Environment, dispersal and patterns of species similarity

Abstract

Explaining patterns of spatial variation in species composition is a major challenge facing ecologists. While many studies have focused on patterns of species richness and their causal factors, the spatial change in species composition has received far less attention (but see Harrison et al. ABSTRACTAim The aim of this paper is to evaluate the combined effects of geographical distance and environmental distance on patterns of species similarity (similarity in species composition between sites), and to identify factors affecting the rate of decay in species similarity with each type of distance.Location Israel.Methods Data on species composition of land snails and land birds were recorded in 27 sites of 1 · 1 km scattered across a rainfall gradient in Israel. Matrices of similarity in species composition between all pairs of sites were computed and analysed with respect to corresponding matrices of geographical distance and rainfall distance (defined as the difference in mean annual rainfall between sites, and used as a measure of environmental distance). Mantel tests were applied to determine the correlation between species similarity and each type of distance. Factors affecting the decay in species similarity were investigated by comparing different subsets of the data using randomization tests.Results Both rainfall distance and geographical distance had negative effects on species similarity. The effect of rainfall distance was statistically significant even after controlling for differences in geographical distance, and vice versa. The perunit effect of rainfall distance on species similarity decreased with increasing geographical distance, indicating that the two types of distances interacted in determining the similarity in species composition. Snails showed a higher rate of decay in species similarity with geographical distance than birds, and large snails showed a higher rate of decay than small snails, which are better passive dispersers. The per-unit effects of both rainfall distance and geographical distance on species similarity were higher in the desert region than in the Mediterranean region. Analyses focusing on a grain size of 10 · 10 m showed a lower similarity in species composition and a lower rate of decay in species similarity with rainfall distance than analyses carried out at a grain size of 1 · 1 km.Main conclusions Patterns of similarity in species composition are influenced by the combined effects of environmental variation, the position of the area along environmental gradients, the dispersal properties of the component species, and the scale (both spatial extent and grain size) at which the patterns are examined.

Taxonomic groups with lower movement capacity may present higher beta diversity

“…Accordingly, several studies have demonstrated a host of different factors that may influence variation of species composition through space: (1) spatial and environmental gradients (e.g. Clark et al, 1999;Nekola & White, 1999;Oliveira-Filho & Fontes, 2000;Carneiro & Valeriano, 2003;Steinitz et al, 2006Steinitz et al, , 2007bLegendre et al, 2009); (2) differences in the physiology, in the degree of biological interactions and in the dispersal ability of the species (Nekola & White, 1999;Tuomisto et al, 2003;Gilbert & Lechowicz, 2004); (3) barriers imposed by the configuration of the landscape and the influence of weather on species' dispersion (Nekola & White, 1999;Hubbel, 2001); (4) stochastic processes generated randomly and independently of environmental dissimilarities (Neutral Theory sensu Hubbel, 2001;Soininen et al, 2007b;Steinbauer et al, 2012); (5) species' tolerance to fragmentation (Arroyo-Rodríguez et al, 2013); (6) spatial scale (extension, resolution; Nekola & White, 1999;Steinitz et al, 2006;Soininen et al, 2007b;Arroyo-Rodríguez et al, 2013). Therefore, more accurate analysis involving other variables could yield further explanations regarding the spatial distribution observed in this study.…”

“…Such relation is partially due to the spatial autocorrelation pattern of environmental variables, with closer locations tending to be more environmentally similar to each other (Legendre, 1993), which, by itself, influences the composition of species communities (Harrison et al, 1992;Jiménez-Valverde et al, 2010). Therefore, a decrease in the similarity of environmental conditions along space may result in a correspondent decrease of the similarity in species composition (Steinitz et al, 2006).…”

“…Such relation is partially due to the spatial autocorrelation pattern of environmental variables, with closer locations tending to be more environmentally similar to each other (Legendre, 1993), which, by itself, influences the composition of species communities (Harrison et al, 1992;Jiménez-Valverde et al, 2010). Therefore, a decrease in the similarity of environmental conditions along space may result in a correspondent decrease of the similarity in species composition (Steinitz et al, 2006).Among the biotic factors that may influence the pattern of beta diversity there are the life history of the species (Soininen et al, 2007a) and the organisms' dispersal ability (Dobrovolski et al, 2011). Also, taxonomic groups of organisms may be broadly categorized in a gradient according to their dispersal abilities.…”

Spatial Patterns of Phytodiversity - Assessing Vegetation Using (Dis) Similarity Measures

“…For multivariate data Mantel correlograms can be applied (Legendre & Legendre 1998;Sokal & Rohlf 1981). A simple possibility for vegetation data is to regress similarity of units regarding species composition against their geographical separation (Nekola and White, 1999;Steinitz et al, 2006). To test for the influence of different vegetation types on patterns of compositional similarity data was divided into subsets.…”

“…Here, we investigate the distance decay of compositional similarity whilst accounting for the change of the relationship between compositional similarity and its drivers with geographical distance between plots. Steinitz et al, (2006) highlight that the studies are limited to which extent patterns of distance decay depend on the position along environmental gradients. Accordingly Jones et al, (2006) emphasize that explanatory power of variables might increase with the length of the gradient covered.…”