A look inside the stomachs of carnivorous plants

Researchers from Curtin University, the Botanical and Zoological Natural History Collections in Munich and the Ludwig Maximilian University of Munich have found a way to take a sophisticated look inside the stomachs of carnivorous plants, overcoming a hurdle that had previously stumped entomologists. Their work has been described in the journal Scientific Reports.

Lead author Thilo Krueger, a PhD student at Curtin, explained that many carnivorous plant species are critically endangered, threatened by habitat destruction, environmental pollution and climate change. It is critical to their survival for scientists to understand exactly how many and what kind of insects carnivorous plants eat.

“Quite often, several carnivorous plant species are found in one habitat, and the question arises if different species may rely upon different food sources,” he said. “To develop conservation plans that protect their future, it is essential to understand their biology, which includes what they eat — their natural prey spectra.

“Studying the prey spectra of carnivorous plants has previously been hampered by the fact that digested insect prey is often hard to identify, even by trained entomologists. Soft-bodied insects such as midges often turn into unidentifiable crumbs during digestion on the leaves.”

Co-author Dr Adam Cross, also from Curtin, said the new method combines macro photography of the captured insects with DNA metabarcoding, a cutting-edge insect identification tool. He explained, “Any insect that is captured by a carnivorous plant will contain traces of its genetic material or DNA, even after digestion by the plant. This DNA can be detected and compared with DNA libraries of known insects, thus identifying the prey.

“Because DNA metabarcoding is prone to contaminations and does not allow us to estimate the quantity of prey, we carefully controlled our data using macro photographs of the prey items to achieve an unprecedented completeness of prey spectra data.”

Senior author Dr Andreas Fleischmann, from the Botanical Natural History Collection and the University of Munich, said the new method of DNA metabarcoding was so sensitive that it even detected tiny amounts of insect DNA that were not obvious to researchers from field examination and macro photographs.

“Hence, our study of carnivorous prey spectra using genetic DNA fingerprints from the captured insects resembled reconstructing a crime scene — except our crime scene investigation was about finding out what a set of carnivorous plants had for lunch,” Dr Fleischmann said.

Image credit: Thilo Krueger.

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