Showing papers in "Taxon in 1981"

Infrageneric classification of helianthus (compositae)

Abstract: Summary A formal infrageneric classification for the genus Helianthus is presented. The classification was derived using phenetic, cladistic and biosystematic procedures. The 49 species of Helianthus are placed into four sections and seven series.

Quantitative biogeography: an overview

Abstract: Biogeography is currently in an exciting, challenging, revolutionary stage. Quantitative biogeography, both at the historical and ecological levels, will play an increasingly important role because rapidly increasing amounts of data will require quantitative methods and computer analysis. An effective way to comprehend quantitative methods and to determine when they can be effective is to consider any biogeographic study as a multistage decision process. Not only does this provide a framework for such activities, but it also emphasizes that one's conclusions are affected by decisions made at different stages of the study. The best perspective is that biogeography is an unending synthesis, both of many types of theories and of many types of data and analyses to test them. A corollary to this approach is that no single method or analysis can answer all questions of biogeographic interest. Finally, while computers and quantitative analyses can enhance the human mind, they can never replace it.

Distribution of gametophytic self‐incompatibility and infrageneric classification in solanum

Abstract: Self-incompatibility in Solanum appears to be largely restricted to species of subgenus Potatoe, providing further support for the separation of that group from subgenus Solanum. Loss of self-incompatibility must have taken place early in the evolutionary histories of other subgenera. Possible adaptations for outcrossing, such as enantiostyly, dioecy and to a restricted degree, secondary self-incompatibility, have subsequently arisen in certain members of these predominantly self-compatible groups. The distribution of unilateral cross-incompatibility in Solanum seems to parallel that of self-incompatibility.

Studies on manganese‐accumulating alyxia species from new caledonia

Abstract: Thirty-one species of Alyxia from New Caledonia were analysed for their manganese content. Most of the species showed excessive uptake of manganese with a maximum of 1.15% Mn in dried leaves of A. rubricaulis. The manganese content alone was sufficient to distinguish a number of species from each other. Composite samples were in addition analysed for calcium, magnesium, potassium and sodium. Correlation analysis and calculation of the slopes of regression lines showed that manganese uptake was mainly at the expense of calcium, rather than magnesium. Similarly magnesium was preferred to potassium and potassium to sodium. It is possible that manganese may have some physiological role in Alyxia, compensating to some extent for reduced uptake of the nutrients calcium and potassium.

Evolutionary history of the old world lupines

Abstract: Summary About twelve species of Lupinus are centered in the Mediterranean and North African parts of the Old World. They show limited morphologocal polymorphism, but they are diverse in other ways. The group as a whole features three unique characteristics of evolutionary significance: (a) a special geographical distribution, disjunct from the main center in America, with allopatric rough-seeded and partially sympatric smooth-seeded species; (b) karyotype polymorphism, with at least seven different chromosome numbers, none of which has been encountered in the New World; (c) systematic disassociation, by which most species are taxonomically unrelated and genetically isolated. This cyto-geographical complex pattern and systematic divergence are best understood on the assumption that a few lupines of various origins migrated by means of long-range dispersal from their primary center in North America during the Neogene. The migrations were repeated quite haphazardly. Rough-seeded migrules were established in NW Africa, while smooth-seeded ones arrived at the Mediterranean, probably later on. During the Miocene lupine populations spread and diverged along the Mediterranean and in Africa north of the equator, succeeding the Tethyan flora. Their present eco-geographical distribution is the outcome of both climatic and edaphic changes during the Quaternary, combined with the impact of human activities from the Pleistocene on. Whereas the evolution of Lupinus in the New World has been enhanced by processes such as ecological differentiation and intensive hybridization, that of the Old World lupines has been inhibited owing to rapidly increasing aridity and civilization. The main changes in the gene pool of wild populations could be caused by disruptive differentiation, i.e., occasional hybridization and subsequent intergradations with escaped or neglected, sporadically

Wagner networks and wagner trees: a presentation of methods for estimating most parsimonious solutions

Abstract: The methods of Wagner network and Wagner tree construction are presented. A worked example, based on a set of hypothetical taxa, is examined in detail. Additional examples, representing real and artificial data sets, are also examined. The existence of alternative choices at several stages in the algorithms leads to solutions that may not be most parsimonious estimates. There apparently is no non-arbitrary method for choosing between the alternatives. The examples presented illustrate that there may be multiple equally parsimonious solutions for a given data set and that neither algorithm can ensure a most parsimonious solution.

Microwave: a method to control herbarium insects

Abstract: Summary The use of a microwave oven to treat herbarium specimens as a means of fumigation is discussed. Insects which ingest dried plants are of worldwide distribution and can be found in unprotected herbaria everywhere. Protection from these insects, which destroy or damage dried plant collections, has been a continual source of problems. Most methods of destroying the insects are dangerous to humans, unnecessarily time consuming, or both (Croat, 1978; Schofield and Crisafulli, 1980). However, use of a microwave oven to treat herbarium specimens is quick, safe, and sure.3 Live insects have considerable amounts of liquid within their tissues; on the other hand, dried plants in general contain little or no liquid. The microwave oven emits radiations at 2450 MHz/sec to agitate water and/or fat molecules. Friction caused by this agitation creates heat which then kills the insects at all stages of their life cycle. Since the dried plants retain little or no liquid they are not heated or harmed by this treatment. Use of the microwave oven has obvious advantages over toxic fumigants in that there are no dangerous fumes or vapors. Ovens occupy very little space, are available in a variety of sizes to accommodate nearly all herbarium sheets in use, and attach readily to existing electrical service mains. Another practical use of this quick method is to disinfest collections or specimens that will be in the herbarium for only a short while. Those individuals who have specimens for immediate identification and visiting botanists who hand carry specimens but will only be present in the herbarium for a few hours or days would benefit from this time saving procedure while the regular herbarium collections are protected from inadvertent infestations. After microwaving, a low level [30 g (1 oz) per full size case] of paradichlorobenzene or appropriate levels of other chemical fumigants, such as Drione (Fairfield American Corporation, 3932 Salt Road, Medina, New York 14103) (Schofield and Crisafulli, 1980), in herbarium cases deters the insects but does not prevent an infestation. If a case becomes infested, which would be seldom if given proper care, specimens may be microwaved in batches or a single storage case may be treated with a chemical fumigant such as Whitmire's #110 Synthetic Pyrethrin (Southern Mill Creek Company, P.O. Box 1096, Tampa, Florida 33601). Whitmire's #110 has a quick "knockdown" with no residual effect. The treatment should be repeated once a week for four weeks for maximum effect. A soon-to-be-released insecticide,

A solution of the starting point problem in the nomenclature of fungi

Abstract: Summary The present system of disparate starting points for fungi is shown to be incapable of producing a stable unambiguous nomenclature. Its faithful application not only imposes an intolerable sterile bibliographic burden on taxonomists but also forces them to make subjective biological decisions. A solution to this problem exists in Prop. 32 for modification of the International Code of Botanical Nomenclature. This proposal would give a single starting point date of 1753 for all fungi but would retain the protected status granted by the existing Art. 13.I.f to names used by Fries in his Systema vol. 2 and 3 extend it to vol. 1 and to Persoon's Synopsis for the names for which this was the starting point book. The advantages for nomenclatural stability and simplicity of this proposal are outlined, and contrasted with the catastrophic changes that would arise from adoption of the current Prop. 31 (which we therefore strongly oppose).

Geographic races of conocephalum (marchantiales) as defined by flavonoid chemistry

Abstract: An earlier proposal that Conocephalum conicum may exist as a group of geographic races is supported by a more extensive survey of the flavonoid glycosides isolated from samples across its Northern Hemisphere distribution. European, North American, and Asian samples are clearly distinguished, and sub-groups may be recognised within these broad subdivisions. The local Sino-Japanese species C. supradecompositum is clearly distinguished on the basis of flavonoid glycosides from C. conicum.

Silene pratensis (rafn) godron & gren., the correct name for white campion or white cockle (silene alba (miller) e. h. l. krause, nom. illeg.)

Abstract: Summary Silene alba Muhl. ex Britton (1893), although considered to be an illegitimate substitution for S. nivea (Nutt.) Otth, is validly published and as a result S. alba (Miller) E. H. L. Krause (1901), the widely used name for the weed white campion or white cockle, is illegitimate. It is shown that the correct name for this species in Silene is S. pratensis (Rafn) Godron & Gren. A new taxonomic treatment of the infraspecific variation within S. pratensis is outlined and three new subspecific combinations proposed.