摘要:

SummaryUsing the newly‐completed second edition of the first volume of Flora Europaea as a starting‐point, the author, a member (until 1993) of the Flora Europaea Editorial Committee, reviews the aims and scope of the whole project, and considers what influence it has had on European vascular plant taxonomy in the post‐war period. The prospects of completing the second edition are discussed, and finally some comment is made on the present difficulties for taxon

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1995.tb01194.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1995.tb01195.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryThere are three general mechanisms by which phenotypic benefits are transferred between unrelated organisms. First, one organism maypurloinbenefits from another by preying on or parasitizing the other organism. Second, one organism may enjoy benefits that areincidentalto or aby‐productof the self‐serving traits of another organism. Third, an organism mayinvestin another organism if that investment produces return benefits which outweigh the cost of the investment. Interactions in which both parties gain a net benefit are mutualistic. The three mechanisms by which benefits are transferred between organisms can be combined in pairs to produce six possible kinds of original or ‘basal’ mutualisms that can arise from an amutualistic state. A review of the literature suggests that most or all interspecific mutualism have origins in three of the six possible kinds of basal mutualism. Each of these three basal mutualisms have byproduct benefits flowing in at least one direction. The transfer of by‐product benefits and investment are common to both intra‐ and interspecific mutualisms, so that some interspecific mutualisms have intraspecific analogs. A basal mutualism may evolve to the point where each party invests in the other, sometimes obscuring the nature of the original interaction along the way. Two prominent models for the evolution of mutualism do not include by‐product benefits: Roughgarden's model for the evolution of the damsel‐fish anemone mutualism and the ‘Tit‐for‐Tat’ model of reciprocity. Using the conceptual framework presented here, including in particular by‐product benefits, I have shown how it is possible to construct more parsimonious al

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1995.tb01196.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryThe interrelationships within the clade comprised of turtles, pareiasaurs, and procolophonid‐like taxa are investigated via a cladistic analysis incorporating 56 characters. A single most parsimonious tree was found (80 steps, c. i. = 0·8) in which the successive outgroups to turtles are: pareiasaurs,Sclerosaurus, lanthanosuchids, procolophonoids (=Owenetta, Barasaurusand procolophonids), and nyctiphruretians (= nycteroleterids). Thus, as suggested recently by other workers (Reisz, in Fischman, 1993) turtles are the highly modified survivors of a radiation of poorly‐known reptiles commonly called ‘parareptiles’. Pareiasaurs are united with turtles on the basis of twenty unambiguous derived features which are absent in other basal amniotes (=‘primitive reptiles’) and reptiliomorph amphibians: for example, the medially located choana, enlarged foramina palatinum posterius, blunt cultriform process, fully ossified medial wall of the prootic, opisthotic‐squamosal suture, lateral flange of exoccipital, loss of ventral cranial fissure, thickened braincase floor, ‘pleurosphenoid’ ossification, reduced presacral count, acromion process, trochanter major, reduced fifth pedal digit, and presence of transverse processes on most caudals. Recent phylogenetic proposals linking turtles with captorhinids, with dicynodonts, and with procolophonoids are evaluated. None of the proposed traits supporting the first two hypotheses is compelling. The procolophonoid hypotheses is supported by only one synapomorphy (the slender stapes). All other synapomorphies proposed in favour of the above groupings either occur in many other primitive amniotes, or are not primitive for turtles, or are not primitive for the proposed chelonian sister‐group.NyctiphruretusandLanthanosuchids and nycteroleterids, often considered to be seymouriamorph amphibians, are demonstrated unequivocally to be amniotes. The ‘rhipaeosaurs’, currently considered to be pareiasaur relatives, are shown to be a heterogenous assemblage of seymouriamorphs, therapsids and nycteroleterids.The phylogeny proposed here indicates that many of the traits of the earliest known turtle,Proganochelys, previously interpreted as unique specialisations, also occur in pareiasaurs and other near outgroups of turtles, and must instead represent the primitive chelonian condition: for example, the wide parietals and the short quadrate flange of the pterygoid. The sequence of acquisition of chelonian traits is discussed: many features once thought to be diagnostic of turtles actually characterize larger groupings of procolophonomorphs, and must have evolved long before the chelonian shell appeared. These traits include most of the chelonian‐pareiasaur synapomorphies listed above, and many others which characterize more inclusive groupings found in this analysis. In puttingProganochelysmuch closer to the main line of chelonian evolution, in elucidating the sequence of acquisition of chelonian traits, and in reducing greatly the number of differences between turtles and their nearest relatives, this study helps bridge one of the major gaps in the fossil record.The failure of previous cladistic analyses to identify correctly the nearest relatives of turtles is attributed to biased character selection, caused by an over‐reliance on cranial characters deemed ‘important’ by earlier workers, and by a tendency to shoehorn ‘parareptile’ taxa into phylogenies derived from analyses restricted to ‘mainstream’ groups such as synapsids, diapsids, turtles, and ‘captorhinomorphs’. Many of the synapomorphies that resolve turtle origins are postcranial, and the three nearest outgroups to turtles are all highly bizarre groups which were dismissed as ‘too specialized’ by early workers and continued to be inadequately asse

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1995.tb01197.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY