Host use diversification during range shifts shapes global variation in Lepidopteran dietary breadth

Area of Science:

• Ecology
• Evolutionary Biology
• Zoology

Background:

• Niche breadths often increase with latitude, commonly attributed to local adaptation along environmental gradients.
• Evidence for increased benefits of generalization at higher latitudes remains inconclusive.

Purpose of the Study:

• To test the hypothesis that latitudinal niche breadth variation is a non-adaptive outcome of range shift dynamics.
• To investigate the drivers of broader diets observed at higher latitudes in Lepidopteran species.

Main Methods:

• Analysis of a global dataset of 6,934 dietary records from 4,410 Lepidopteran species.
• Correlating population-level dietary niche breadths with geographic range position and poleward range extent.

Main Results:

• Diet breadth is better explained by proximity to poleward range limits than by observation latitude.
• Species with higher poleward range extents and those undergoing rapid range shifts exhibit broader diets.
• Latitudinal variation in diet breadth is more pronounced in species with dynamic ranges.

Conclusions:

• Latitudinal niche breadth patterns are likely transient, emergent properties of recent range dynamics, not necessarily adaptive responses.
• These findings have implications for understanding ecological changes and host use shifts in species on the move.