How does habitat diversity affect the species–area relationship?

Abstract

Aim To examine the way in which ‘area’ and ‘habitat diversity’ interact in shaping species richness and to find a simple and valid way to express this interaction. Location The Natura 2000 network of terrestrial protected areas in Greece, covering approximately 16% of the national territory. Methods We used the Natura 2000 framework, which provides a classification scheme for natural habitat types, to quantify habitat heterogeneity. We analysed data for the plant species composition in 16,143 quadrats in which 5044 species and subspecies of higher plants were recorded. We built a simple mathematical model that incorporates the effect of habitat diversity on the species–area relationship (SAR). Results Our analysis showed that habitat diversity was correlated with area. However, keeping habitat diversity constant, species richness was related to area; while keeping area constant, species richness was related to habitat diversity. Comparing the SAR of the 237 sites we found that the slope of the species–area curve was related to habitat diversity. Main conclusions Discussion of the causes of the SAR has often focused on the primacy of area per se versus habitat heterogeneity, even though the two mechanisms are not mutually exclusive and should be considered jointly. We find that increasing habitat diversity affects the SAR in different ways, but the dominant effect is to increase the slope of the SAR. While a full model fit typically includes a variety of terms involving both area and habitat richness, we find that the effect of habitat diversity can be reduced to a linear perturbation of the slope of the species accumulation curve.

Turnover of soil bacterial diversity driven by wide-scale environmental heterogeneity

“…5), thereby supporting the environmental selection hypothesis for soil microorganisms 3,7 . It is interesting to note that z bacteria values may attain those reported for larger organisms (ca.…”

“…Our study negates the hypothesis that the soil microbial community is a ''black box'' with no spatial structure and exhibiting a homogeneous distribution from local to large scales. As observed in macroorganisms, spatial patterns in soil bacterial communities are also significantly governed by environmental heterogeneity and dispersal, and the two processes are not mutually exclusive 2,7 . Moreover, the environmental filters impacting the turnover of soil microbial diversity as a whole need to be deciphered and ranked to better understand the sustainability of the soil ecosystem services provided by the corresponding biodiversity.…”

“…Application of the TAR has demonstrated that the species richness of eukaryotic macroorganisms increases with the sampling area 7 . This significant rate of diversity turnover has generally been explained by a dynamic equilibrium between extinction and immigration (''area'' hypothesis, mediated by dispersal) and/or by the increase of habitat diversity with increasing area (''habitat heterogeneity'' hypothesis, mediated by environmental selection) 7 .…”

“…Application of the TAR has demonstrated that the species richness of eukaryotic macroorganisms increases with the sampling area 7 . This significant rate of diversity turnover has generally been explained by a dynamic equilibrium between extinction and immigration (''area'' hypothesis, mediated by dispersal) and/or by the increase of habitat diversity with increasing area (''habitat heterogeneity'' hypothesis, mediated by environmental selection) 7 . In microorganisms, phylogeographic studies have revealed that the genetic similarity within particular populations decreases with distance, which suggests a significant influence of dispersal limitation, leading to strong endemism 3 , and contradicts the hypothesis of microbial cosmopolitanism 8 .…”

Uncertainties in the application of the species area relationship for characterisation factors of land occupation in life cycle assessment

“…Koellner and Scholz (2008) and Schmidt (2008) use a constant z value of 0.21 or 0.23 to calculate CFs for land use. However, the value of the species accumulation factor z is widely discussed (Rosenzweig 1995;Crawley and Harral 2001;Collins et al 2002) and depends on the type of habitat (Hannus and von Numers 2008;Kallimanis et al 2008), the taxa (Humphreys and Kitchener 1982;Collins et al 2002), and the size of the area (Lomolino 2001;Crawley and Harral 2001;Losos and Schluter 2000;Kallimanis et al 2008;Harner and Harper 1976). A range of land use type and spatial scale specific z values are published (Crawley and Harral 2001;Manhoudt et al 2005;Dolnik and Breuer 2008).…”