151,968 research outputs found

    Coccinia intermedia

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    Nuclear and plastid sequences from two individuals of a suspected new species of Coccinia from West Africa were added to an available molecular phylogeny for the remaining 27 species of the genus. Phylogenetic analyses of these data indicate the new species' monophyletic status and closest relatives. Based on four fertile collections, we here describe and illustrate Coccinia intermedia Holstein. We also provide a key to the Coccinia species of West Africa and map their distributions

    W(h)ither Fossils? Studying Morphological Character Evolution in the Age of Molecular Sequences

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    A major challenge in the post-genomics era will be to integrate molecular sequence data from extant organisms with morphological data from fossil and extant taxa into a single, coherent picture of phylogenetic relationships; only then will these phylogenetic hypotheses be effectively applied to the study of morphological character evolution. At least two analytical approaches to solving this problem have been utilized: (1) simultaneous analysis of molecular sequence and morphological data with fossil taxa included as terminals in the analysis, and (2) the molecular scaffold approach, in which morphological data are analyzed over a molecular backbone (with constraints that force extant taxa into positions suggested by sequence data). The perceived obstacles to including fossil taxa directly in simultaneous analyses of morphological and molecular sequence data with extant taxa include: (1) that fossil taxa are missing the molecular sequence portion of the character data; (2) that morphological characters might be misleading due to convergence; and (3) character weighting, specifically how and whether to weight characters in the morphological partition relative to characters in the molecular sequence data partition. The molecular scaffold has been put forward as a potential solution to at least some of these problems. Using examples of simultaneous analyses from the literature, as well as new analyses of previously published morphological and molecular sequence data matrices for extant and fossil Chiroptera (bats), we argue that the simultaneous analysis approach is superior to the molecular scaffold approach, specifically addressing the problems to which the molecular scaffold has been suggested as a solution. Finally, the application of phylogenetic hypotheses including fossil taxa (whatever their derivation) to the study of morphological character evolution is discussed, with special emphasis on scenarios in which fossil taxa are likely to be most enlightening: (1) in determining the sequence of character evolution; (2) in determining the timing of character evolution; and (3) in making inferences about the presence or absence of characteristics in fossil taxa that may not be directly observable in the fossil record. Published By: Missouri Botanical Garde

    Third-codon transversion rate-based _Nymphaea_ basal angiosperm phylogeny -- concordance with developmental evidence

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    Flowering plants (angiosperms) appeared on Earth rather suddenly approximately 130 million years ago and underwent a massive expansion in the subsequent 10-12 million years. Current molecular phylogenies have predominantly identified _Amborella_, followed by _Nymphaea_ (water lilies) or _Amborella_ plus _Nymphaea_, in the ANITA clade (_Amborella_, Nymphaeales, Illiciaceae, Trimeniaceae and Austrobaileyaceae) as the earliest angiosperm. However, developmental studies suggest that the earliest angiosperm had a 4-cell/4-nucleus female gametophyte and a diploid endosperm represented by _Nymphaea_, suggesting that _Amborella_, having an 8-cell/9-nucleus female gametophyte and a triploid endosperm, cannot be representative of the basal angiosperm. This evolution-development discordance is possibly caused by erroneous inference based on phylogenetic signals with low neutrality and/or high saturation. Here we show that the 3rd codon transversion (P3Tv), with high neutrality and low saturation, is a robust high-resolution phylogenetic signal for such divergences and that the P3Tv-based land plant phylogeny cautiously identifies _Nymphaea_, followed by _Amborella_, as the most basal among the angiosperm species examined in this study. This P3Tv-based phylogeny contributes insights to the origin of angiosperms with concordance to fossil and stomata development evidence

    Dental eruption in ruminants and other mammals

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