How much biodiversity is actually floating in the air above a forest?
Last summer we ran a tropical–temperate forest comparison using airborne environmental DNA (airDNA). Using identical airDNA protocols, we sampled forests at Barro Colorado Island (Panama), Gordon Gulch (Colorado), and Hubbard Brook (New Hampshire) to see how entire biological assemblages compare across biomes.
One striking result was simply how much DNA is present in forest air.
Each air filter, after 24 hours, captured enormous numbers of DNA molecules from multiple biological assemblages simultaneously.
• tens of billions of fungal nuclear ITS copies per filter
• hundreds of millions of arthropod mitochondrial COI copies
• hundreds of thousands of plant chloroplast trnL copies
• tens of thousands to hundreds of thousands of vertebrate mitochondrial COI copies
When we sequence this DNA, so much that was hidden about the ecosystem came to light.
For example, at BCI, arthropod assemblages are strongly dominated by Cecidomyiidae. But BCI isn’t unique: 79% of arthropod OTUs at Hubbard Brook were also Cecidomyiidae, whereas the drier forest at Gordon Gulch showed much lower dominance (~31%).
Also, temperate forests can exceed tropical forests in fungal richness. Despite lower fungal DNA concentrations in the air, Gordon Gulch exhibited 150% higher total fungal richness than BCI. Much of this diversity comes from xerotolerant fungi such as Pleosporales, which thrive in dry environments.
Because airDNA captures fungi, plants, arthropods, and vertebrates simultaneously, it provides a new way to compare entire ecosystems with the same sampling method. At comparable sampling effort, BCI still showed higher richness for some groups—for example ~90 vertebrate OTUs versus 54 and 28 in the two temperate forests.
At Jonah, we’re convinced that AirDNA profiles will become a powerful tool to not only inventory individual ecosystems and watch their assemblages change over time, but they will become indispensable tools for comparing ecosystems.
Even more importantly, adoption can begin tomorrow.