Effects of plant invasions on wildlife in desert grasslands

Abstract

Like all grasslands across North America, the distribution of desert grasslands has been reduced markedly, and remnants have been altered extensively by humans. In Arizona, New Mexico, Texas, USA, and in Mexico, desert grasslands have been invaded by dozens of non‐native plants, especially perennial grasses that evolved in arid systems with similar climate and disturbance regimes. In desert grasslands invaded by non‐native plants, biomass, richness, and diversity of native plants typically decrease, whereas plant density, biomass, and litter typically increase. These changes in composition and structure of the plant community affect animals that inhabit grassland ecosystems, with the direction and magnitude of effects reflecting the resource needs of each species, the degree of plant invasion, and the contrast in structure between invading and native plants. When non‐native plants present similar structural cues but provide different levels of resources than native plants, cues that trigger habitat selection by animals may be decoupled from the resources linked evolutionarily to that cue, creating the potential for an ecological trap. Plant invasions also influence the ecological drivers that maintain grasslands in an open condition, which will alter the long‐term dynamics of plant and animal populations. Specifically, by increasing fuel load and continuity, fires in invaded grasslands increase in frequency and intensity relative to those in native grasslands. Although eradication is unlikely once a non‐native plant has naturalized, retaining patches of native vegetation within a matrix of non‐native plants may provide a strategy to reduce effects of plant invasions on wildlife in grasslands. © 2013 The Wildlife Society.

Mechanisms of the impact of a weed (grader grass, Themeda quadrivalvis ) on reptile assemblage structure in a tropical savannah

“…Hacking et al (2014) reached a similar conclusion for this habitat for a single skink species. The dense growth form of grader grass may increase the costs of locomotion (Newbold, 2005), make social interactions more difficult (Steidl et al, 2013), and reduce reproductive success (Martin and Murray, 2011). Opportunities for thermoregulation are also likely to be reduced in grader grass (Valentine et al, 2007;Hacking et al, 2014).…”

“…Non-native grasses reduce the extent of native grass (Hacking et al, 2014), and sites that are dominated by grass swards (or bare ground), tended to have lower reptile species richness and lower abundances than habitats with hummock grasses, which create a more diverse vegetation structure (Garden et al, 2007;Foxcroft et al, 2010;Price et al, 2010;Kutt and Fisher, 2011;Kutt and Kemp, 2012). Dense, uniform grass cover may affect the mobility of reptiles, reducing their ability to forage, escape predators, and engage in social interactions (Steidl et al, 2013). Reptiles clearly had preferences for specific grass types.…”

“…Similarly, semi-arboreal fence skinks (C. adamsi) were not detected in grader grass, possibly due to lack of structural features. In general, complex habitat structure may be preferred by arboreal reptiles, and others requiring more diverse habitat features for foraging, perching, basking, and refuge (Garden et al, 2007;Mott et al, 2010;Pike et al, 2011;Steidl et al, 2013).…”

“…The influence of weeds on reptile assemblage composition and abundance may be driven by a variety of factors. Food availability may be altered in weeds (Valentine, 2006;Martin and Murray, 2011), predators may be more abundant or more successful in weeds (e.g., Thompson, 1987), habitat structure of weeds may alter behaviour, such as movement and social interactions (Newbold, 2005;Downes and Hoefer, 2007;Rieder et al, 2010;Steidl et al, 2013), or influence thermoregulation (Valentine, 2006;Downes and Hoefer, 2007). Studies examining the likely sources of the impacts of weeds are required to predict the effects of weeds in different habitats and on other faunal assemblages (Martin and Murray, 2011).…”

Plant invasions alter settlement patterns of breeding grassland birds

“…This unusually long period between territory establishment and reproduction makes the link between proximate cues used to select habitat and future resources especially important (Włodarczyk and Minias 2016). Because the proximate cues animals use to select habitat are often related to plant structure, settlement responses to invasions may be conditional on structural similarities between nonnative and native plants and the habitat preferences of the species selecting habitat (Steidl et al 2013). Although these two sparrows are similar ecologically and both are classified as grassland obligates (Vickery et al 1999), they differ in their habitat preferences and breadth (i.e., the width of the habitat component of a species' niche).…”