Showing papers in "Taxon in 1997"

On the evolutionary origins of the cacti

Abstract: Understanding evolutionary responses of plants to desert environments depends upon phylogenetic knowledge of desert plants. The diverse American desert family Cactaceae has been presumed, on the basis of distinctiveness, to be phylogenetically isolated and relatively ancient (> 65 million years old). Using maximum likelihood and parsimony analyses of the rapidly evolving internal transcribed spacer (ITS) sequences of nuclear ribosomal DNA (nrDNA), we show that the cacti are phylogenetically nested among other aridity-adapted lineages of the angiosperm family Portulacaceae. The ITS divergence between pereskioid cacti and the genus Talinum (Portulacaceae) is less than that between many Portulacaceae genera. Synthesis of the ITS data with morphological and chloroplast DNA evidence suggests an origin of cacti in mid-Tertiary, c. 30 million years ago, and a later Tertiary diversification coincident with development of the American desert. This, in turn, implies that the diversification rate in cacti was much higher than in their nearest relatives. The present results illustrate the central role of phylogenetic reconstruction in ecological and evolutionary theory.

Typification of Linnaean specific and varietal names in the Leguminosae (Fabaceae)

Abstract: The Linnaean Plant Name Typification Project at the Natural History Museum, London, has been concentrating its efforts on Linnaean plant names that lack formally designated types. Family by family, the Project has been collaborating with specialists worldwide in order to establish choices of type that support the current usage of the names concerned. For the present paper, names now placed in the Leguminosae were investigated. Out of a total of almost 9000 Linnaean plant names at the rank of species or variety, 747 now fall within this family (counting homotypic Linnaean names as separate units, but excluding 12 renamings and recombinations, by Linnaeus, of other authors' names), which represents an important subset of the whole. Of these 747, 430 have already been effectively typified, leaving 317 unresolved. The present paper is one of a series intended to publish new typifications resulting from the Project's collaborative research. Subsequent papers, soon to follow, will typify names in the families Compositae (Asteraceae), Labiatae (Lamiaceae), and Gramineae (Poaceae). These works will pave the way towards the Project's main publication, a comprehensive catalogue of Linnaean plant names and their types.

Taxonomy versus cladonomy, a fundamental controversy in biological systematics

Abstract: In an article in the February issue of this journal, Welzen (1997) has expressed clearly his reservations about my paper 'In defence of paraphyletic taxa' (Brummitt, 1996a) which was originally read at an AETFAT (Association pour l'Etude Taxonomique de la Flore d'Afrique Tropicale) Congress in 1994. In the same issue of this journal, however, Sosef (1997) has come to very much the same conclusions as I had, emphasizing the inevitability of paraphyletic taxa. Essentially the same conflict of views was addressed in a formal debate at the Linnean Society of London on 6 March 1997, when a motion "that this house believes that Linnaean classification without paraphyletic taxa is nonsensical" was proposed by myself and seconded by my colleague Alan Paton. The motion was approved by 69 votes to 43. While this vote itself proves nothing, it does apparently indicate that there is a significant body of opinion in the systematic community (in the U.K. at least) which does not accept the view widely promoted today among followers of 'phylogenetic systematics' that paraphyletic taxa should have no place in biological classification. This is indeed now a matter of major controversy in systematics, and it is timely to review the arguments and further prospects.

Hierarchical models, reticulate evolution and the inevitability of paraphyletic supraspecific taxa

Abstract: A phylogenetic tree can be subdivided according to a monophyletic hierarchical model, in which only monophyletic units figure, or according to a "Linnaean" hierarchical model in which both monoand paraphyletic units occur. Most present-day phylogeneticists try to fit the monophyletic model within the set of nomenclatural conventions that fit the Linnaean model. However, the two models are intrinsically incongruent. The monophyletic model requires a system of classification of its own, at variance with currently accepted conventions. Since, however, the monophyletic model is unable to cope with reticulate evolutionary relationships, it is unsuited for the classification of nature. The Linnaean model is to be preferred. This renders the acceptance of paraphyletic supraspecific taxa inevitable.

A classification of and key to the supraspecific taxa in Eleocharis (Cyperaceae)

Abstract: A comparison of former supraspecific classifications is made and a new, revised system is proposed for Eleocharis (Cyperaceae). Four subgenera, seven sections, eight series, and seven subseries are recognized. A key to subgenera and sections is included along with type citations, synonymies, and representative species. Two new series, E. ser. Albidae and ser. Rostellatae, are described, along with one new combination, E. sect. Baeothryon, and two transfers in rank, E. subser. Acutae and E. subser. Sulcatae.

A taxonomic information model for botanical databases: the IOPI Model

Abstract: Summary Berendsohn, W. G.: A taxonomic information model for botanical databases: the IOPI Model. ϑ Taxon 46: 283-309. 1997. ϑ ISSN 0040-0262. A comprehensive information model for the recording of taxonomic data from literature and other sources is presented, which was devised for the Global Plant Checklist database project of the International Organisation of Plant Information (IOPI). The model is based on an approach using hierarchical decomposition of data areas into atomic data elements and ϑ in parallel ϑ abstraction into an entity relationship model. It encompasses taxa of all ranks, nothotaxa and hybrid formulae, "unnamed taxa", cultivars, full synonymy, misapplied names, basionyms, nomenclatural data, and differing taxonomic concepts (potential taxa) as well as alternative taxonomies to any extent desired. The model was developed together with related models using a CASE (Computer Aided Software Engineering) tool. It can help designers of biological information systems to avoid the widely made error of over-simplification of taxonomic data and the resulting loss in data accuracy and quality.

A nomenclatural checklist of supraspecific names in Taraxacum

Abstract: Summary legitimacy are determined, all valid names are given types, and type specimens are selected and quoted where available. Comments are confined to the nomenclatural status of the names; for important taxonomic synonyms the accepted names are given, and names considered correct are highlighted.

Decay analysis of large sets of phylogenetic data

Abstract: Summary matrix was constructed so that all trees up to five steps longer than the shortest could be saved and examined. A series of decay analyses was then conducted with this data set to determine the effects produced in the results when all trees are not found and to evaluate methods that could be used to conduct decay analyses of large data sets. Limiting the number of trees to be saved resulted in overestimates of support for monophyletic groups, a problem that became substantial when only 33 % of all trees were examined. Two methods of decay analysis that use constraint

Sarcobataceae - a new family of Caryophyllales.

Abstract: A review of the discovery and early descriptions of Sarcobatus as well as of its taxonomic history is presented Studies of the form and size of sieve-element plastids in the order Caryophyllales reveal significant differences between Sarcobatus (so far in Chenopodiaceae) and the majority of the Chenopodiaceae/Amaranthaceae clade (ie, suborder Chenopodiineae) The presence of P3cfform sieve-element plastids and concomitant absence of chenopod-specific P3f-form plastids reinforce other evidence, in particular from chloroplast DNA sequencing, to make appear Sarcobatus quite distinct from the Chenopodiineae clade and suggest that its proper place is in the vicinity of the Phytolaccaceae and Nyctaginaceae Therefore, Sarcobatus is segregated as a new family, Sarcobataceae

A tribal classification of the Periplocoideae (Apocynaceae)

Abstract: The diagnostic features used to delimit genera are enumerated and critically analysed. Floral characteristics are important: shape and depth of the corolla tube, and positions of outer corona, stamens, and gynostegium. Coronal structure is valuable but can be misleading. Vegetative features are sometimes consistent within genera and may serve as a complement to floral characteristics. The Periplocoideae are, for the first time, subdivided: three tribes are recognized, two of them newly described and named, and the individual genera and generic synonyms are mentioned for each. Some nomenclatural new combinations, required as a consequence of newly proposed synonyms, are validated in the genera Camptocarpus (4), Cryptolepis (4), Decalepis (2), and Pentopetia (2).

Familial Placement of Cyrtandromoea , Titanotrichum and Sanango : Three Problematic Genera of the Lamiales

Abstract: Summary gieae, the monogeneric Titanotricheae are perhaps sister to the remainder of the Cyrtandroideae, and Sanango is placed in the Gesnerieae as was predicted by recent morphological and chemical analyses.

The anther : form, function, and phylogeny

Abstract: Preface 1. About anthers and stamens and what they do 2. The fossil history of stamens 3. The origin and early evolution of angiosperm stamens 4. Diversity and evolutionary trends in angiosperm anthers 5. Are stamens and carpels homologous? 6. Temporal control points in anther differentiation: implications for anther evolution 7. Diversity of endothecial patterns in the angiosperms 8. The oxalate package or so-called resorption tissue in some bee-pollinated angiosperms 9. Anther adaptations for animal pollination 10. Anther differentiation in the Asclepiadaceae: form and function 11. Stamen development in legumes with emphasis on porate stamens of Cassieae 12. Anther investigations: a review of methods 13. A bibliography of stamen morphology and anatomy Index.

A contribution to the generic delimitation of Sechium (Cucurbitaceae, Sicyinae)

Abstract: The generic limits of Sechium continue to be controversial. A phenetic analysis of the species of Sechium and its allies in subtribe Sicyinae, using both palynological and macromorphological characters, was carried out. The results of the analysis basically support the taxonomic circumscription of this genus proposed by Jeffrey (1978). Both cluster and ordination analyses showed that all the species recognized by Jeffrey as pertaining to the genus Sechium, as well as others more recently described, form a well defined group constituted by 11 species and clearly separated from other taxa in the subtribe Sicyinae. The observed clustering within Sechium does not correspond to the two sections of the genus recognized by Jeffrey. Sechiopsis appears to be the closest relative of Sechium.

Pollen morphology and the systematic position of Triplostegia (Dipsacales)

Abstract: Triplostegia comprises two species of perennial herbs from southeast Asia, T. glandulifera and T. grandiflora. The systematic position of the genus has been debated ever since it was described, and ...

(1291-1292) Proposals to Conserve the Names Myrica and Gale (Myricaceae) with Conserved Types

Abstract: Linnaeus included five species in his genus Myrica. M gale, cerifera, aspleniifolia (as 'asplenifolia'), quercifolia, and cordifolia, and he himself emphasized the differences between M gale and M cerifera (Gen. PI., ed. 5: 449. 1754). M aspleniifolia was early made the type of the genus Comptonia L'Her. ex Ait. 1789. Spach (Hist. Nat. Veg. 11: 256-266. 1841) split the Linnean genus into three, adopting the names Gale Tourn. ex Duhamel, Myrica, and Comptonia. He was followed by Chevalier who prepared a monograph of the family as his doctorate thesis in Mem. Soc. Sci. Nat. Cherbourg 32: 85-341. 1901), giving good reasons for recognizing three distinct genera, Gale (with few species), Comptonia (with one species) and Myrica (with many species), the latter divided into three sections: M sect. Morella (Lour.) A. Chev., sect. Faya (Webb & Berthel.) C. DC., and sect. Cerophora (Raf.) A. Chev. Both Spach and Chevalier placed M gale in Gale, not Myrica, but neither cited types for any of the names mentioned. Hutchinson (in Oliver, Fl. Trop. Afr. 6(2): 307-314. 1917) whilst stating "it is not disputed that there are good reasons for their segregation" considered it best for the purposes of the flora to consider the segregates as infrageneric taxa, following Engler & Prantl (Nat. Pflanzenfam. 3(1): 27-28. 1888, as subgenera). He maintained this position later (Hutchinson, Gen. Fl. P1. 2: 121. 1967). Recent work on the family, e.g. on chromosomes and essential oils, as summarized by MacDonald (in Crane & Blackmore, Evol. Hamamelidae 2: 147-165. 1989) indicates generic status is undoubtedly necessary, as Spach and Chevalier had made clear. No one, however, who has agreed to the necessity has dealt with the nomenclatural problems involved. In fact White (in Opera Bot. 121: 173-188. 1993), after explaining Chevalier's view, stated "The three entities can be keyed out but their differences are relatively slight, and to segregate them detracts from the striking uniformity of the group, besides creating many nomenclatural problems". The differences are, however, considerable and the time has come to take decisions. Myrica gale has been chosen as type of Myrica on at least five occasions (see Steam, Sp. P1. Facs., App.: 133. 1959). Only Hylander (in Uppsala Univ. Arsskr. 7: 40. 1945) and Rehder (Bibl. Cult. Trees: 87. 1949) have dissented and chosen M. cerifera, specifically refuting the previous choice. They clearly felt that segregated genera would ultimately be accepted and understood the consequences. We are of course well aware of the importance of Myrica gale in north temperate ecology. Hundreds of ecological papers must mention the species; there are fourteen references alone in that seminal work by Tansley (Brit. Isl. Veg. 1939). Strong opposition to the proposal may be expected from palaearctic botanists. Nevertheless, despite White's (l.c.) attempts to decimate the African species, the tropical and

Announcing a Test and Trial Phase for the Registration of New Plant Names (1998-1999)

Abstract: Registration of nomenclatural novelties seems to me a natural way to go, heading into the 21st Century. It will enable us to find quickly what new names have been published, and to be sure that we have not missed any new name hidden in the paper mountain of botanical literature that comes out each year around the globe. This is particularly important for one-off publications (floras, field guides, etc.), which are notorious for 'hiding' new names. Some people seem to think that registration implies censorship, but this is wrong. As in the current Index kewensis all names will be listed, and without comment as to status, and as soon as received at one of the registration centres. My only caution to those looking at the mechanisms for making registration effective is that they should ensure there is a large network of registration centres or offices spread evenly around the world. This is necessary to make it easy to submit novelties for registration, given the apparently worsening state of mail services in all areas.

Notes on Dictyota vieillardii and D. adnata (Dictyotaceae, Phaeophyta)

Abstract: Summary Results Dictyota vieillardii Ktitz. (1863: 14) was described from a specimen collected by Vieillard in New Caledonia in 1861. Ktitzing's description is of a small, dark, intri- cate plant with irregularly divided straps and linear segments. Branching was said to be alternately pinnate, with patent, distant, spinescent pinnae.

Types of names in Ampelocissus and Cissus (Vitaceae) referring to taxa in the Caribbean, Central and N. America

Abstract: Generic boundaries in the Vitaceae are ill defined, being based on characteristics of, e.g., the inflorescence, the development of a nectariferous disc and its adnation to the ovary wall. The number of genera increased from two (Linnaeus, 1753) through ten (Planchon, 1887; Suessenguth, 1953), to 13-15 genera (Mabberley, 1987; Gunn & al., 1992; Greuter & al., 1993). The two major New World genera of Vitaceae are Cissus L., centred on S. America, and Vitis L., most diverse in N. America (Moore, 1991; Planchon, 1887). The remaining genera of the family have the largest number of their native species in other continents, such as Africa (Ampelocissus Planch.) and Asia (Ampelopsis Michx. and Parthenocissus Planch.; Planchon, 1887). Most N. American species of Vitaceae belong to Ampelopsis, Parthenocissus, and Vitis, whereas all four New World Ampelocissus species are found in Central America and the Caribbean.