Mapping wing morphs of Tetrix subulata using citizen science data: Flightless groundhoppers are more prevalent in grasslands near water

Abstract

Abstract The slender groundhopper (Orthoptera: Tetrigidae) Tetrix subulata (Linnaeus, 1758), like several other taxa of winged insects, has a long‐winged and a short‐winged form, the latter incapable of flight. The optimal habitat of T. subulata consists of wet meadows and flat shores, as they feed mostly on algae and mosses in damp, sun‐exposed, open patches. Contrasting hypotheses predict either short‐ or long‐winged morphs to be relatively more prevalent in optimal habitats. Previous investigations were limited in their spatial extent. To strongly increase the number of study locations, we obtained, through the Global Biodiversity Information Facility (GBIF), geo‐referenced observations made by citizen scientists in the Netherlands. We determined individuals' wing form based on photographs accompanying these observations and related wing‐form patterns to large‐ and medium‐scale landscape characteristics. Our analyses revealed that in grasslands near the major rivers, relatively more short‐winged individuals were found. In drier landscapes consisting of coniferous forests and heath on the higher sand areas, more long‐winged individuals were observed. Built‐up areas had no significant effect on the wing length. These patterns might be caused by the oogenesis‐flight syndrome or small‐scale spatial sorting, but the exact mechanism is yet unknown, as size‐dependency might also play a role. Although opportunistic observations are biased by where and when observers prefer to go, and by reporting probabilities varying between species groups, these biases are not likely to have affected our conclusions. Citizen science data appear to be suitable for analyses of spatial distribution and sorting of morphological types within species.