03207nas a2200217   4500008004100000245008300041210006900124300001200193490000700205520257400212653001102786653002402797653002002821653001502841653002102856100001702877700002002894700001602914700001602930856004302946       2008                        eng d00aDoes species richness drive speciation? A reassessment with the Hawaiian biota0 aDoes species richness drive speciation A reassessment with the H  a279-2850 v313 aAfter MacArthur and Wilson (1967), island biogeographical research focused primarily on processes of colonization and extinction over ecological time scales, but recent work has rejuvenated interest in the generation of diversity in situ over evolutionary time (Lomolino 2000, Losos and Schluter 2000, Gillespie 2004, Cadena et al. 2005). In a recent contribution, Emerson and Kolm (2005) proposed a causal link between species richness and speciation on islands. They suggested that species richness per se might increase the rate of speciation by intensifying competition and suppressing population densities of resident species, thereby allowing for increased genetic drift, greater lability in traits, and increased evolutionary change (Erwin 2005). Alternatively, increased structural complexity and heterogeneity associated with higher richness may stimulate niche diversification and speciation (Tokeshi 1999).In this paper, we revisit the relationship between endemism and species richness in a reanalysis of arthropod (Nishida 2002) and plant (Price 2004) data for the Hawaiian Islands and include a new dataset for land snails (Cowie et al. 1995, Cowie and Holland 2006). We propose distinct null models for endemism patterns in these island datasets. Because the methodological contrasts and findings of these different null models are more clear in the context of our assumptions, methods, and results, we address the specific null models of Emerson and Kolm (2007a,b), Witt and Maliakal-Witt (2007), Kiflawi et al. (2007), and Birand and Howard (2008) following the discussion of our analyses.Emerson and Kolm's (2005) original regression analysis rested on the implicit assumption that, in the absence of driving speciation mechanisms, the number or proportion of endemic species should be independent of the total richness on individual islands (this assumption was later made explicit, Emerson and Kolm 2007a). Under this assumption, the statistical null hypothesis is of no correlation between the proportion of SIEs and total species richness. However, a universal property of biodiversity sampling curves is that rare species are disproportionately under-represented in small samples (Gotelli and Colwell 2001). At the biogeographic scale, we expect the proportion of SIEs to escalate with total species richness, even in the absence of mechanisms promoting in situ speciation. Therefore, we formulated two null sampling hypotheses that incorporated the expected non-linearity in SIE proportion with variation in the richness of island species pools.10aHAWAII10aisland biogeography10aPacific Insects10aSPECIATION10aspecies richness1 aGruner, D.S.1 aGotelli, N., J.1 aPrice, J.P.1 aCowie, R.H.  uhttps://pacleps.myspecies.info/node/77