Why native mountain grasshopper populations grow to different sizes

Embargoed until: Publicly released: 2026-03-11 11:01

New Zealand

PHOTO: Steve Trewick

Research on flightless native grasshoppers found only on the Southern Alps shows that their size is linked to both their environment and whether they can breed with other grasshopper populations. Scientists measured over 800 grasshoppers at six mountains spanning 670 km, from Tasman to Queenstown Lakes. Their sizes didn't depend on how high up the grasshoppers lived, but populations living on different mountains did vary in size. The authors suggest this is because grasshoppers on the same mountaintop at different elevations can breed and mix their genes, but the groups isolated on each mountain adapt to local conditions.

News release

From: The Royal Society

Why do mountaintop grasshoppers grow to different sizes in different places? Our research shows this partly depends on how freely grasshoppers can move and mix between populations. Populations that are isolated can evolve different body sizes, likely shaped by local environmental conditions. We found that closely related species sharing the same landscape displayed different patterns of body size, and even males and females within a single species can evolve differently. Our analysis highlights the role of gene flow in constraining evolution.

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Single female Sigaus nitidus

Pair of Sigaus nivalis

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Journal/
conference: Royal Society Open Science

Research:Paper

Organisation/s: Massey University

Funder: This research was assisted by grants from the Miss E. L. Hellaby Indigenous Grasslands Research Trust and Orthopterists’ Society’s Theodore J. Cohn Research Fund, and a doctoral scholarship from Massey University (awarded to F.L.M.-J.). Open access publishing facilitated by Massey University, as part of the Royal Society–Massey University agreement via the Council of Australian University Librarians.

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