Phenotypic plasticity: Cause of the successful spread of the genus Potamogeton in the Kashmir Himalaya

• Morphology differs across lentic and lotic waters for species colonising both habitats.
• Transplantation reveals that these differences in plant traits are plastic.
• Phenotypic plasticity allows these species to inhabit a diverse range of habitats.

Morphological variations observed for a given species according to habitat conditions are generally associated with plant adaptation to local conditions enhancing the plants ability to occupy a wide range of environments, and hence ecological niche breadth. Morphological variations can result from genetic differentiation or from phenotypic plasticity in response to environmental conditions. The present study was undertaken to assess phenotypic variations in the most widespread, as well as one of the largest, aquatic genera of the Kashmir Himalaya. The study was conducted in 10 species of Potamogeton across habitats with different water flow types and a common garden experiment was carried out to test for the plastic origin for the morphological differences observed under natural conditions. Significant differences were observed in morphological characters such as the leaf dimensions, spike and peduncle length; and number of spikes, flowers, fruits and turions/tubers per ramet in both lentic and lotic waters. The results of the transplantation experiments revealed that when plants of the same species collected from different habitats (standing and running waters) were grown under similar conditions, the differences in the morphological traits were no longer observed at the end of the transplantation period. These results suggest that the morphological differences observed between the plants sampled under different conditions are due to phenotypic plasticity and not to genetic differentiation. The capacity of these species to colonise a wide range of environmental conditions may rely on this high level of morphological variation.