Trait distribution in Geometrid moth assemblages does not vary along a western Himalayan elevational gradient

Abstract

Elevation gradients pose challenges for flying insects due to temperature and air density shifts, impacting their thermoregulation, flight abilities and subsequently species distribution patterns. Geometrid moths are a model group for studying these traits among insects. This study examines how trait-patterns and niche differentiation of Geometrid moth assemblages change with elevation. Investigating 697 specimens of 120 Geometrid moth species, I assessed species diversity, turnover, and various traits related to body size and flight capabilities along a 1500m elevation span in the western Himalayas. Results indicate a decline in species diversity along the elevational gradients, accompanied by consistent turnover from lower to higher elevations. Despite this pattern, elevation did not significantly influence morphological traits related to thermal sensitivity (body size) and flight capability (wing loading and manoeuvrability) at the assemblage level in Geometrid moths. Furthermore, there was no significant niche differentiation among species across elevations. This supports the argument that species with similar ecological roles persist through turnover, maintaining consistency in trait values across assemblages. These findings from the paleotropics align with patterns observed in Geometrid moths across neotropical and temperate regions, highlighting the importance of trait-based approaches in understanding species responses to environmental changes. Summary StatementThis study examines how Geometrid moth assemblages in the western Himalayas respond to elevational gradients, revealing consistent turnover, stable traits, and no significant niche differentiation, emphasizing trait-based species adaptation