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Table 1 . Estimates of fixed effects, with standard errors, from univariate models and a multivariate model to explain crossing success in Ruellia (Acanthaceae). A negative coefficient for Allopatry vs. Sympatry indicates reduced crossing success in sympatry relative to allopatry. Genetic distance is measured as the branch length separating two species in a maximum likelihood phylogeny. Asterisks indicate significance levels from likelihood ratio tests that (1) compare the likelihood of a model with just the single fixed effect and random effects for donor and species identity versus a null model with only random or (2) compare the likelihood of the full model with all fixed effects and random effects versus a model without the given fixed effect [p < 0.05 *, p < 0.01 **, p < 0.001 ***].