Modelled distribution of an invasive alien plant species differs at different spatiotemporal scales under changing climate: a case study of Parthenium hysterophorus L.
Predicting the impact of climate change on species distribution at different spatial and temporal scales has emerged as one of the important areas of research in invasion ecology and conservation biology. We used MaxEnt (Maximum Entropy Algorithm) to predict the distribution of a highly invasive species, namely Parthenium hysterophorus L. under four Representative Concentration Pathway scenarios (RCPs 2.6, 4.5, 6.0 and 8.5) in 2050 and 2070 at global (world), regional (India) and local (Jammu & Kashmir State) spatial scales. Model predictions indicated differences in the extent of expansion in the distribution of this species under different climate change scenarios with marginal increase in moderately suitable area at the global scale but mostly a declining trend was noticed in its suitable and highly suitable area in future. More or less similar trend was predicted for India where increase in moderately suitable area was evident but decline in suitable and highly suitable areas was observed. In respect of Jammu & Kashmir, moderately suitable as well suitable area showed increase mostly under RCP scenarios of 6.0 and 8.5 in 2050 as well as 2070. Further analysis revealed that current centroid of P. hysterophorus is in south of Jammu and Kashmir and is predicted to shift by an average of 20.48 km in the north-west direction by 2050 and by 36.83 km by 2070. The future suitable area is likely to be around Hirapora Wildlife sanctuary in Kashmir. Pairwise comparison of the niche overlap and dynamics of P. hysterophorus between the native Americas and each of the regions (Africa, Asia, Australia and Oceania) where the species is introduced using Schoener's D revealed variations in the niche overlap which was high between native Americas and Australia (0.70) and Africa (0.69), moderate between Americas and Asia (0.59) and low between Americas and Oceania (0.24). Exclusion of 25% of rare climatic conditions did not have any effect on the niche overlap index (D). Niche similarity test was not significant for any of the pairwise comparisons of native Americas and the continents in which the species is non-native indicating that the native niche is more similar to the exotic niche than any randomly sampled niche from the exotic range. But the niche equivalency tests showed that the environmental realized niche of P. hysterophorus in its invaded range was not totally equivalent to that in the native range indicating niche differentiation. The niche dynamic indices based on analogous and the entire climatic space in the native and introduced regions revealed a very high niche stability. A very limited niche expansion was noticed only in Asia and niche unfilling was evident in Oceania. Like niche overlap index (D), niche expansion and niche stability were not affected by the exclusion of 25% of rare climatic conditions but marginal change was noticed in niche unfilling in the Oceania. The above predictions have implications for formulation of policies at local, regional and global level for the management of this invasive species.