Elevational variation in trichomes of the alpine subnival woolly plant Eriophyton wallichii: Abiotic and biotic correlates and impacts on other traits.

Abstract

Background and aims: Research has extensively examined how adaptations to extreme environments shape the highly specialized phenotypes of alpine subnival plants; however, large-scale biogeographic patterns of these specialized plant phenotypes remain largely unexplored.

Methods: This study investigated the elevational patterns of leaf trichome density in the alpine subnival woolly plant Eriophyton wallichii, alongside its abiotic and biotic correlates, as well as the effect of trichome variation on chemical defence and chlorophyll content. We sampled 11 populations of E. wallichii spanning an elevation range of 4000-4800 m a.s.l., covering most of this species' altitudinal distribution and exhibiting significant variation in abiotic conditions, plant traits, and leaf herbivory.

Key results: Our results revealed significant variation in leaf trichome density among populations, with a notable increase at higher elevations. This elevational trend was strongly negatively associated with the mean temperature during the growing season and, to a lesser extent, positively associated with leaf herbivory. In contrast, precipitation and solar radiation during the growing season showed minimal influence on trichome variation. Interestingly, phenolic compound concentrations in leaves decreased with increasing trichome density, whereas leaf chlorophyll content remained unchanged.

Conclusions: Our results indicate that adaptation to low temperatures is a key driver in the evolution of woolly plant phenotypes in alpine subnival environments, highlighting potential consequences for these adaptations under global climate change and species distribution shifts. Additionally, the trade-off between trichome density and chemical defences may have significant implications for plant survival strategies in resource-limited environments. Our data also suggest that biotic interactions, especially those involving herbivores, may play an important role in shaping the adaptive mechanisms of some alpine subnival plants.