Floristic patterns and plant traits of Mediterranean communities in fragmented habitats

Abstract

Unveiling the processes that determine the spatial distribution of species is a central goal for community ecology and biogeography. Hubbell (1997Hubbell ( , 2001 suggested that the dispersal history of biological assemblages, rather than habitat specialization, provides the main explanation for spatial variation. Neutral theory predicts that among-site floristic similarity (beta-diversity or commonality) should decrease logarithmically with increasing geographical distance because ABSTRACT Aim To contrast floristic spatial patterns and the importance of habitat fragmentation in two plant communities (grassland and scrubland) in the context of ecological succession. We ask whether plant assemblages are affected by habitat fragmentation and, if so, at what spatial scale? Does the relative importance of the niche differentiation and dispersal-limitation mechanisms change throughout secondary succession? Is the dispersal-limitation mechanism related to plant functional traits?Location A Mediterranean region, the massif of Albera (Spain).Methods Using a SPOT satellite image to describe the landscape, we tested the effect of habitat fragmentation on species composition, determining the spatial scale of the assemblage response. We then assessed the relative importance of dispersal-related factors (habitat fragmentation and geographical distance) and environmental constraints (climate-related variables) influencing species similarity. We tested the association between dispersal-related factors and plant traits (dispersal mode and life form). ResultsIn both community types, plant composition was partially affected by the surrounding vegetation. In scrublands, animal-dispersed and woody plants were abundant in landscapes dominated by closed forests, whereas winddispersed annual herbs were poorly represented in those landscapes. Scrubby assemblages were more dependent on geographical distance, habitat fragmentation and climate conditions (temperature, rainfall and solar radiation); grasslands were described only by habitat fragmentation and rainfall. Plant traits did not explain variation in spatial structuring of assemblages.Main conclusions Plant establishment in early Mediterranean communities may be driven primarily by migration from neighbouring established communities, whereas the importance of habitat specialization and community drift increases over time. Plant life forms and dispersal modes did not explain the spatial variation of species distribution, but species richness within the community with differing plant traits was affected by habitat patchiness.

Composition and diversity of herbaceous patches in woody vegetation: The effects of grazing, soil seed bank, patch spatial properties and scale

“…As oppose to our hypothesis (H2B) and to studies that found geographical distance a major determinant of beta diversity at large-scale (Chust et al, 2006), we found no relation between beta diversity and the average distance between patches at the small scale. Probably at our scale the size and the accessibility of the patches plays more important role than the absolute distance between patches.…”

Forest vegetation responses to climate and environmental change: A case study from Changbai Mountain, NE China

“…Initially, fragmentation and isolation of habitats might protect their species from being out-competed by species better adapted to increases in temperature and precipitation changes (Kissling et al, 2008). Nonetheless, it can be expected that the fitness of many species will eventually decrease, leading to changes in the composition of the vegetation and to a decrease in local species diversity (Chust et al, 2006).…”

Mapping and quantifying habitat fragmentation in small coastal areas: a case study of three protected wetlands in Apulia (Italy)

“…This is causing a dramatic reduction in biodiversity (Brooks et al 2002;Fahring 2002Fahring , 2003Hoffmeister et al 2005) and strong alteration in plant richness and composition (Bascompte and Rodríguez 2001;Chust et al 2006).…”