Invasion in a heterogeneous world: resistance, coexistence or hostile takeover?

Abstract

We review and synthesize recent developments in the study of the invasion of communities in heterogeneous environments, considering both the invasibility of the community and impacts to the community. We consider both empirical and theoretical studies. For each of three major kinds of environmental heterogeneity (temporal, spatial and invader-driven), we find evidence that heterogeneity is critical to the invasibility of the community, the rate of spread, and the impacts on the community following invasion. We propose an environmental heterogeneity hypothesis of invasions, whereby heterogeneity both increases invasion success and reduces the impact to native species in the community, because it promotes invasion and coexistence mechanisms that are not possible in homogeneous environments. This hypothesis could help to explain recent findings that diversity is often increased as a result of biological invasions. It could also explain the scale dependence of the diversity-invasibility relationship. Despite the undoubted importance of heterogeneity to the invasion of communities, it has been studied remarkably little and new research is needed that simultaneously considers invasion, environmental heterogeneity and community characteristics. As a young field, there is an unrivalled opportunity for theoreticians and experimenters to work together to build a tractable theory informed by data. KeywordsCommunity ecology, environmental heterogeneity hypothesis, impact, invader-driven heterogeneity, invasibility, spatial heterogeneity, spatial spread, temporal heterogeneity.Ecology Letters (2007) 10: [77][78][79][80][81][82][83][84][85][86][87][88][89][90][91][92][93][94] I N T R O D U C T I O NEarly theory for biological invasions treated the environment as if it were homogeneous in space and time (Skellam 1951). Similarly, few empirical studies of invasion directly address environmental heterogeneity, and experiments are designed to minimize its effects. In reality, invasions proceed in a highly heterogeneous world and in the context of existing communities of species. For example, important environmental drivers such as temperature, water, nutrients, sunlight and physical disturbances, are all variable at a range of spatial and temporal scales, as are the densities of species in the resident community. Recent developments in the theory of invasions suggest that environmental heterogeneity plays a defining role in whether the community can resist new invasions and the rate at which an invasion progresses. Heterogeneity is also likely to be an important factor in the outcome of invasions, changing the impacts on the community in the event of a successful invasion, including whether native species are driven to extinction and the extent to which species abundance patterns within the community are altered.In this review, we consider how environmental heterogeneity modifies the invasibility of the community and the impacts on the community following invasion. First, we define the key concepts and framework within w...

Climate modifies response of non-native and native species richness to nutrient enrichment

“…Increased nutrient addition and climate conditions, however, can have interacting effects on the success of non-native species [13][14][15]. These effects are influenced by how variation in the mean and heterogeneity of the local environment alters the persistence and establishment of taxa within communities, and the interactions within and among their populations [16]. Further, non-native species differ substantially in their ecological strategies [17,18], potentially leading to varying responses of non-natives to specific combinations of nutrient enrichment and climate conditions.…”

“…However, the interactive effects of climate mean and variability with nutrient addition on species diversity remain uncertain. Climate-based environmental heterogeneity could offset the negative effects of eutrophication on species coexistence via mechanisms such as the temporal storage effect [26][27][28], as different species in a community may be favoured at different points in time [16]. Alternatively, climate variability could interact with eutrophication to enhance species invasion by opening colonization windows for species with strategies for high-nutrient resource capture (i.e.…”

Linking environmental heterogeneity and reproductive success at single-cell resolution

“…At the scale of individual organisms, it affects the ability to survive, reproduce, co-exist and interact with other organisms. For plants and animals, environmental impact can be assessed and quantified relatively simply at the level of individual organisms (Melbourne et al, 2007). In microbial ecology, however, the effect of environmental variability on microbial activity and diversity is commonly assessed at a scale that is several orders of magnitude greater than the dimensions of the microorganisms under study (Hellweger and Bucci, 2009).…”

Persistence of structured populations in random environments

“…The effect of these interactions and fluctuations on an individual's fitness can depend on an individual's "state" such as its age, size, physiological condition, or location in space. Understanding how all of these factors influence population persistence is a fundamental issue in many areas of population biology including conservation biology (Caswell 2001), metapopulation theory (Hanski 1999), spatial spread of invasive species (Melbourne et al 2007), and evolution of life history traits (Charlesworth 1994).…”