Frogs of the genus Rana are among the most commonly studied vertebrates in laboratories worldwide. In primary schools, children often learn about reproduction and development by watching the fertilization of Rana eggs and the growth of...
moreFrogs of the genus Rana are among the most commonly studied vertebrates in laboratories worldwide. In primary schools, children often learn about reproduction and development by watching the fertilization of Rana eggs and the growth of the resulting embryos into tadpoles. In secondary schools, many young biologists-to-be are introduced to anatomy and physiology by dissecting pithed Rana. In college, students may encounter Rana in endocrinology, comparative anatomy, vertebrate physiology, and embryology classes. In addition, ongoing laboratory research on Rana spans virtually all fields of biology. So it is both surprising and unfortunate that study of the natural history and systematics of Rana has lagged far behind experimental laboratory studies. As this deficiency gradually has been corrected, the changes in interpretation of past laboratory studies have been profound. In Europe, the common edible frog ("R. esculenta") is now known to be a hybridogenetic form (113), a finding that will considerably alter the conclusions of much of the developmental, genetic, and physiological work conducted with this species. In North America, "the frog" in experimental studies usually has been a leopard frog, R. pipiens. Unfortunately, past studies that referred to R. pipiens may have involved any of a complex of approximately two dozen different species, which in spite of their morphological similarity are genetically, physiologically, and behaviorally quite distinct (26, 44, 56). The R. pipiens complex has served through the years as a textbook example in discussions of systematics for several distinct reasons. Until the 1960s, R. pipiens was commonly cited in introductory biology and evolution textbooks
The use and misuse of various measures of genetic" distance" in electrophoretic studies of systematics have recently been the subject of considerable attention (Mickevich and Johnson, 1976;...
moreThe use and misuse of various measures of genetic" distance" in electrophoretic studies of systematics have recently been the subject of considerable attention (Mickevich and Johnson, 1976; Throckmorton, 1978; Baverstock et al., 1979; Avise et al., 1980; Farris, 1981; Mickevich and Mitter, 1981; Patton et al., 1981; Sites et al., 1981; Thorpe, 1982). Despite the problems associated with the use of genetic distances in the construction of phylogenetic trees, the convenience and general utility of such measures have resulted in their ...
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How are endangered species discovered? How can they save a city? Barton Springs is a resource unique to Austin drawing thousands of visitors every year. Yet, Barton Springs is home to endangered species of salamanders rarely seen by the...
moreHow are endangered species discovered? How can they save a city? Barton Springs is a resource unique to Austin drawing thousands of visitors every year. Yet, Barton Springs is home to endangered species of salamanders rarely seen by the public. In the early 1990s, Dr. David Hillis, a professor at The University of Texas, discovered the Barton Springs salamander. Dr. Hillis will share how the Barton Springs salamander was identified as an endangered species and its impact in Austin’s economic development. Live animals, including the Barton Springs salamander, will be present during the Community Science Fair.
The Wageningen UR Library Catalogue contains bibliographic data on books and periodicals held by the libraries of Wageningen University and Research Centre and some 15 associated libraries. Holding data are added to each record. ......
moreThe Wageningen UR Library Catalogue contains bibliographic data on books and periodicals held by the libraries of Wageningen University and Research Centre and some 15 associated libraries. Holding data are added to each record. ... Subjects covered include Agrotechnology, Food and Food Production, Plant and Animal Sciences, Soil Science, Geo-information, Landscape and Spatial Planning, Water and Climate, Ecosystem Studies, Economics and Society. ... The joint collections of the participating libraries cover a substantial part of ...
Hyla favosa, Hyla leucophyllata, and phenotypic intermediates between these species were discovered in microsympatry in southeastern Peru. The genetic composition of individuals of all three phenotypes was analyzed using starch-gel...
moreHyla favosa, Hyla leucophyllata, and phenotypic intermediates between these species were discovered in microsympatry in southeastern Peru. The genetic composition of individuals of all three phenotypes was analyzed using starch-gel protein electrophoresis to test the validity of species level status for H. favosa and H. leucophyllata. Twenty-two presumptive gene loci were scored. No alleles diagnostic of the two pure phenotypes were found. Phenotypic intermediates were genetically indistinguishable from the two pure forms and ...
For sample chapters, a video interview with David Hillis, and more information, visit
www. whfreeman. com/hillispreview. Sinauer Associates and WH Freeman are proud to introduce Principles of Life. Written in the spirit of the reform...
moreFor sample chapters, a video interview with David Hillis, and more information, visit
www. whfreeman. com/hillispreview. Sinauer Associates and WH Freeman are proud to introduce Principles of Life. Written in the spirit of the reform movement that is reinvigorating the introductory majors course, Principles of Life cuts through the thicket of excessive detail and factual minutiae to focus on what matters most in the study of biology today. Students explore the most essential biological ideas and information in the context of the field's ...
BACKGROUND Fitch (1979) and Goodman et al.(1979a) were among the first authors to explore tree-length distributions in a phylogenetic context. These authors compared the relative phylogenetic information in two protein sequence data sets...
moreBACKGROUND Fitch (1979) and Goodman et al.(1979a) were among the first authors to explore tree-length distributions in a phylogenetic context. These authors compared the relative phylogenetic information in two protein sequence data sets that had been used to infer relationships among orders of mammals. As can be seen in Figure 13-1, the distribution of tree lengths from the a-hemoglobin sequences is nearly perfectly symmetrical, whereas that from the a-crystallin sequences is strongly skewed with a long left tail. Therefore, there ...
Summary Each year an international panel of virology experts must recommend which flu virus strains to include in the preparation of the vaccine to combat the upcoming flu season. As Hillis explains in his Perspective, this tough...
moreSummary Each year an international panel of virology experts must recommend which flu virus strains to include in the preparation of the vaccine to combat the upcoming flu season. As Hillis explains in his Perspective, this tough challenge should be made easier by the finding that those viral strains showing the greatest number of substitutions among amino acids in the HA1 domain of hemagglutinin (the spike-like protein on the viral surface that elicits an immune response) are more likely to contribute to future flu epidemics (Bush et ...
In Jan. 1984 we investigated other river systems in northeastern Mixico for evidence of Corbicula (Fig. 1). We found populations of what appear to be both the white and purple forms of Corbicula in the Rio San Juan and Rio Soto la Marina...
moreIn Jan. 1984 we investigated other river systems in northeastern Mixico for evidence of Corbicula (Fig. 1). We found populations of what appear to be both the white and purple forms of Corbicula in the Rio San Juan and Rio Soto la Marina drainages (Rio San Juan at Castillos, Nuevo Leon, 100 01'W, 25 33'N; unnamed tributary 3 km south of Rio Corona crossing of Mex. Hwy. 101, Tamaulipas, 98057'W, 23057'N. Between the Rio San Juan and Rio Soto la Marina drainages is the Rio San Fernando drainage which appears to contain ...
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Summary Phylogenetic analysis--the study of the evolutionary relationships of organisms--is enjoying something of a renaissance. In his Perspective, Hillis discusses this trend, exemplified in this issue in two reports by Pierce et al.(p....
moreSummary Phylogenetic analysis--the study of the evolutionary relationships of organisms--is enjoying something of a renaissance. In his Perspective, Hillis discusses this trend, exemplified in this issue in two reports by Pierce et al.(p. 256) and Becerra (p. 253) that examine the evolution of enzymes and host-pest pairs and in an article by Huelsenbeck et al.(p. 227) that discusses current methods of phylogenetic analysis.
In some reptiles, egg incubation temperature determines whether the embryo hatches as male or female; in others, sex chromosomes determine sex. A cloned gene (ZFY) representing the putative testis-determining factor in mammals was...
moreIn some reptiles, egg incubation temperature determines whether the embryo hatches as male or female; in others, sex chromosomes determine sex. A cloned gene (ZFY) representing the putative testis-determining factor in mammals was hybridized to genomic DNA of reptiles with sex chromosomes and to DNA of reptiles with temperature-dependent sex determination. No sex differences in hybridization patterns were observed. Hybridization
Williams et al.(1988) commented on the use of ribosomal DNA (rDNA) in systematic studies. Although we share their desire for greater rigor in systematic studies of rDNA, many of their points are inaccurate or misleading. Specifically,...
moreWilliams et al.(1988) commented on the use of ribosomal DNA (rDNA) in systematic studies. Although we share their desire for greater rigor in systematic studies of rDNA, many of their points are inaccurate or misleading. Specifically, Williams et al. inaccurately report and interpret data presented by us (Hillis and Davis, 1986), and misrepresent both the effects of concerted evolution on phylogenetic analyses and the use of heterologous molecular probes. Williams et al.(1988) note that the nontranscribed spacer (NTS) of rDNA evolves ...
Publisher Summary The chapter discusses phylogenetic inference for the analysis of DNA sequence data. There are five basic steps in the phylogenetic analysis of DNA sequences. The sequences under study must first be aligned so that...
morePublisher Summary The chapter discusses phylogenetic inference for the analysis of DNA sequence data. There are five basic steps in the phylogenetic analysis of DNA sequences. The sequences under study must first be aligned so that positional homologs (the units of comparison) may be analyzed. Alignment may be straightforward if pairwise differences are small and most differences result from substitutions but it becomes increasingly difficult as the sequences become more divergent and insertion/deletion events become more common. Once sequences are aligned, some assessment of the presence of phylogenetic signal is necessary. If phylogenetic signal is present in a matrix of sequences, then the third step is selecting a method of phylogenetic inference. Once a method has been selected and the appropriate software has been obtained, a strategy must be developed for finding the best tree under the selected optimality criterion. Once a tree has been obtained, some statement of confidence in the results is desirable, such as deciding which nodes of the tree are well-supported by the data, and which are not.
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moreNature Publishing Group, publisher of Nature, and other science journals and reference works, Advertisement. nature.com, about npg,
news@nature.com, naturejobs, natureevents, help, site index, my account, e-alerts, subscribe, register. SEARCH JOURNAL. Friday 23 March 2012. Journal Home, Current Issue, AOP, Archive, THIS ARTICLE, Download PDF, References, Export citation, Export references, Send to a friend, More articles like this, Table of Contents, < Previous | Next >, Nature 369, 363 - 364 (02 June 1994); doi: Hobgoblin of phylogenetics ...