Showing papers in "Taxon in 1974"
272 citations
177 citations
TL;DR: A guide to the identification of the aquatic ferns and flowering plants of Australia, both native and naturalized, both naturalized.
Abstract: ASTON, H. I. Aquatic plants of Australia. A guide to the identification of the aquatic ferns and flowering plants of Australia, both native and naturalized. Illustrations chiefly by the author. Melbourne University Press I973 [p.o. Box 278, Carlton, South Carlton, Victoria 3053, Australia], 368 pp., I38 figs., 8i maps, I52 x 231/2 cm, buckram, publ. 6 September I973, ISBN 0-522-84044-2, price Austr. $ 21.-.
150 citations
TL;DR: It is suggested that the stomatal complex has value as a systematic character only in combination with a variety of other characters and only by consideration of groups which are already known to be natural.
Abstract: Summary Existing descriptions of patterns of stomatal development in monocotyledons are very few, often inaccurate and sometimes misleading. The terminologies developed therefrom are probably not very useful. In this article the situation is clarified with respect to information obtained from the examination of the development of the stomatal complex in about Ioo species of monocotyledons representing most families. Certain families lack divisions of cells surrounding the guard cell mother cell (meristemoid). Others possess such divisions which may be categorized as either oblique or non-oblique. Many families lack oblique divisions, others are characterized by oblique divisions. There seems to be a correlation between the presence of oblique divisions and the shortness of the protodermal cells. In some families the sequence of divisions is quite precise, in others it is quite variable. Available evidence shows that there are no major groups of monocotyledonous families characterized by a particular pattern of divisions in the development of the stomatal complex and that speculations about the phylogenetic significance of these patterns are premature. It is suggested that the stomatal complex has value as a systematic character only in combination with a variety of other characters and only by consideration of groups which are already known to be natural. Our present appreciation of the affinities of monocotyledonous groups should be used as a source of comparative information about the development of the stomatal complex in monocotyledons and not vice versa.
105 citations
TL;DR: Outcrossing rates in natural populations of Lupinus nanus Dougl.
Abstract: Summary Outcrossing rates in natural populations of Lupinus nanus Dougl. have been found to vary from nearly zero to nearly ioo percent (Harding and Horovitz, 1969; Harding, 1970). These studies were based primarily on a group of northern populations of subspecies apricus (Elliott, Harding, and Mankinen; paper VI). The purposes of this paper are (i) to report estimates of outcrossing for the other subspecies of L. nanus, (2) to report estimates of outcrossing for the closely related species, L. bicolor, L. affinis, L. polycarpus, and L. pachylobus, (3) to discuss the relationship between these estimates of outcrossing and autofertility, and (4) to discuss the relationship between outcrossing and phenotypic and genotypic variability maintained in populations. OUTCROSSING Rates of outcrossing have been estimated by progeny testing genetically recessive parents occurring in natural populations of Clarkia (Vasek, 1964, 1965, 1967), Avena (Jain and Marshall, 1967), and Lupinus (Harding and Horovitz, 1969; Harding, I970). In Lupinus nanus rare flower color mutants (Harding and Mankinen, 1967) are convenient genetic recessives for the estimation of outcrossing. These recessives are also found in the other species of the Nanus Group. The expected frequency of genetically dominant outcrosses arising in progeny of recessives is a(i-q) where a is defined as the frequency of outcrossing and q is the frequency of fertilizing male gametes having the recessive gene. If y is the observed frequency of dominant outcrosses in the progeny of recessive seed parents, the rate of outcrossing can be estimated by = y/(I-q) For the case of a rare recessive, q becomes small and a is approached by y. The approximation, a y, is sufficiently accurate for this study and will be used throughout. Each estimate will be presented with its standard error, which is given by sA=Vy(i-y)N, where N is the number of plants scored. Estimates of outcrossing based on progeny from variant flower color forms are likely to be biased underestimates of the outcrossing rates of wild-type flower color forms. However, the reduction was found to be
TL;DR: The genus is gynodioecious though in some species of Section Cortaderia only female plants are found, and recent treatments of the genus are substantially upheld.
Abstract: All valid names in Cortaderia Stapf (nom. cons.) are typified and recent treatments of the genus are substantially upheld. Taxa in Section Cortaderia are more precisely defined with no major nomenclatural changes except that C. jubata (Lem.) Stapf is regarded as the valid name for plants formerly known as "C. quila (Nees) Stapf". In Section Bifida, C. aristata and C. trianae are regarded as synonyms of C. bifida, and C. sodiroana as synonymous with C. nitida; C. minima is regarded as a synonym of C. pilosa. The new combination C. archboldii (Hitchcock) Connor and Edgar is based on Danthonia archboldii from New Guinea. The genus is gynodioecious though in some species of Section Cortaderia only female plants are found.
TL;DR: This paper presents a number of other examples in which species belonging to different subgenera are remarkably similar in gross leaf morphology, and in two of the more extreme examples speculations are advanced as to what the adaptive significance may be.
Abstract: Several cases are cited from the literature of misinterpretation of taxonomic relationships, where distantly related species of Quercus exhibit parallelism in leaf form. This paper presents a number of other examples in which species belonging to different subgenera are remarkably similar in gross leaf morphology. In each such example, the two species occur in very similar habitats, and actually co-exist in some areas. It is assumed that their similarities are adaptive, and in two of the more extreme examples speculations are advanced as to what the adaptive significance may be.
TL;DR: Variation was measured in samples of populations of species from four plant families including tropical, temperate and cosmopolitan taxa, showing distinct trends of within-group variation are consistent as they were revealed in the four families.
Abstract: Summary Variation was measured in samples of populations of species from four plant families including tropical, temperate and cosmopolitan taxa. Populations of species of Asclepiadaceae, Bromeliaceae, Leguminosae and Umbelliferae were sampled. Employing a simple application of numerical phenetics and tested character lists, estimates of within-group overall variation were made. The coefficients of phenetic variation (CPV) are compared among the various groups. The groups considered are populations as well as taxa at several levels in the classification hierarchy, although in all cases, individuals sampled randomly from putative populations are the operational taxonomic units (OTUs). A small number of individuals is employed with a large number of characters. This application of numerical phenetics serves both alpha taxonomic and biosystematic goals and an OTU x OTU matrix of distance values is the basis for obtaining estimates of a population's variability. The phenetic distances between OTUs are the variates. Distinct trends of within-group variation are consistent as they were revealed in the four families. Intrapopulational coefficient of phenetic variation for populations of the tropical family Bromeliaceae is estimated as nearly double that for the other three families. The intraspecific variation as portrayed by CPV in the Asclepiadaceae and Leguminosae is about half that for the tropical family, Bromeliaceae. As sampled a clear distinction is evidenced in the change in variation between various taxonomic ranks for the families. The difference in CPV between the intrapopulational and intraspecific levels for the Leguminosae and Bromeliaceae is nearly double the difference between these two ranks for the Asclepiadaceae. Results show that the method has descriptive and heuristic value for systematics.
TL;DR: Current methods in identification of biological specimens by computer cover construction of diagnostic keys, matching or comparison methods, and probabilistic methods related to Bayes' theorem.
Abstract: Summary The state of the art in identification of biological specimens by computer is reviewed. Current methods cover construction of diagnostic keys, matching or comparison methods, and probabilistic methods related to Bayes' theorem. There are also methods for reducing the number of characters that need to be used. The methods are compared and actual and possible progress is discussed.