Climate warming may erode thermal barriers to pest invasion in tropical alpine ecosystems: Evidence from the Andes

Abstract

Climate warming is increasingly enabling species to cross bioclimatic barriers, driving altitudinal range expansions of species and facilitating biological invasions into ecosystems that were historically protected by low temperatures. Among these cold ecosystems are tropical alpine systems—páramos—found in the tropical Andes above 3000 m elevation. Páramos play a critical role in water provision, carbon storage, and biodiversity conservation and harbor numerous endemic plant species with narrow distributions, making them highly susceptible to climate change and biological invasions. However, empirical evidence linking climate warming to the thermal performance and potential establishment of pest species in these ecosystems remains scarce. Here, we combine molecular identification, experimental thermal assays, and occurrence‐record analyses to assess whether the thermal performance and recorded elevational distribution of a pest species are consistent with its potential establishment in páramo ecosystems. We investigated recent episodes of sustained herbivory on the endemic plant Paepalanthus alpinus , caused by an unidentified larva in the Matarredonda páramo in the northern Andes of Colombia. Using DNA barcoding cytochrome c oxidase subunit I (COI) and phylogenetic analyses, we identified the larva as Mythimna unipuncta (Lepidoptera: Noctuidae), a cosmopolitan crop pest not previously reported from tropical Andean alpine environments. To evaluate whether warming may be consistent with its establishment, we assessed larval survival and development under 3 day/night temperature regimes (30/20°C, 25/15°C, and 20/10°C) spanning current warm‐day conditions recorded in the páramo and experimentally warmer regimes designed to assess thermal performance and upper tolerance limits. Optimal development occurred at 25/15°C, conditions that exceed historical páramo temperatures prior to recent warming trends. However, survival declined at the highest temperature treatment, indicating upper thermal limits. An expanded analysis of public occurrence records, combined with our own records, showed that the annual maximum elevation of recorded M. unipuncta occurrences has increased during the modern period. Together, these findings provide convergent distributional and experimental evidence that warming may relax thermal constraints on pest establishment in páramos and may facilitate the use of high‐elevation tropical environments by M. unipuncta . More broadly, our results highlight the vulnerability of cold, highly endemic tropical alpine ecosystems to climate‐facilitated biological invasions.