Resistance to Centaurea solstitialis invasion from annual and perennial grasses in California and Argentina

Abstract

A common explanation for Centaurea solstitialis invasion in California is that it occupies an ''empty niche'' created by the replacement of native perennial grasses by exotic annual grasses and concomitant increases in soil water availability. This hypothesis, however, cannot explain C. solstitialis invasion into perennial-dominated grasslands of central Argentina. We assessed invasibility of annual versus perennial grass communities in these regions through parallel field experiments where we created grass plots and, after one year of establishment, measured effects on water and light, and added C. solstitialis seeds in two successive trials. Additionally, we removed vegetation around naturally occurring C. solstitialis in both regions, and examined the performance of Californian and Argentinean C. solstitialis individuals when growing under common conditions simulating climate in California and Argentina. In California, both grass types offered high resistance to C. solstitialis invasion, water was generally greater under perennials than annuals, and light was similarly low beneath both types. In Argentina, invasibility was generally greater in annual than perennial plots, water was similar between groups, and light was much greater beneath annuals. Removal experiments showed that competition from annual grasses in California and perennial grasses in Argentina greatly reduce C. solstitialis performance. Additionally, Californian and Argentinean individuals did not exhibit genetic differentiation in studied traits. Our results suggest that dominant plant functional groups in both California and Argentina offer substantial resistance to C. solstitialis invasion. The success of this species might be tightly linked to a remarkable ability to take advantage of disturbance in both regions.

Fire and simulated herbivory have antagonistic effects on resistance of savanna grasslands to alien shrub invasion

“…Previous studies have shown that invasibility of grassland communities, i.e. the susceptibility to being invaded, increases with disturbance (Hobbs 1989;Cano et al 2007;Hierro et al 2011). In the current study, we show a similar result.…”

“…Here, we present the results of a study designed to investigate how disturbance regimes can modify biotic resistance. Disturbance commonly promotes invasion success by temporarily reducing competition and, hence, biotic resistance of communities, thereby increasing their susceptibility to invasion (Hobbs & Huenneke 1992;Hierro et al 2006Hierro et al , 2011Cano et al 2007). The effects of disturbance are scale-dependent and can have long-lasting effects beyond the disturbance event itself.…”

Biotic resistance affects growth and reproduction, but not survival of a high‐impact woody invader in African savannas

“…Biotic resistance from the native community is a key factor controlling invasion success via competition, herbivory and/or pathogens (Elton, 1958;Levine, Adler, & Yelenik, 2004). Many studies on biotic resistance focus on the effect of competition during the early life stages (Cano, Escarre, & Sans, 2007;Eskelinen & Harrison, 2014;Hierro, Lortie, Villarreal, Estanga-Mollica, & Callaway, 2011;te Beest, Mpandza, & Olff, 2015;Thomsen, Corbin, & D'Antonio, 2006;Thomsen & D'Antonio, 2007). However, to what extent competition from resident communities affects survival and persistence during later life stages of long-lived woody plants is much less known.…”

Native and non-native ruderals experience similar plant–soil feedbacks and neighbor effects in a system where they coexist

“…We performed the study in the semiarid open forest of caldén (Prosopis caldenia, Fabaceae) in central Argentina, commonly known as the Caldenal (Cano et al 1980;Cabrera 1994). Similar to many natural systems around the world, most non-native invasive plants in the Caldenal are ruderals (sensu Grime 1974;Baker 1974;Mack et al 2000;Hierro et al 2005Hierro et al , 2006Hierro et al , 2011Pearson et al 2014a). Consequently, and in order to contrast native and non-native species with similar life-history strategies, we focused on comparing native vs. non-native ruderals.…”