Latitudinal and Elevational Range Shifts under Contemporary Climate Change range shifts by comparing historical and modern data on a species’ distribution across its entire ranges or sections of the range; and (2) studies that infer range shifts by comparing historical and modern data on species composition or abundance within local communities The following sections cover both types of studies Latitudinal Range Shifts We carried out a selective review of historically based studies documenting contemporary latitudinal range shifts Many species across many organism groups ranging from the most simple such as plankton, algae, and lichens to the most complex such as flowering plants, birds, and mammals, across both marine and terrestrial ecosystems, have shifted their latitudinal ranges over recent decades (Table 1) Most of these contemporary latitudinal range shifts are coherent with contemporary climate change, even though some studies reported the absence of latitudinal range shifts or even unexpected latitudinal range shifts, in addition to the expected and empirically predominant poleward range shifts (Thomas and Lennon, 1999; Warren et al., 2001; Hill et al., 2002; Brommer, 2004; Hitch and Leberg, 2007; La Sorte and Thompson, 2007) Most latitudinal range shifts have been documented within the animal kingdom (invertebrates, fishes, amphibians, reptiles, birds, and mammals), whereas only a handful of cases have so far been documented for plants (Table 1) Among animals, there is clear evidence of poleward range shifts through either expansion at the leading edge or retraction at the trailing edge (Parmesan et al., 1999; Hickling et al., 2005), or increasing and decreasing abundance at the front and rear edges, respectively (Sagarin et al., 1999; Myers et al., 2009) For plants, however, reported changes seem to occur principally at the leading/front edge (Smith, 1994; Sturm et al., 2001; Walther et al., 2005b) without much clear evidence for changes at the trailing/rear edge (Lesica and McCune, 2004), in line with conclusions from an earlier review (Jump et al., 2009) on the apparent lack of latitudinal range shifts at the trailing/rear edge of plant species ranges, especially for long-lived plants such as woody species (Jump et al., 2009) Hitherto, most latitudinal range shifts have been documented in the Northern Hemisphere, with few studies focusing on the Southern Hemisphere (including Antarctica) (Table 1), consistent with previously suggested differences in observed climate-induced changes in natural and managed ecosystems between the Northern and Southern Hemispheres (IPCC, 2007a) Additionally, in the Northern Hemisphere, most latitudinal range shifts have been documented within the Arctic, boreal, temperate, and Mediterranean biomes, that is, from middle to high latitudes (Table 1) Only few studies of continental extent have covered tropical and subtropical areas below 301 latitude (Beaugrand et al., 2002; Hitch and Leberg, 2007; La Sorte and Thompson, 2007) Hence, there is a striking dearth of evidence for contemporary latitudinal range shifts from areas between –601 and 301 latitude (Table 1) The paucity of evidence from the Tropics and the Southern Hemisphere (except Antarctica) may have several explanations (IPCC, 2007a): (1) a marked scarcity of good historical data 603 from developing countries that are suitable for resampling along the latitudinal gradient between –601 and 301 latitude; (2) a lack of taxonomical knowledge, especially in the Tropics, making it difficult to study multispecies latitudinal range shifts; (3) logistic problems, making it even more difficult to collect, access, and manage ecological data in these regions of the world; (4) the fact that mean annual temperature within the Tropics is approximately constant between –211 and 211 latitude, at any given elevation, so that little opportunity for latitudinal escape from warming exists (Colwell et al., 2008); and (5) a huge imbalance of the Earth’s land mass distribution with relatively little terrestrial area between –601 and 01 latitude, which probably contributes to the paucity of evidence for contemporary latitudinal range shifts for terrestrial ecosystems at these latitudes Elevational Range Shifts A selective review of historically based studies documenting modern elevational range shifts was also carried out Although most studies have reported range shifts toward higher elevations for a majority of taxa (Table 2), these studies have also reported, to a lesser extent, unexpected range shifts toward lower elevations (Lenoir et al., 2010a) A few studies have even reported a general directional shift toward lower elevations for some taxonomic groups (Hickling et al., 2006; Crimmins et al., 2011) In Northern California, for instance, most plant species shifted downward to track regional changes in climatic water balance rather than temperature (Crimmins et al., 2011) This shows that range shifts may differ not only in extent, but also in direction due to regional variation in climate change Contrary to latitudinal range shifts, as many elevational range shifts have been reported for plants as for animals (Table 2) Across all taxonomic groups, elevational range shifts toward higher elevations have been documented through changes either at the trailing/rear edge (Wilson et al., 2005; Frei et al., 2010), the leading/front edge (Hickling et al., 2006; Frei et al., 2010), or the core (Konvicka et al., 2003; Lenoir et al., 2008) of species ranges Therefore, all possible patterns of upward shift between march- and lean-range shifts have been documented along the elevational gradient (Kelly and Goulden, 2008; Moritz et al., 2008; Raxworthy et al., 2008; Bergamini et al., 2009) However, it has been suggested that plants, especially long-lived plants such as woody species, are more likely to lean rather than march their elevational range upward (Breshears et al., 2008) Just as for latitudinal range shifts, there is a strong imbalance of evidence for observed elevational range shifts under contemporary climate change between the Northern and Southern Hemispheres, most likely due to the higher density of mountainous area in the Northern Hemisphere relative to the Southern Hemisphere Indeed, most elevational range shifts reports across taxonomic groups have been documented in the Northern Hemisphere, especially between 301 and 601 latitude (Table 2) Although there is a strong focus on temperate ecosystems in the Northern Hemisphere, most of the examples have been reported for subalpine, alpine, and nival ecosystems Therefore, research efforts on elevational range shifts have been focusing on the coldest biomes (Antarctic,