Phenotypic variation in morphology and associated functional traits in Ageratina adenophora along an altitudinal gradient in Kumaun Himalaya, India

Biological invasion not only depends on the environmental characteristics of any region but also on the fundamental characteristics of the invader species. Assessment of plant performance across diverse habitats and altitudinal gradients provide insights into the traits contributing to invasion success in addition to its habitat suitability, susceptibility and mechanisms adopted by the plant. As the environmental conditions of similar habitat types vary within short distance in mountainous landscapes, the present study was conducted with aim to understand the morphological and functional trait variations in a notorious invasive weed Ageratina adenophora along the altitudinal gradient in Kumaun Himalaya, India. The results revealed that due to higher plasticity in the plant traits, this weed can take advantage of available invasion windows. Morphological traits i.e. plant height (SL), root length (RL), above and belowground biomass (AGB and BGB), number of leaves (LN), branches (BN) and capitula (CN); functional traits i.e. root:shoot ratio (R:S ratio), root weight ratio (RWR), stem weight ratio (SWR), leaf weight ratio (LWR), inflorescence weight ratio (IWR) etc.; and seed output along an altitudinal gradient explained the invasion success of A. adenophora in diverse habitats. Plasticity of plant traits in diverse habitats signifies the strategies that assisted A. adenophora to become a successful invasive species. Higher biomass allocation to shoots favors speedy increase in plant height, an approach adopted by most of the plants for sunlight harvesting. Across the altitudes, healthier plant performance was recorded at mid altitudinal ranges (1000-2000 m a.s.l.), and among the habitats, good performance of A. adenophora in streamline, wasteland, wall and road-side populations in comparison to forest and cultivated land indicated vulnerability and further spread of A. adenophora in these habitats.