Parasitoid insects unveil complex patterns of functional change across elevational bands.

Climate change is rapidly reshaping how insects interact with their environment, potentially disrupting ecosystem complexity and essential functioning. While functional homogenisation has been extensively investigated for charismatic insect taxa, particularly pollinators, the response of parasitoids remains largely overlooked. Parasitoid insects exhibit drastically distinct life stages, with parasitic larvae and free-living (often nectarivore) adults, meaning that global change can have differential impacts on their functional diversity depending on the life stage. Here, we estimate multiple metrics of functional diversity for European bristle flies (Diptera: Tachinidae), a widespread parasitoid group, using traits measured in both larval and adult stages. We test how functional diversity metrics of larvae and adults vary through time and elevation, to uncover the extent and breadth of functional homogenisation. Our results show a progressive reduction in functional specialisation at high altitudes, for both larval and adult stages, revealing a decreased uniqueness of mountaintop biota. This pattern emerges from the upshift of generalist species, which dilute specialist species from mountaintops and make these areas functionally similar to lower elevational bands. This process determines a temporary increase in functional richness at high elevation, but may anticipate the loss of specialised ecosystem functions if generalists will eventually outcompete specialists. This can have remarkable effects on ecosystem stability, affecting parasitoids’ ability to control herbivore insects and pollinate flowers. Our results offer insights into the complexity of climate-driven change in functional diversity patterns, with increased functional richness in parasitoid assemblages associated with an overall trend of functional homogenisation. Supplementary Material File (fdiv.bristleflies_ecography.docx) - Download - 384.71 KB Information & Authors Information Version history Copyright This work is licensed under a Non Exclusive No Reuse License.

Authors Metrics & Citations Metrics Article Usage 147views 79downloads Citations Download citation Michela Gabrieli, Lara Marcolin, Luca Santini, et al. Parasitoid insects unveil complex patterns of functional change across elevational bands.. Authorea. 30 March 2026. DOI: https://doi.org/10.22541/au.177486902.26355844/v1 DOI: https://doi.org/10.22541/au.177486902.26355844/v1 If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download. For more information or tips please see 'Downloading to a citation manager' in the Help menu.