摘要:

SummaryA considerable number of instances are discussed where parallel developments outside family relationships occur, restricted in geographical distribution:1)divaricate shrubs in New Zealand, with 51 species in 23 families,2)the Eucalypt leaf type in Australia, occurring in 12 families,3)terete and holly‐type leaves in Western Australia,4)red autumn leaf coloration in Northeastern America and Japan,5)leaf convergence in Mediterranean climates,6)the cushion plants in Southern Patagonia,7)parallels in anatomical structure in the Southwestern United States,8)red tubular hummingbird flowers of the Southwestern United States.This is contrasted with cases of convergent characters on the genus or family level, or geographically unrelated parallel development. In the discussion it is argued that such parallel development might well represent rare‐nonsexual transfer of chromosomal segments. It is obviously one of the major evolutionary mechanisms in the development of the multitude of dicotyledonous species.

ISSN:0040-0262    

DOI:10.2307/1218877

出版商:Wiley    

年代:2019

数据来源: WILEY

摘要:

SummaryThe use of vegetation in interpreting geological phenomena is becoming an important tool in the search for ore deposits that are buried under thick soil cover or layers of unmineralized rock. Species assemblages and plant density are useful in mapping geologic strata of different chemical composition and reservoir capacity. Hidden ore deposits can be located through chemical analysis of plant tissue, by mapping the distribution of species, and by observing toxic effects caused by an excess of metals as well as signs of faulty nutrition or deranged metabolism in plants whose roots are in contact with ore.Plant indicators of ore deposits may be species that are adapted to living exclusively on rocks or soils that supply unusual amounts of a particular element, or they may be species of wide distribution that favor mineralized ground under certain local conditions because of a change in acidity or availability of major plant constituents. Plants that are not highly tolerant of metals in an ore assemblage may exhibit toxicity symptoms or be completely absent over ore.Geobotanical techniques of mapping indicator plant species and communities, combined with observation of changes in plant appearance can aid the geologist in prospecting for hidden ore deposits.

ISSN:0040-0262    

DOI:10.2307/1218878

出版商:Wiley    

年代:2019

数据来源: WILEY

摘要:

SummaryIn this paper I argue in favor of the use of the “biological” species concept rather than either a “typological” concept or a “morphological” concept. In simple form my argument is as follows: Biologists are not merely interested in storing data but in finding satisfactory explanations for that data. Taxonomy is an integral part of this theoretical enterprise. The most satisfactory theory at present for understanding (providing explanations for) biological phenomena is the synthetic theory of evolution. Development of this theory requires use of the biological species concept rather than the other species concepts. The basic limitation on the use of this concept is noted and some objections to the use of the concept are considered.

ISSN:0040-0262    

DOI:10.2307/1218879

出版商:Wiley    

年代:2019

数据来源: WILEY

摘要:

SummaryCurrent methods of specimen identification are surveyed, and algorithms are given for constructing dichotomous keys and for identifying specimens directly with a polythetic polyclave procedure. Although usable without computers, these techniques have been automated as Fortran programs on a time‐sharing system. Taxon/character data are encoded as a hierarchy of data matrices for use with the various programs. Large‐scale taxonomic information systems are also briefly discussed.

ISSN:0040-0262    

DOI:10.2307/1218880

出版商:Wiley    

年代:2019

数据来源: WILEY

摘要:

SummaryA new course covering major aspects of the use of computers in systematics was recently offered at Michigan State University. The course consisted of lectures delivered by 12 speakers, discussion sessions, and reports on student projects. Topics included computers and systematics, the Flora North America Program, specimen identification and key‐construction by computer, parallels between specimen identification and medical diagnosis, plant disease diagnosis by computer, information problems in paleontology, distribution mapping by computer, biometrics and statistical studies with computers, probabilistic approaches to specimen identification, computers as aids to teaching systematic biology, numerical taxonomy, the modeling of genetic and evolutionary systems, possible computerized nomenclatural aids, and biogeographical analysis with computers.

ISSN:0040-0262    

DOI:10.2307/1218881

出版商:Wiley    

年代:2019

数据来源: WILEY

摘要:

SummaryKnown chromosome numbers in the Loranthaceae are reviewed and 102 new records added. The basic number of the family is x = 12 and there has been progressive aneuploid reduction to x = 8. The early development of the family has been under temperate conditions in the Southern Hemisphere, where stocks with x = 12 and 11 became established in temperate South America and Australasia. Rapid aneuploid reduction continued after the establishment of strong continental isolation, establishing numbers of x = 9 and 8 in the Old and New Worlds respectively. Massive secondary radiation in the tropics has followed, involving the 12‐, 9‐ and 8‐paired stocks.Increase in chromosome size occurred during the tropical radiation, perhaps compensating for loss of recombination potential due to aneuploid reduction. Polyploidy is a rare and recent phenomenon in the history of the family, being documented in only two Central American taxa. One of these may be an autoploid.

ISSN:0040-0262    

DOI:10.2307/1218882

出版商:Wiley    

年代:2019

数据来源: WILEY

摘要:

SummaryKnown chromosome numbers in the Viscaceae and Eremolepidaceae are reviewed and 73 new records added. No basic number is presently evident for either family as a whole. In the Vicaceae two fundamental chromosome groups are apparent. The first is characterized by x = 14 and is itself composed of two subgroups, one with large chromosomes (Dendrophthora‐Phoradendron), and the other with medium sized chromosomes (Arceuthobium‐Korthalsella). The second chromosome group is composed ofViscumand its close relatives which possess numbers of x = 10, 11, 12, and 13 and which have large chromosomes.In the x = 14 group, theDendrophthora‐Phoradendronalliance is strictly New World. TheArceuthobium‐Korthalsellaalliance, however, has both Old and New World representation.Arceuthobiumis present in both the Old and New Worlds andKorthalsellahas an Old World and Pacific distribution. TheViscumalliance is strictly Old World.Some infra‐generic aneuploidy is known inViscumandDendrophthora. Polyploidy is apparently rare, known only inPhoradendronfrom the Galápagos Islands and inViscumfrom New Guinea and northern Australia.A northern origin is postulated for the Viscaceae, with subsequent widespread radiation into the tropics of both the New and Old Worlds.The Eremolepidaceae, a group of three New World genera, does not appear to be karyologically related to other mistletoe families; it is postulated they may be aerial parasites in the Santalaceae, which is primarily a family of terrestrial root parasites.

ISSN:0040-0262    

DOI:10.2307/1218883

出版商:Wiley    

年代:2019

数据来源: WILEY

ISSN:0040-0262    

DOI:10.2307/1218884

出版商:Wiley    

年代:2019

数据来源: WILEY

摘要:

SummaryOf 762 new species described by Ducke ten belong to the generaThiloa, RamatuellaandBuchenavia(Combretaceae). They were described in two series of articles, containing respectively ten and six papers. Type specimens should be located in MG and RB respectively, but only one of the six species described in the first series is in fact represented in MG by a type specimen. Type specimens of all four species described in the second series of papers are, on the other hand, present at RB. Details of the locations of all type specimens are provided, and possible reasons for the non‐existence of types at MG discussed.

ISSN:0040-0262    

DOI:10.2307/1218885

出版商:Wiley    

年代:2019

数据来源: WILEY

摘要:

SummaryCharles Gaudichaud‐Beaupré described the genusCharpentierain the form of two species,C. ovataandC. obovata, but did not indicate which of the species should serve as type. Horace Mann was the first to indicate the lectotype of the genus when he reducedC. obovatato synonymy. The reference to the lectotype in theIndex Nominum Genericorumshould therefore be Mann, Proc. Amer. Acad. Arts 7: 200. 1866, rather than Schinz (in Engler et Prantl,Nat. Pflanzenfamilien3 (1.a): 101 Aug. 1893) as it is at present.

ISSN:0040-0262    

DOI:10.2307/1218886

出版商:Wiley    

年代:2019

数据来源: WILEY