Predictability of plant species composition from environmental conditions is constrained by dispersal limitation

Abstract

2005. Predictability of plant species composition from environmental conditions is constrained by dispersal limitation. Á/ Oikos 108: 555 Á/561.Despite recent modelling approaches integrating the effects of niche-based processes and dispersal-based processes on local plant species composition, their relative importance is still not clear. We test whether the predictability of local species composition from environmental conditions is influenced by dispersal traits. We analyzed a large database with co-occurrence data, using ordination techniques (DCA and CCA) to identify the major environmental determinants of species composition. The percentage of explained variance in occurrence was quantified for individual species with CCA. Effects of life-history traits on the predictability of occurrence patterns were tested by means of regression analysis, using a generalized linear models approach. The results reveal close correlations between species composition and environmental conditions, implying that the predictability of the set of species that might occur in a given environmental setting (''habitat species pool'') is high. The habitat species pool, however, reflects the potential species composition, and not the actual local situation. At the level of individual species, a large proportion ( /90%) of the variation in occurrence remained unexplained. Predictability of species occurrence patterns was increased by a greater capacity for long-distance dispersal, greater adult longevity and the capacity to build a persistent seed bank. The results indicate that the predictability of species composition from environmental conditions is reduced by a few orders of magnitude by dispersal limitation and that poor dispersers are underrepresented.Understanding plant species diversity requires insight into the mechanisms that determine species richness, but also into the mechanisms that determine local species composition. Compared to species richness, species composition is more difficult to assess, as this requires a more detailed knowledge of the constituent species. Species composition involves not only the number of species and the abundance of each species, but also the specific nature of the species. Local species composition arises partly from stochastic processes such as local extinctions due to demographic drift and rare long distance dispersal events, and partly from deterministic processes linking habitat characteristics to speciesspecific niches.

Local randomness, vegetation type and dispersal drive bird and mammal's diversity in a tropical South American region

“…;Lomolino 1990) and lower extinction rates (MacArthur and Wilson 1967). At local scales, niche processes are more likely to influence species distribution than neutral processes because, at local scales, species compete (Silvertown et al 1999) and can reach all areas where they are able to survive (Ozinga et al 2005). It is also in this scale that local random extinctions are more likely to occur due to the reduced number of individuals in local populations.…”

Advances, challenges and a developing synthesis of ecological community assembly theory

“…(iv) Dispersal limits are small relative to the effects of the abiotic and biotic filters in determining functional community composition. That is, species composition may be largely dispersal limited [37,38], but functional composition is much less so [39]. In addition, traits associated with dispersal ability can be incorporated to assess the degree of dispersal limitation [37,40].…”

“…This is because different subsets of the regional pool can be selected by their traits while historical dispersal and drift determine the actual species composition. This is one reason why it is not surprising that species composition is usually not particularly predictable [37], and why ecologists are sceptical when it is predictable [41 -43]. There is no real assumption of equilibrium, but rather on-going, iterative filtering and sorting processes constrain community assembly and make some assemblages less likely to persist than others [44][45][46].…”

Rook Spring Seed Dispersal in the Agricultural Landscape – Frugivory, Granivory or Accidental Transport?

“…Dispersal limitation is often crucial for local species composition and vegetation structure (Eriksson and Ehrlén 1992;Wang and Smith 2002;Ozinga et al 2005). Plant movement is limited to the dispersal of seeds and pollen and it is usually mediated by animal agents, wind, water, gravity or caused by intrinsic explosive mechanisms (Wang and Smith 2002;Jordano et al 2011).…”