The species that move away from their native areas, either accidentally or deliberately, are alien species (Pysek et al. 2004). These alien species, which include both plants and animals, are invasive alien species due to their high reproductive rate and the potential for rapid spread over the large areas (Lowe et al. 2000, Pysek et al. 2004). The rapid spreading of invasive alien plant species (IAPS) is increasing especially on various land uses in the context of a changing climate (Meyerson and Mooney 2007) and infrastructure development such as road and transportation (Adhikari et al. 2020). In addition, the spreading of IAPS has escalated with globalization, through trade, tourism, travel and other human disturbances or activities (Lahkar et al. 2011), which are particularly conducive to IAPS (Mack et al. 2000, Knight et al. 2009). Furthermore, many tourism-related activities had contributed to the distribution of IAPS (Pathak et al. 2021). In particular, the promotion of tourism in protected areas like Chitwan National Park has substantially increased human activities in these areas, leading to the rapid spread of IAPS into these protected area (Pathak et al. 2021). In addition, various non-native species are intentionally introduced outside of their natural range to enhance tourism (Arismendi and Nahuelhual 2007). For example, sports fish species such as salmon and trout are introduced into non-native habitats to strengthen the possibilities of recreational fishing (Arismendi and Nahuelhual 2007).
Typically, IAPS tend to produce a large number of viable seeds (Brooks et al. 2004), and exhibit early sexual maturity (Pysek et al. 2003). This strategy reduces competition from native species and enhances the survival chances of IAPS (Mack et al. 2000, Knight et al. 2009). Moreover, the IAPS can cause remarkable negative impacts on native flora and fauna (Mooney et al. 2005, Hardesty-Moore et al. 2020). These impacts include the loss of native species and biodiversity (Kohli et al. 2006), habitat alteration (Murphy et al. 2013), and the deterioration of ecosystem productivity and nutrient cycling (Charles and Dukes 2008, Vila et al. 2011). After the several generations, the IAPS are capable of adapting to their introduced habitat (Baker 1986). This adaptibility is facilitated by their ability to adjust to new climatic conditions (Hellmann et al. 2008), which can lead to negative impacts on the ecosystem (Vila et al. 2011, Shrestha and Shrestha 2021). Several studies had demonstrated that IAPS, such as Parthenium, exhibit allelopathic nature due to the presence of water soluble phenolic and sesquiterpene lactones like parthenin (Timsina et al. 2011). This leads to the inhibition of the growth of other plants through the soil contamination (Belz et al. 2007, Rashid et al. 2008). Consequently, IAPS become dominant in the introduced habitat (Khaniya and Shrestha 2020).
In certain localities, some IAPS are used for food, medicine, fuel, or fodder as a means of control (Kull et al. 2007). For examples, silver wattles (Acacia dealbata), black wattles (A. mearnsii) and green wattles (A. decurrens) are used globally for economic, environmental and ornamental purpose (Kull et al. 2007). Sometimes IAPS have been used as alternative sources of fodder for livestock (Shrestha et al. 2018). Despite their potential areas, IAPS have negative impact on agricultural production, forest regeneration (Shrestha et al. 2018), livestock grazing (Lahkar et al. 2011, Khaniya and Shrestha 2020), and human health (Rai and Singh 2020). For example, the Indian Muntjac (Muntiacus muntjak) in Baluran National Park, Java, was found to avoid IAPS invaded habitat (Tyson 2007).
Biological invasions can have impacts on pollinator communities, as they attract pollinators and dispersers away from native species (Aravind et al. 2010). For example, the berries of lantana (Lantana camara) attract frugivorous birds and mammals, leading to the dispersal of its seeds and hindering the reproductive success of native species (Aravind et al. 2010). Although Nepal provides habitats for species from various parts of the world due to physiographic and climatic variation (Brown et al. 2002; Chaudhary et al. 2020), the effects of IAPS invasion have been limited. Therefore, we aimed to assess the abundance of IAPS and their effects on the occurrence and habitat utilization of threatened mammal species in Shuklaphanta National Park, Nepal. These data will be immensely helpful for the park managers devising a robust management strategy for controlling the invasive.