SUR study: High-altitude flies, guardians of climate-threatened biodiversity

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. This is the conclusion of 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.

Moreno Di Marco, Head of the Biodiversity & Global Change laboratory at Sapienza University and study Coordinator - © archiviofotografico_Sapienza

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.

Meet the bristle flies

One of these species is the Bristle flies or tachinid flies - 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, 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", says Pierfilippo Cerretti, Director of the Museum of Zoology and senior author of the study.

The specialists have analysed the data of more than 60,000 museum specimens of bristle flies collected in Europe from 1845 to the present day. Luca Santini, the co-author of the study, explains: "the decline observed in high-altitude specialist flies implies an increased risk of the spread of herbivorous insects, which could reshape mountain ecosystems".

And Moreno Di Marco, head of the Biodiversity & Global Change laboratory at Sapienza University and study coordinator, concludes:

The data highlighted by our work 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.

Find out more by reading the original sotry, in Italian.