Ollier, S. | Search bioRxiv

bioRxiv2026

Beyond Gloger's rule: multiple biogeographic drivers of dark and red colouration in ants

Colour is a key trait involved in camouflage, physiological protection and thermoregulation. Yet environmental drivers of colour variation remain poorly understood at large spatial scales. Glogers rule predicts animals should be darker in warmer and wetter climates, and in a complex version, redder in warmer and drier climates. Here, we present the first test of the complex Glogers rule in insects using 34,331 images of 10,400 ant species across 586 assemblages worldwide. We decompose species mean colouration into two orthogonal axes, linked to darkness and redness. Assemblages were darker under high UV-B radiation and low dry-season precipitation, consistent with UV protection and desiccation resistance via melanisation. Canopy height increased both axes, suggesting camouflage. In contrast, higher mean temperature of the warmest quarter increased redness, as predicted by the complex Glogers rule. Ant colouration cannot be explained by one macroecological rule but reflects environmental drivers acting independently on darkness and redness.

ecology↗

bioRxiv2020

Long-distance dispersal of oilseed rape seeds: The role of grain trailers.

In agroecosystems, anthropogenic activities can modify the natural dispersal capacity of crops and their capacity to establish feral populations. In the case of oilseed rape (OSR), seed spillage from grain trailers during harvest was first quantified by an in situ scientific study (Selommes, Loir-et-Cher, France). Demographic analysis of seeds collected from 85 traps set on road verges suggested that OSR dispersal distance due to seed spillage from grain trailers can be up to 400m. In the present study, we used SSR markers to genotype seeds collected from trap-sites and from surrounding OSR fields to precisely estimate the distances between traps and fields. Trailer directions on each road were also considered. Few seeds (5.8%) were not linked to a field in the studied area, while most of the seeds (59.2%) were linked to a field situated over 400 m away. The overall mean dispersal distance was 1250 m. It ranged from 308 m to 1392 m for one-lane roads, and from 1048 m to 1404 m for two-lane roads. Events of seed dispersal at greater distances (> 5 km) were rare but still possible. It thus follows that OSR seed dispersal due to spillage from grain trailers should be carefully considered in the context of genetically modified plant cultivation.

ecology↗