Predicting invasion potential and niche dynamics of Parthenium hysterophorus (Congress grass) in India under projected climate change

In an era of climate change, predictive distribution modelling and niche dynamics of invasive species can help in understanding current and future invasion potential. Parthenium hysterophorus (Congress grass), native to tropical America, is one of the world's worst weeds with huge ecological and economic impacts, including in India. Here we report the current and future potential distribution of P. hysterophorus in India under climate change scenarios and describe its niche dynamics. The results revealed that under current climate, 65% of the total area in India is suitable for its potential invasion with three invasion hotspots identified: Western Himalaya, North-East and parts of Peninsular India. The study predicts an overall decrease in habitat suitability for this invasive species under climate change with about half of the suitable habitat reduced under RCP 8.5-2070; but some of the currently invaded regions will remain equally (North-East) or become highly vulnerable (Western Himalaya) to its invasion under future climate. Interestingly, niche dynamics results revealed that P. hysterophorus has shifted its climatic niche in the invaded range in India, more due to niche unfilling. Based on univariate analysis, niche dynamic processes in the analogous (expansion) and non-analogous (abandonment and pioneering) environments were also evident. The results from present study can help in developing climate change-integrated and region-specific invasion management strategies in India. More importantly, results of niche dynamics between native and invaded ranges of P. hysterophorus offer novel insights to understand the nature of niche shifts in invasive species and to predict the invasion potential under climate change.