Recently, Mark Johnson, a graduate student within Texas Tech's Department of Natural Resources Management, was featured in an article by Elizabeth Pennisi, a senior correspondent covering aspects of biology for the AAAS's Science Journal. Here's part of the takeaway.

Inventorying the plants in a tract of woods or fields or searching for invasive species can take days of hot, hard work slogging through thorny brush and tick-infested grass. Now, researchers have shown that simply capturing and analyzing the DNA plants release into the air can work as well as putting boots on the ground—and in some cases even better.

Plants already emit airborne tracers that are familiar to anyone with allergies: windborne pollen. The grains' distinctive shapes make it possible to identify unseen species simply by capturing their pollen. But pollen surveys have their limits. They only detect pollen that's spread by wind (other types depend on pollinating insects and other animals), require well-trained experts, and don't always produce species-specific identifications. 

Mark Johnson, a doctoral candidate in Texas Tech's Department of Natural Resources Management, wanted to know whether studying the eDNA shed into air as pollen or in minuscule fragments of leaves or flowers would work better. The Pennsylvania native and a research team that included NRM faculty Robert Cox and Matthew Barnes, along with Mohamed Fokar, a research associate professor with Tech's Center for BioTechnology Genomics, developed better ways to collect plant eDNA in dust traps, and in 2019 they demonstrated that the filters capture DNA-bearing traces from all sorts of plants.

“We could find species not flowering, not pollinating, or when they are not active like in the winter,” Johnson said.

Now, he has shown how eDNA can inventory an entire plant community. Johnson and his colleagues mounted dust traps in nine places across a well-studied short grass prairie on Texas Tech native rangeland. They collected the dust every couple of weeks for one year, extracted the DNA, and sequenced a gene that varies among plant species, serving as a “DNA barcode” for identifying them. In the spring and again in the fall, his team also pulled on their boots and surveyed plants along 27 100-meter transects. They compared the results of the two kinds of surveys.

The traditional surveys detected 80 species and the air eDNA study 91, the team reported. Both surveys uncovered the same 13 grass species, but the eDNA work found an additional 13. Among nonwoody flowering plants, both approaches yielded a total of 60 species, but each detected 20 or so that the other missed. eDNA was better at finding easily overlooked species with small flowers, such as weakleaf bur ragweed. But people were better at spotting plants too rare to release much eDNA, particularly when they had showy flowers, such as the chocolate daisy.

CONTACT: Warren Conway, Chair, Department of Natural Resources Management, College of Agricultural Sciences and Natural Resources, Texas Tech University at (806) 834-6579 or warren.conway@ttu.edu

0111NM22 /Editor's Note: For a full-text version of Elizabeth Pennisi's Science article, please click here