Abstract
Identifying factors that underlie invasive species colonisation and change in density could provide valuable insights into the mechanisms of biological invasions and for invasive species management. We examined a suite of factors potentially influencing the landscape-level invasion of Lantana camara L., one of the most ubiquitous invasive species in South Asia. These factors included disturbance factors like forest fires, historical habitat modification, and edge effects, in addition to factors like propagule pressure and habitat suitability. We examined the relative importance of these factors on the colonisation and change in density of L. camara in the Biligiri Rangaswamy Temple Tiger Reserve, Western Ghats, India. We used extensive (1997–2008) datasets tracking the presence and abundance of L. camara and combined these with corresponding data on disturbances, propagule pressure, and habitat suitability. We used an information-theoretic model selection approach to determine the relative importance of each factor on the colonisation and change in density of L. camara. Colonisation was mainly a function of proximity to already established populations (i.e. propagule pressure), whereas increase in L. camara density appeared to be constrained by high fire frequency. Research and management efforts need to recognize the multidimensional nature of mechanisms underlying L. camara’s success during different invasion phases when strategizing interventions to mitigate its effects.
Highlights
The likelihood of an introduced species becoming invasive is determined by the interplay of the invader’s characteristics, the abiotic environment, and biotic interactions within novel environments (e.g. enemy-release; Keane and Crawley (2002))
Feedback loops between periodic disturbances and invasive species dominance have been observed in some systems, indicating the pivotal role played by disturbance in biological invasions
Camara neighbourhood index explained only 6.2% of the deviance from the interceptonly model for colonisation data, parameter averaging indicated that the L. camara neighbourhood index had the highest evidence of support as a predictor of colonisation when compared to all other covariates (Table 3)
Summary
The likelihood of an introduced species becoming invasive is determined by the interplay of the invader’s characteristics (e.g. its high propagule output; Sakai et al 2001), the abiotic environment ( disturbance; Shea and Chesson 2002), and biotic interactions within novel environments (e.g. enemy-release; Keane and Crawley (2002)). The disturbance regime prevalent in an area plays a pivotal role in influencing invasive species success (Davis et al 2000). Habitats that are subject to natural or anthropogenic disturbances could be vulnerable to invasion (Jauni et al 2014). In an experimental study using forest understory plants, von Holle and Simberloff (2005) found that successful invasions were contingent upon the number of propagules arriving in situ, when compared to other factors such as resident diversity and the flooding regime. In turn, is dependent upon life history characteristics such as time taken to reach reproductive maturity and dispersal mode – rapidly maturing species with abiotically dispersed seeds tend to be more successful compared to slow-maturing species with biotically dispersed seeds (Daehler 1998)
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