852 A. Colles, L. H. Liow and A. Prinzing Review and Synthesis Table 2 (a) Are specialists at risk of decline? This is a tabulation of the results of our literature review (see Appendix S1) on the relationship between specialization and decline We ﬁrst show the number and percentages of studies in neoecology, paleoecology and phylogenetic studies that conclude specialization is positively correlated with the risk of decline. Then we break these up into whether the studies fulﬁlled criteria as discussed and numbered in Table 1. These criteria are summarized in column 1. Note that criterion 4 has not been fulﬁlled by any of the studies we reviewed and is hence omitted. A plus sign (+) indicates that the given criterion is fulﬁlled and a negative sign ()) indicates that it is not. Each cell gives the percentage and numbers of studies in parentheses. Shaded cells highlight current limitations: more than half of the studies do not fulﬁll the criterion. Dark shading indicates that for the respective approach (neoecology ⁄ paleoecol- ogy ⁄ phylogeny) the limitation is stronger than for other approaches, i.e. comparing cells within a line (chi-square test; P < 0.05). Coloured bordered boxes and numbers indicate biases, i.e. studies that do not fulfill the criterion or that do fall into the overrepresented category give overly negative (dark red) or a positive (light blue) results regarding the effect of specialization (+, *; **; *** = P < 0.1, 0.05, 0.01, 0.001, chi-square test). Some of the phylogenetic studies cover both phylogenetic hypotheses mentioned, and are thus counted in both columns 5 and 6. In the text, we refer to specific lines in this table by their row numbers (1–3 and 5–9) and signs (+ ⁄ )). (b) Are specialists at risk of decline? (Colour coding described above). Here, we show the number and percentages of studies in neoecology, paleoecology and phylogenetic studies that conclude specialization is positively correlated with the risk of decline in different study systems and with respect to the type of specialization studied. 2009 Blackwell Publishing Ltd/CNRS