Recent observation of a proliferation of Ranunculus trichophyllus Chaix. in high-altitude lakes of the Mount Everest Region

Large populations of the threadleaf water-crowfoot, Ranunculus trichophyllus, were discovered in several high-altitude lakes in the Himalayas of Nepal in which the species did not occur as recently as 1987. One of the study lakes, at 4760 m, is the highest altitude from which an aquatic angiosperm has been reported. A canonical discriminant analysis suggests that the key environmental factors differing between vegetated and non-vegetated lakes among a chain of five interconnected water bodies are length of the ice-free season, conductivity, non-volatile suspended solids, and bicarbonate. We believe, however, that an increased length of the ice-free season is likely the controlling factor in the recent invasion by Ranunculus trichophyllus. Its range expansion is likely a signal of a warming alpine climate in our study area.