss are basically using pollinators to reproduce raises a whole new hypothesis about how plants evolved to live on land.
“If this occurs in many species of mosses, that suggests it goes back to early lineages and that this could have helped getting plants established onto land,” said Eppley.
It could also fit into ongoing research about why there aren’t as many mosses in Portland’s Forest Park than there are in trees outside the city.
“When you’re way up outside the city you find huge amounts of moss, and you bring them in and find lots of mites and springtails,” she said. “But when you get into Forest Park you see much less diversity. We don’t know what that means yet.”