@ARTICLE{TreeBASE2Ref18697, author = {Eric Schuettpelz and Sara B. Hoot}, title = {Inferring the root of Iso?tes: exploring alternatives in the absence of an acceptable outgroup}, year = {2006}, keywords = {}, doi = {10.1600/036364406777585856}, url = {}, pmid = {}, journal = {Systematic Botany}, volume = {31}, number = {2}, pages = {258--270}, abstract = {The ancient divergence between the lycopsid genus Iso?tes and its closest living relative (Selaginella) has resulted in considerable morphological and genetic disparity, yet within Iso?tes there is remarkable morphological and genetic uniformity. This has made it difficult to identify the phylogenetic root of the genus. In this study, we addressed this problem and characterized the early branching patterns within Iso?tes using an expanded set of taxa and three molecular markers. We assessed the saturation in the molecular data sets, tested for differences in evolutionary rate, determined the stability of the ingroup topology, and evaluated the applicability of the molecular clock. We then explored three alternative rooting approaches: outgroup, midpoint, and maximum likelihood under the assumption of a molecular clock. Attempts to infer the root of Iso?tes using the outgroup approach were severely hindered by the effects of saturation, but the results from midpoint rooting and the enforcement of the molecular clock were highly consistent among the data sets. We identify the root of Iso?tes to be located among three major, highly supported clades.} }

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