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Allopatry is conventionally considered the geographical mode of speciation for continental island organisms. However, strictly allopatric speciation models that assume the lack of postdivergence gene flow seem oversimplified given the recurrence of land bridges during glacial periods since the late Pliocene. Here, to evaluate whether a continental island endemic, the Taiwan hwamei (Leucodioptron taewanus, Passeriformes Timaliidae) speciated in strict allopatry, we used weighted-regression-based approximate Bayesian computation (ABC) to analyse the genetic polymorphism of 18 neutral nuclear loci (total length: 8500 bp) in Taiwan hwamei and its continental sister species, the Chinese hwamei (L. canorum canorum). The nonallopatry model was found to fit better with observed genetic polymorphism of the two hwamei species (posterior possibility = 0.82). We also recovered unambiguous signals of nontrivial bidirectional postdivergence gene flow (N(e)m >> 1) between Chinese hwamei and Taiwan hwamei until 0.5 Ma. Divergence time was estimated to be 3.5 to 2 million years earlier than that estimated from mitochondrial cytochrome b sequences. Finally, using the inferred nonallopatry model to simulate genetic variation at 24 nuclear genes examined showed that the adiponectin receptor 1 gene may be under divergent adaptation. Our findings imply that the role of geographical barrier may be less prominent for the speciation of continental island endemics, and suggest a shift in speciation studies from simply correlating geographical barrier and genetic divergence to examining factors that facilitate and maintain divergence, e.g. differential selection and sexual selection, especially in the face of interpopulation gene flow.

This paper is concerned with designing experiments under the assumption that an analysis strategy is used that considers interactions in addition to main effects. A criterion which averages an approximation to A s-efficiency over lower-dimensional projections of the design is introduced to compare designs. A columnwise design procedure is used to construct three-level designs for six factors in 18 runs. The projection efficiencies of these designs are explored and compared with designs obtained from the L 18 orthogonal array. Results are also given for designs with 14 and 17 runs.

Although founder effect speciation has been a popular theoretical model for the speciation of geographically isolated taxa, its empirical importance has remained difficult to evaluate due to the intractability of past demography, which in a founder effect speciation scenario would involve a speciational bottleneck in the emergent species and the complete cessation of gene flow following divergence. Using regression-weighted approximate Bayesian computation, we tested the validity of these two fundamental conditions of founder effect speciation in a pair of sister species with disjunct distributions: the royal spoonbill Platalea regia in Australasia and the black-faced spoonbill Pl. minor in eastern Asia. When compared with genetic polymorphism observed at 20 nuclear loci in the two species, simulations showed that the founder effect speciation model had an extremely low posterior probability (1.55 × 10(-8)) of producing the extant genetic pattern. In contrast, speciation models that allowed for postdivergence gene flow were much more probable (posterior probabilities were 0.37 and 0.50 for the bottleneck with gene flow and the gene flow models, respectively) and postdivergence gene flow persisted for a considerable period of time (more than 80% of the divergence history in both models) following initial divergence (median = 197,000 generations, 95% credible interval [CI]: 50,000-478,000, for the bottleneck with gene flow model; and 186,000 generations, 95% CI: 45,000-477,000, for the gene flow model). Furthermore, the estimated population size reduction in Pl. regia to 7,000 individuals (median, 95% CI: 487-12,000, according to the bottleneck with gene flow model) was unlikely to have been severe enough to be considered a bottleneck. Therefore, these results do not support founder effect speciation in Pl. regia but indicate instead that the divergence between Pl. regia and Pl. minor was probably driven by selection despite continuous gene flow. In this light, we discuss the potential importance of evolutionarily labile traits with significant fitness consequences, such as migratory behavior and habitat preference, in facilitating divergence of the spoonbills.

We propose a general and unified approach to the selection of regular fractional factorial designs which can be applied to experiments that are unblocked, blocked, with random or fixed block effects, or have a split-plot structure. Our criterion is derived as a good surrogate for the model-robustness criterion of information capacity. In the case of random block effects, it takes the ratio of intra-and interblock variances into account. In most of the cases, up to 32 runs, we have examined, there exist designs that are optimal for all values of that ratio. Examples of optimal designs that depend on the ratio are provided. We also demonstrate that our criterion can further discriminate designs that cannot be distinguished by the existing minimum-aberration criteria.

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Recent work on multistratum fractional factorial designs is set in a general and unified framework, and a criterion for selecting multistratum fractional factorial designs that takes stratum variances into account is proposed. Application of the general theory is illustrated on designs of experiments with multiple processing stages, including split-lot designs, blocked strip-plot designs, and post-fractionated strip-block designs. In particular, this helps elucidate the relationship between the three different design settings studied by Miller (1997), Bingham et al. (2008), and Vivacqua and Bisgaard (2009). The construction and selection of two-stage designs in these settings are shown to be equivalent. Good designs based on our criterion are found and compared with those tabulated in Vivacqua and Bisgaard (2009).

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