Plant invasion in deserts: From plant traits to community invasibility

ANDRÉS G. ROLHAUSER; M. GABRIEL GATICA; MARTÍN AGUIAR; EDUARDO PUCHETA

Mar del Plata

Conferencia; Biolief 2011. 2nd World Conference on Biological Invasions and Ecosystem Functioning; 2011

Grupo de Investigación y Educación en Temas Ambientales (GrIETA)

Community assembly theory appears as a potentially valuable tool to understand community invasibility. Classic trait-based community theory predicts that invasion would be unlikely if the invader´s traits overlap with those of the resident species. More recently, however, it has been proposed that invasion would not only result from niche differences between invader and resident species, but also from a fitness advantage, and that only the latter allows invaders to outcompete residents and become dominant. Here we confront these ideas by looking into the relationship between functional traits of annual plant species and their distribution and abundance in the field over one growing season (2010-2011). Our study case was a summer-rainfall, shrub-dominated desert in San Juan, Argentina, where both native and exotic annual plant species coexist. A trait-based principal component analysis (including specific leaf area, leaf dry matter content, specific root length, and specific root diameter) showed that 4 out of 5 exotic species were functionally similar to the natives (26 species). Moreover, 3 of those 4 exotic species were among the most abundant species, including Tribulus terrestris (Zygophyllaceae), which was the dominant species in the understory during summer. We suggest that the success of these abundant and potentially harmful invaders could be related to fitness advantages but not to niche differences. Our results support the recent view that fitness differences between native and invasive species (and not only niche or trait differences) need to be considered for a comprehensive understanding of biological invasions.