Tracing aphid infestations through wood anatomical markers: Insights from Rhododendron campanulatum D.Don of the Himalayan region

Abstract

Recent climatic shifts have led to a noticeable increase in temperatures across the high-altitude ecosystems of the Himalayas, particularly in winter. This warming is altering growing conditions for many species, including aphids, found at higher altitudes where they were previously rare. As air temperatures increase, aphids develop more rapidly, extending their active periods and winter survival, and changing their geographical distribution and abundance. In this study, we analyzed the anatomical structure of Rhododendron campanulatum D.Don tree rings to detect aphid infestations in the higher elevational range of the Himalayas. Microscopic examination of wood sections from branches and increment cores from the main trunk revealed sapwood alterations caused by aphid activities. Our findings indicate that aphid activity was observed at elevations ranging from 3100 to 3400 m a.s.l., with a marked preference for younger trees (≤ 22 years) over mature ones (> 22 years) beyond a certain developmental stage. This suggests that aphid infestations are significantly more frequent and severe during the early life stages of the host trees, highlighting a vulnerability in younger individuals that diminishes with age. Hence, the pattern of aphid infestation is influenced not solely by rising temperatures, as previously assumed, nor is it significantly affected by altitude changes. Instead, it is notably impacted by the age of the samples. These anatomical markers highlight the impact of aphids and broader ecological shifts affecting plant resilience and forest health. Thus, this study urges collaboration among wood anatomists, entomologists, and ecologists to understand aphid life cycles, host preferences, and ecological interactions in the Himalayas. These findings are crucial for biodiversity conservation in the region and could affect ecological management strategies in other mountain regions worldwide.