Identifying hotspots and climate drivers of alien plant species for conservation prioritization across the Pan-Himalaya

Identifying and understanding the distribution characteristics of alien plant species in relation to climatic variables is a crucial prerequisite for native biodiversity conservation. We analyzed the spatial distribution of 1857 alien plant species with 72,722 distribution records across the Pan-Himalaya. The species-level phylogenetic tree demonstrated a well-resolved evolutionary relationship across the taxa. By utilizing the spatial phylogenetic approaches, we found that areas of western Himalaya and eastern Himalaya exhibited relatively high species richness (SR) and phylogenetic diversity (PD). The analyses on relative phylogenetic diversity (RPD), standardized effect size of PD (SES.PD), net related index (NRI), and nearest taxon index (NTI) highlighted that alien plant species were clustered phylogenetically in western and eastern Himalaya. By using the spatial overlap of SR and PD, we identified ten hotspots, of which six were identified as conservation gaps. Moreover, the SR and PD are not significantly different in protected and not-protected areas. The structure equation model (SEM) demonstrated better goodness-of-fit (R-2) between all variables with SR (Adj R-2 = 0.63) and PD (Adj R-2 = 0.66). Specifically, anthropogenic activities with Adj R-2 of >90 % for both SR and PD were the dominant variables influencing alien plant species in the Pan-Himalaya. Temperature was the next key variable, with Adj R-2 at >89 % for SR and 87 % for PD. This study provides advancement in identifying hotspots of alien plant species and facilitating informed management of conservation strategies to protect the indigenous flora of Pan-Himalaya.