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Because systematic studies based on morphology have failed to fully resolve phylogenetic relationships of shanks (Charadriiformes: Scolopacidae), we obtained mitochondrial DNA (6349 bp) and nuclear DNA (1315 bp) sequences from 15 taxa. Using maximum parsimony and Bayesian analysis we show that Catoptrophorus and Heteroscelus are embedded within Tringa, and thus these genera should be merged in Tringa. Phylogenetic analyses of 18 morphological characters resulted in a partly resolved tree, so we mapped them on the molecular phylogeny and reconstructed ancestral states by maximum likelihood. Twelve of the morphological characters are homoplastic or plesiomorphic, and only six are phytogenetically informative, placing Xenus and Actitis outside the remaining genera. The bright yellow and red leg coloration of yellowlegs and redshanks are, respectively, a retained ancestral state and a parallel acquisition. Using a semi-parametric penalized-likelihood approach to correct for rate variation among lineages we estimated that speciation occurred in the Early Miocene-Pliocene. Key words: ancestral states, divergence time, parallel evolution, plesiomorphy, Scolopacidae, shanks, systematics.

We employed Bayesian coalescent modeling of samples of mitochondrial control region sequences in two species of shorebird, Red Knots (Calidris canutus) and Dunlins (Calidris alpina) to estimate evolutionary effective population size, population divergence times, and time to most recent common ancestor of genes in the samples. The gene trees for the two species contrast sharply: knot haplotypes were connected in a shallow, star phylogeny whereas Dunlin haplotypes were related in a deeper bifurcating genealogy. Divergence times of populations representing all six subspecies of knots are estimated to have occurred within the last 20 000 (95% CI: 5600-58 000) years, and evolutionary effective population sizes of females are small ([N.sub.ef] = 2000-14 000). We hypothesized that breeding knots were restricted to unglaciated regions of Eurasia during the last glacial maximum, and gradually expanded eastwards into Alaska, the high Canadian Arctic and Greenland as the ice melted. Population divergence times in Dunlins are much older (58 000-194 000 ybp) and effective population size has historically been higher in major lineages ([N.sub.ef] = 12 000-44 000). We conclude that Dunlin populations were not severely reduced in size in the last 200 000 years, and major lineages have differentiated under restricted gene flow for a much longer time than knots. Knots present a snapshot of genetic evolution in the last 20 000 years, whereas Dunlins display patterns of genetic evolution over ah order of magnitude longer time frame. Key words: Calidris alpina, Calidris canutus, coalescent theory, control region, mitochondrial DNA, phylogeography.