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...terature. Yet, still, the fundamental question of why species are distributed as they are remained a scientific puzzle (Rosen 1988, Webb and Bartlein 1992, Hoffmann and Blows 1994, Brown et al. 1996, =-=Gaston 2000-=-). In the last 10 years, events outside of science have sparked a revival of interest in this question, not only among scientists but also in the public and governmental sectors. Global warming, exoti...

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...ex (NCI) concept (Ten Brink, 2000). Alkemade et al. (in preparation)4 assessed the impact of different land uses on the relative species abundance, the ecosystem quality, for the GLOBIO3 modelling development. Agro-ecosystem quality is the result of combined effects of several pressures on the landscape scale of analysis. We focus on the impact of land-use intensity, which includes the combined effects of ploughing frequency, fertilizer and pesticide applications, and specialization of production, monoculture, and crop or grass productivity. Tilman et al. (2001), Zechmaister and Moser (2001), Gaston (2000) and Wilson et al. (2003) showed a strong correlation between land-use intensity and biodiversity loss. A literature review was carried out on the following to determine the dose-effect relationship of the intensity of agricultural land use on biodiversity: l3 4 and-use–biodiversity loss gradients (comparison between land-use systems and the pristine, or low human impact, situation); pair-wise comparison of biodiversity impact between different farm types (separate for cropping and grassland systems);http://www.eu2004.ie/templates/document_file.asp?id=17810. Contact the corresponding author ...

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... variability of species richness across different regions. While some regions harbor a high proportion of biological diversity, others are almost devoid of species, and most lie somewhere in between (=-=Gaston 2000-=-). The gradient of species richness, from low at the poles to high at equatorial regions, is probably the most widely recognized pattern of species diversity. Despite the long history of the so-called...

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...he number of species in an area and the availability of environmental energy is fundamental to an understanding of spatial variation in species richness (Wright 1983; Turner et al. 1988; Currie 1991; =-=Gaston 2000-=-; Kaspari et al. 2000; Hurlbert & Haskell 2003). Studies so far have primarily concerned the establishment of the form and occurrence of species–energy relationships. These have variously been found t...

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... in central Europe represent a mix of speciation and immigration from other regions, with both processes operating over tens of millions of years, it may be historic (or non-European) habitats rather than current European habitat areas that are relevant, clouding the interpretation of any correlation between habitat area and species richness. In addition, historical disturbance, notably glaciations and associated drier periods, may have a significant effect on the extinction of European species and therefore the composition of the current regional species pool (Grubb 1987, Taylor et al. 1990, Gaston 2000). Current theory posits that high biomass leads to competition for light, which then causes the humpshaped richness–productivity relationship (Grime 1979). Clearly there are different classes of controls on OIKOS 100:3 (2003) 421 Table 2. Published studies that found a significant relationship between a proxy for productivity and plant species richness. Unless noted all studies counted species richness of all vascular plants. Peak species richness was calculated using the regression equation or directly from the data presented in each study. A significant quadratic term was used to identify hu...

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...h canopy closure as the second predictor. Despite suitable local quality of the woodland key habitats, the density of such habitat patches may in many areas be too low for long-term protection of saproxylic beetles associated with broadleaved temperate forests. Landscapes with many clustered woodland key habitats rich in oak should have high priority for conservation of saproxylic oak beetles. 2006 Elsevier Ltd. All rights reserved.1. Introduction In biogeography, species richness and composition are clearly related to latitude and altitude (Wright, 1983; Stevens, 1989; Cox and Moore, 1999; Gaston, 2000). Species richness and composition are also assumed to depend on spatio-temporal factors such as region, landscape quality and configuration, habitat continuity, and habitat or stand quality (Meffe and Carroll, 1997; Nilsson and Baranowski, 1997; Forman, 1999; Gaston and Blackburn, 2000). Some studies emphasize the importance of the surrounding landscape for local specieser Ltd. All rights reserved ; fax: +46 31 41 67 29. (N. Franc), frank.gotmar orden), heidi.paltto@botrichness. For instance, the surrounding landscape seems to influence species richness of birds in riparian forests (Saab, 19...

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...ales relaciones pueden cambiar rapidamente a lo largo de gradientes ambientales. INTRODUCTION It is well known that animal species and higher taxa such as families are not evenly distributed throughout the Earth, and that their diversity often changes along environmental gradients. For example, most groups of insects such as ants, termites, butterflies and beetles are most species-rich at low latitudes. Relatively few insect groups, e.g. aphids, sawflies, syrphids, psyllids, ichneumonids, braconids and bees, reach their highest species numbers at higher latitudes (Gauld, 1987; Holloway, 1987; Gaston 2000 and references therein; but see Horstmann et al., 1999). There is an intense debate about the possible underlying mechanisms of latitudinal patterns of species richness (Chown & Gaston, 2000). However, altitudinal gradients have often been neglected despite their potential as powerful natural experimental systems (K€orner, 2000; Lomolino, 2001). Altitudinal gradients offer very different climates and habitat types in close proximity to each other. The role of historical factors such as long-lasting isolation is much less pronounced than in latitudinal gradients, and at least for more mobile o...

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... posits that the latitudinal gradient in species richness is primarily a function of energy availability, with species richness of a region positively related to solar energy input (Wright 1983; Wright et al. 1993; Fraser and Currie 1996; Kerr and Packer 1997). Thus, a positive correlation between some measure of energy and species richness is generally taken as supporting this hypothesis (Fraser and Currie 1996; Kerr and Packer 1997; Roy, Jablonski, and Martien 2000; Francis and Currie 2003). However, the actual mechanisms relating available energy to species richness remain largely unknown (Gaston 2000), so that specific predictions regardine, for example, the slope of the speaes-energy relationship have been lacking. Energy can be regarded either as an element in trophic dynamics, in which case it is related to the regime of productivity that includes solar radiation and nutrient supply (Valentine 19831, or as generating diversity patterns through metabolic scaling relationships, in which case it is related to emp e r a m per se (Alien et al. 2002). While a positive relationship between energy and species richness is known in groups ranging from terrestrial trees and mammals to marine mollu...