Climate change has a particularly significant impact on mountain biodiversity. Altitude species are often specialists, i.e. able to live in a restricted variety of environmental conditions (sometimes extreme), and are therefore also very sensitive to climate change.

Bristle flies or tachinid flies are parasitoid insects that 'exploit' other insects (especially caterpillars) at the larval stage, while they are free-living and feed on nectar as adults.

"In mountain ecosystems," says Pierfilippo Cerretti, Director of the Museum of Zoology and senior author of the study, "their role is crucial because they keep in check the populations of various herbivorous insects of which they are parasites. Some species show a preference for specific hosts, while others are broadly generalists".

A new study, published in the journal PNAS and conducted by the Charles Darwin Department of Biology and Biotechnology, in collaboration with Sapienza Museum of Zoology, analysed the data of more than 60,000 museum specimens of bristle flies collected in Europe from 1845 to the present day, showing that since the middle of the last century, the percentage of specialist bristle flies has increased by 70% at low altitudes and decreased by 20% at high altitudes, where generalist species have spread rapidly over the same period.

"The decline observed in high-altitude specialist flies," adds Luca Santini, co-author of the study, "implies an increased risk of the spread of herbivorous insects, which could reshape mountain ecosystems".

"The data highlighted by our work," concludes Moreno Di Marco, head of the Biodiversity & Global Change laboratory at Sapienza University and study coordinator, "show an effect of climate change that goes beyond individual species, suggesting that the entire composition of ecosystems is rapidly changing with potentially enormous repercussions on mountain biodiversity".

The results of this study also show how the heritage of natural history museums, obtained through field collection campaigns and long-term monitoring plans, is fundamental to the understanding of complex, and most topical, natural phenomena such as climate change.

References:

Elevational homogenisation of mountain parasitoids across six decades – Moreno Di Marco, Luca Santini, Daria Corcos, Hans-Peter Tschorsnig, Pierfilippo Cerretti – Proceedings of the National Academy of Sciences (2023). https://doi.org/10.1073/pnas.2308273120

Further Information

Moreno Di Marco
Department of Biology and Biotechnology Charles Darwin
moreno.dimarco@uniroma1.it

Pierfilippo Cerretti
Department of Biology and Biotechnology Charles Darwin
pierfilippo.cerretti@uniroma1.it