Disturbance by an endemic rodent in an arid shrubland is a habitat filter: effects on plant invasion and taxonomical, functional and phylogenetic community structure

Abstract

Background and Aims Disturbance often drives plant invasion and may modify community assembly. However, little is known about how these modifications of community patterns occur in terms of taxonomic, functional and phylogenetic structure. This study evaluated in an arid shrubland the influence of disturbance by an endemic rodent on community functional divergence and phylogenetic structure as well as on plant invasion. It was expected that disturbance would operate as a habitat filter favouring exotic species with short life cycles.Methods Sixteen plots were sampled along a disturbance gradient caused by the endemic fossorial rodent Spalacopus cyanus, measuring community parameters and estimating functional divergence for life history traits (functional dispersion index) and the relative contribution to functional divergence of exotic and native species. The phylogenetic signal (Pagel's lambda) and phylogenetic community structure (mean phylogenetic distance and mean nearest taxon phylogenetic distance) were also estimated. The use of a continuous approach to the disturbance gradient allowed the identification of non-linear relationships between disturbance and community parameters.Key Results The relationship between disturbance and both species richness and abundance was positive for exotic species and negative for native species. Disturbance modified community composition, and exotic species were associated with more disturbed sites. Disturbance increased trait convergence, which resulted in phylogenetic clustering because traits showed a significant phylogenetic signal. The relative contribution of exotic species to functional divergence increased, while that of natives decreased, with disturbance. Exotic and native species were not phylogenetically distinct.Conclusions Disturbance by rodents in this arid shrubland constitutes a habitat filter over phylogeny-dependent life history traits, leading to phylogenetic clustering, and drives invasion by favouring species with short life cycles. Results can be explained by high phenotypic and phylogenetic resemblance between exotic and native species. The use of continuous gradients when studying the effects of disturbance on community assembly is advocated.

Goat grazing reduces diversity and leads to functional, taxonomic, and phylogenetic homogenization in an arid shrubland

“…For taxonomic contribution, we used the percentage of abundance (cAbundance) and richness (cRichness) of exotic species per plot. For functional contribution, we used the relative contribution of exotic species to FDis (cFDis) following Escobedo et al (). For phylogenetic contribution, we used the contribution of exotic species to Phylogenetic Species Evenness (Helmus, Bland, Williams, & Ives, ) per plot.…”

“…By excluding species from the community, grazing can alter the functional and phylogenetic structure and diversity of the community (de Bello et al, ; Escobedo, Rios, Salgado‐Luarte, Stotz, & Gianoli, ), which are important indicators of ecosystem function and services (Altesor, Oesterheld, Leoni, Lezama, & Rodríguez, ; Leoni, Altesor, & Paruelo, ; Piñeiro, Paruelo, Oesterheld, & Jobbágy, ). Grazing can act as a ‘habitat filter’ (de Bello et al, ; Laliberté, Norton, & Scott, ), where only species with particular traits or strategies are able to establish and persist in the community (Kraft et al, ).…”

Interactive effects of shading and disturbance on plant invasion in an arid shrubland: Assembly processes and CSR‐strategies

“…Soil disturbance by fossorial mammals can have opposite effects on assembly and invasion processes depending on whether microsites have low or ample resource availability (El‐Bana, 2009; Escobedo et al., 2017; Mallen‐Cooper et al., 2019; Root‐Bernstein & Ebensperger, 2013; Wesche et al., 2007). In resource‐poor environments, as open areas in arid ecosystems, both native and exotic populations usually fail to recover from disturbance, which increases environmental stress (Huston, 1994, 2004).…”

“…The ecological effects of disturbance by S . cyanus are mainly mediated by physical phenomena (plant removal/burial) rather than by increased soil nutrient availability, plant consumption or enhanced microclimatic conditions (Contreras et al., 1993; Escobedo et al., 2017). In turn, F. thurifera may function as a nurse plant, facilitating the establishment of plant species by ameliorating microclimatic conditions and increasing soil nutrient availability due to the joint effects of shading and hydraulic lift (Cares et al., 2013; León & Squeo, 2004).…”

“…Specifically, this was done in four microsites resulting from the factorial combination of disturbance (undisturbed vs. disturbed by the fossorial rodent Spalacopus cyanus-Octodontidae) and shading (in open areas vs. beneath the canopy of the dominant shrub Flourensia thurifera-Asteraceae). The ecological effects of disturbance by S. cyanus are mainly mediated by physical phenomena (plant removal/burial) rather than by increased soil nutrient availability, plant consumption or enhanced microclimatic conditions (Contreras et al, 1993;Escobedo et al, 2017). In turn, F. thurifera may function as a nurse plant, facilitating the establishment of plant species by ameliorating microclimatic conditions and increasing soil nutrient availability due to the joint effects of shading and hydraulic lift (Cares et al, 2013;León & Squeo, 2004).…”