Species distributional or trait data based on range map (extent-of-occurrence) or atlas survey data often display spatial autocorrelation, i.e. locations close to each other exhibit more similar values than those further apart. If this pattern remains present in the residuals of a statistical model based on such data, one of the key assumptions of standard statistical analyses, that residuals are independent and identically distributed (i.i.d), is violated. The violation of the assumption of i.i.d. residuals may bias parameter estimates and can increase type I error rates (falsely rejecting the null hypothesis of no effect). While this is increasingly recognised by researchers analysing species distribution data, there is, to our knowledge, no comprehensive overview of the many available spatial statistical methods to take spatial autocorrelation into account in tests of statistical significance. Here, we describe six different statistical approaches to infer correlates of species' distributions, for both presence/absence (binary response) and species abundance data (poisson or normally distributed response), while accounting for spatial autocorrelation in model residuals: autocovariate regression; spatial eigenvector mapping; generalised least squares; (conditional and simultaneous) autoregressive models and generalised estimating equations. A comprehensive comparison of the relative merits of these methods is beyond the scope of this paper. To demonstrate each method's implementation, however, we undertook preliminary tests based on simulated data. These preliminary tests verified that most of the spatial modeling techniques we examined showed good type I error control and precise parameter estimates, at least when confronted with simplistic simulated data containing

Many animals are regarded as relatively sedentary and specialized in marginal parts of their geographical distributions. They are expected to be slow at colonizing new habitats. Despite this, the cool margins of many species' distributions have expanded rapidly in association with recent climate warming. We examined four insect species that have expanded their geographical ranges in Britain over the past 20 years. Here we report that two butterfly species have increased the variety of habitat types that they can colonize, and that two bush cricket species show increased fractions of longer-winged (dispersive) individuals in recently founded populations. Both ecological and evolutionary processes are probably responsible for these changes. Increased habitat breadth and dispersal tendencies have resulted in about 3- to 15-fold increases in expansion rates, allowing these insects to cross habitat disjunctions that would have represented major or complete barriers to dispersal before the expansions started. The emergence of dispersive phenotypes will increase the speed at which species invade new environments, and probably underlies the responses of many species to both past and future climate change.

The first expected symptoms of a climate change-generated biodiversity crisis are range contractions and extinctions at lower elevational and latitudinal limits to species distributions. However, whilst range expansions at high elevations and latitudes have been widely documented, there has been surprisingly little evidence for contractions at warm margins. We show that lower elevational limits for 16 butterfly species in central Spain have risen on average by 212 m (± SE 60) in 30 years, accompanying a 1.3 °C rise (equivalent to c. 225 m) in mean annual temperature. These elevational shifts signify an average reduction in habitable area by one-third, with losses of 50-80% projected for the coming century, given maintenance of the species thermal associations. The results suggest that many species have already suffered climate-mediated habitat losses that may threaten their long-term chances of survival.

The geographic ranges of many species have shifted polewards and uphill in elevation associated with climate warming, leading to increases in species richness at high latitudes and elevations. However, few studies have addressed community-level responses to climate change across the entire elevational gradients of mountain ranges, or at warm lower latitudes where ecological diversity is expected to decline. Here, we show uphill shifts in butterfly species richness and composition in the Sierra de Guadarrama (central Spain) between 1967-1973 and 2004-2005. Butterfly communities with comparable species compositions shifted uphill by 293 m (AE SE 26), consistent with an upward shift of approximately 225 m in mean annual isotherms. Species richness had a humped relationship with elevation, but declined between surveys, particularly at low elevations. Changes to species richness and composition primarily reflect the loss from lower elevations of species whose regional distributions are restricted to the mountains. The few colonizations by specialist low-elevation species failed to compensate for the loss of high-elevation species, because there are few low-elevation species in the region and the habitat requirements of some of these prevent them from colonizing the mountain range. As a result, we estimated a net decline in species richness in approximately 90% of the region, and increasing community domination by widespread species. The results suggest that climate warming, combined with habitat loss and other drivers of biological change, could lead to significant losses in ecological diversity in mountains and other regions where species encounter their lower latitudinal-range margins.