On the Parsimony of Some Model-Selection Criteria in Econometric Modeling

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Embryo retention,character optimization,and the origin of the extra‐embryonic membranes of the amniotic egg

This study summarizes the data relevant to understanding the appearance of the amniotic egg and provides new analyses to determine the inferences that can be drawn from these data. A survey of the recent literature shows that a consensus exists on the probably primitive absence of extended embryo retention in caecilians, despite recent suggestions to the contrary. The two most recent studies on the evolution of embryo retention in sarcopterygians both suggest that early amniotes lacked extended embryo retention. New analyses of length distribution of random trees suggest that the data on embryo retention do not include a phylogenetic signal, and this implies that character optimization of these data does not yield reliable information on the primitive condition for amniotes. Thus, the study of ancestral features of amniotes will probably have to exploit data from the fossil record.     

Caecilian viviparity and amniote origins

A recent evaluation of alternative hypotheses for the origin of the amniotic egg, by mapping a single reproductive-mode character onto a phylogeny of tetrapods, concluded that the alternative hypotheses were equally parsimonious. However, this interpretation is dependent upon a mistaken coding of the caecilian amphibians as showing extended embryo retention. Although some caecilians are viviparous, phylogenetic analyses indicate that oviparity is ancestral for the group. With the coding of caecilians corrected, the most parsimonious inference is that the ancestral amniotes did not practice extended embryo retention. A review of the available data indicates that the widespread view that a majority of caecilians are viviparous is mistaken. Oviparity is the dominant reproductive mode in caecilians as it is in other living amphibians.     

First observations on the phylogeny of the families Gammaridae,Crangonyctidae, Melitidae,Niphargidae, Megaluropidae and Oedicerotidae (Amphipoda,Crustacea), using small subunit rDNA gene sequences

This study examines amphipod phylogeny based on small subunit (18S) rDNA sequence data. Complete sequences of 25 species representing six families were used to test the phylogenetic information content of this gene for reconstruction of amphipod phylogeny. The alignment proved to be informative for most of the studied taxa. The monophyly of the families Gammaridae, Crangonyctidae, Niphargidae and Oedicerotidae is supported. The Melitidae are not monophyletic in the reconstructed topologies, but weak molecular evidence for the monophyly of this group could be observed in spectra of supporting positions. A close relationship of Gammaridae + Melitidae or Gammaridae + Crangonyctidae is not supported, rather there are supporting positions for the incompatible sister-group relationship (Gammaridae + Niphargidae) and (Crangonyctidae + Niphargidae). The molecular evidence is in favour of the latter relationship. The evolution of cephalothoracic apodemes is discussed in the light of other phylogenetic hypotheses resulting from molecular data.     

Consensus phylogeny ofDictyostelium

The evolutionary relationship ofDictyostelium discoideum to the yeasts, fungi, plants, and animals is considered on the basis of physiological, morphological and molecular characteristics. Previous analyses of five proteins indicated thatDictyostelium diverged after the yeasts but before the metazoan radiation. However, analyses of the small ribosomal subunit RNA indicated divergence prior to the yeasts. We have extended the molecular phylogenetic analyses to six more proteins and find consistent evidence for a more recent common ancestor with metazoans than yeast. A consensus phylogeny generated from these new results by both distance matrix and parsimony analyses establishesDictyostelum's place in evolution between the yeastsSaccharomyces cerevisiae andSchizzosaccharomyces pombe and the wormCaenorhabditis elegans.     

分支分类学中的数值简约性原则

数值简约性原则是分支分类学进行分支分析及重构生物演化分支图的主要思想方法。本文着重阐述数值简约性原则的基本概念，应用方法，及其在植物系统发育研究中的实际意义。同时具体展示了从原始数据矩阵到完成构建分支图的整个过程。最后讨论了数值简约性原则在应用过程中值得注意的几个问题。     

从可能性视角对分支简单性的探讨

分支系统学是一种建立在进化树分支模式基础上通过共同祖先为生物分类的方法。美国当代著名科学哲学家艾利奥特.索伯(Elliott Sober)论证了可证伪性对分支系统学合理性辩护的不足之处,指出假说-推理方法的局限性。在此基础上,从可能性的角度探讨了分支简单性与可能性的关系。