The role of landscape connectivity in assembling exotic plant communities: a network analysis

Abstract

Landscape fragmentation and exotic species invasions are two modern-day forces that have strong and largely irreversible effects on native diversity worldwide. The spatial arrangement of habitat fragments is critical in affecting movement of individuals through a landscape, but little is known about how invasive species respond to landscape configuration relative to native species. This information is crucial for managing the global threat of invasive species spread. Using network analysis and partial Mantel tests to control for covarying environmental conditions, we show that forest plant communities in a fragmented landscape have spatial structure that is best captured by a network representation of landscape connectivity. This spatial structure is less pronounced in invasive species and exotic species dispersed by animals. Our research suggests that invasive species can spread more easily in fragmented landscapes than native species, which may make communities more homogeneous over time.

Drivers of Vegetation Species Diversity and Composition in Urban Ecosystems

“…The abiotic environment in urban areas may be more easily invaded, due to increased nutrient availability, human-aided transport of materials and propagules across the landscape, and the fragmentation of habitat. Habitat edges, which increase in proportion to habitat interiors as fragmentation increases, are zones of contact between contrasting patches, often share characteristics of both bordering patches, and can alter the rate of flux of species and materials, compared to habitat interiors (Cadenasso et al 2003;Minor et al 2009). For example, plants with winddispersed seeds tend to be less common in urban areas than in surrounding rural landscapes, because fragmentation of habitat makes it more difficult for seeds to arrive in favorable patches for germination (Cheptou et al 2008;Knapp et al 2012).…”

The effect of spatial configuration of habitat capacity on β diversity

“…By contrast, lower connectivity can isolate habitats, leading to lower a diversity but higher species turnover (i.e., higher b diversity; Hubbell 2001, Economo and Keitt 2010, Carrara et al 2014. Although the influence of landscape connectivity for community composition is widely appreciated (Chase and Ryberg 2004, Chave and Norden 2007, Minor et al 2009), few studies have considered the sole effect of habitat spatial configuration on b diversity.…”

Landscape corridors can increase invasion by an exotic species and reduce diversity of native species

“…This may be because invasive species often have high dispersal capabilities (Bufford and Daehler 2011), as is the case with the monogyne form of fire ants. Given that species with strong movement capacities are typically not dispersal limited, corridors are unlikely to facilitate their spread; indeed, landscape connectivity appears generally more important for native than for invasive species (Damschen et al 2006, Minor et al 2009). Some invasive species, however, have inherently poor dispersal abilities but spread well through accidental human transport (Mack and Lonsdale 2001;e.g., polygyne fire ants [Tschinkel 2006, King et al 2009] and Argentine ants [Linepithema humile; Suarez et al 2001]).…”

“…Yet, invasive species are not uniformly strong dispersers and it is possible that corridors may differentially affect their spread, depending on the capacity of each species for movement. Recent work suggests that species traits and behaviors related to movement are important for predicting species responses to altered landscape configuration, including the presence of corridors (Damschen et al 2008, Minor et al 2009, Sullivan et al 2011. We examine how differences in dispersal behavior of two social forms of invasive fire ants influence their use of corridors and their subsequent impacts on native ant diversity.…”