Phyletic Relationships of Living Sharks and Rays

A set of hypotheses are developed for the origin of living sharksand rays and the interrelationships of their major groups, usingsome methods of cladistic analysis to relate groups with sharedderived characters. Comparative studies on living sharks andrays combined with new data on fossil sharks suggests that theliving groups ultimately stem from a common ancestral groupof "neoselachian" sharks with many modern characters. Reinterpretationsof "amphistyly" in modern sharks is presented on new data.     

An even "newer" animal phylogeny

Metazoa are one of the great monophyletic groups of organisms. They comprise several major groups of organisms readily recognizable based on their anatomy. These major groups include the Bilateria (animals with bilateral symmetry), Cnidaria (jellyfish, corals and other closely related animals), Porifera (sponges), Ctenophores (comb jellies) and a phylum currently made up of a single species, the Placozoa. Attempts to systematize the relationships of these major groups as well as to determine relationships within the groups have been made for nearly two centuries. Many of the attempts have led to frustration, because of a lack of resolution between and within groups. Other attempts have led to "a new animal phylogeny". Now, a study by Dunn et al., using the expresssed sequence tag (EST) approach to obtaining high-throughput large phylogenetic matrices, presents an "even newer" animal phylogeny. There are two major aspects of this study that should be of interest to the general biological community. First, the methods used by the authors to generate their phylogenetic hypotheses call for close examination. Second, the relationships of animal taxa in their resultant trees also prompt further discussion.     

Foreigners or multicultural citizens? Press media's construction of immigrants in South Korea

This paper examines the ways in which new immigrants to South Korea are portrayed and constructed in press media. The influx of labour and marriage migrants from Southeast Asia and China to South Korea since the early 1990s has been significant enough to cause national concerns about diversity and the country's future as a multiethnic society. Mainstream newspapers in South Korea have been a major shaper of the public opinion of diverse groups of immigrants whose presence is becoming increasingly visible in this country with a strong self-image as a mono-ethnic nation. The ways in which these new immigrants, typically lower class, are constructed in public discourses expose the nexus of citizenship, class and ethnicity. Using articles from two major South Korean newspapers between 1990 and 2008 as data, the analysis highlights the economic and historical contexts in which public discourses on new immigrants have been formed and transformed.     

A comparison of the colonization of the planktic realm and the land

Metazoans evolved in the sea and quickly invaded benthic niches. It was from these niches that other large ecosystems were colonized through the later Precambrian and the Phanerozoic. Entering these new environments, the colonists encountered new sets of macroevolutionary controls. Narratives of each colonization are important for historical ecology, while comparison of different events can throw light on these underlying controls. Recent narrative work on the evolution of plankton has suggested that this series of events was unique in respect of its duration and method. Animals have been migrating into the plankton since the Proterozoic, and all the main planktic groups have a benthic origin. Migration was usually by single species acting independently of their native community. A comparison with the other major Phanerozoic colonization, that of the land, highlights these unusual features. Colonization of the land began in the Ordovician and seems to have occurred sporadically. Several of the major groups of terrestrial animals originated on land. The invasion of land is usually related to the evolution of land plants and is perhaps best regarded as migration at the level of the community. The major differences between the two colonizations may be attributable to the dominant control of the environment over plankton versus that of biotic interaction over land animals.     

Nachtrag zu ‘Hepaticae Bomeenses (Oxford University Expedition to Sarawak, 1932)’

Abstract

Recent empirical advances in bryophyte systematics have been made in the discovery and detailed study of new characters. However, theoretical considerations have not kept pace. Proper attention has not been paid to how these new characters can be used to discover relationships among groups and produce classifications. Recent cladistic studies of the relationships of the major groups of bryophytes have demonstrated the feasibility and usefulness of an approach to phylogenetic systematics derived from the works of Hennig. A Hennigian approach attempts to find the particular hierarchical level at which a given character is a homology (i.e. a synapomorphy or shared, derived character), relationships are established by searching for congruent patterns of homologies, and the resulting hierarchical scheme is used as the basis for a classification. Such an approach provides a rigorous and explicit logic for investigating phylogeny and recognizing natural, historically discrete taxa. The theoretical advantages of a Hennigian approach are discussed and illustrated by examining the congruence of new characters data with preliminary cladograms of the major bryophyte groups.     

Host shifts and evolutionary radiations of butterflies

Ehrlich and Raven proposed a model of coevolution where major host plant shifts of butterflies facilitate a burst of diversification driven by their arrival to a new adaptive zone. One prediction of this model is that reconstructions of historical diversification of butterflies should indicate an increase in diversification rate following major host shifts. Using reconstructed histories of 15 butterfly groups, I tested this prediction and found general agreement with Ehrlich and Raven''s model. Butterfly lineages with an inferred major historical host shift showed evidence of diversification rate variation, with a significant acceleration following the host shift. Lineages without an inferred major host shift generally agreed with a constant-rate model of diversification. These results are consistent with the view that host plant associations have played a profound role in the evolutionary history of butterflies, and show that major shifts to chemically distinct plant groups leave a historical footprint that remains detectable today.     

A phylogenetic study of krill (Crustacea: Euphausiacea) reveals new taxa and co-evolution of morphological characters

The first comprehensive phylogenetic study of Euphausiacea (all 86 valid species) is presented. It is based on four molecular markers and 168 morphological characters (including 58 characters of the petasma). Phylogenetic analyses support the monophyly and robustness of the families Bentheuphausidae and Euphausiidae and reveal three major clades for which we erect three new subfamilies: Thysanopodinae, Euphausiinae and Nematoscelinae. All genus-level clades are statistically supported (except Thysanopoda in molecular analyses), deeply nested within the subfamily-level clades, and encompass 14 new species groups. Copulatory structures have a major impact on tree topology in the morphological analysis, the removal of which resulted in only half the number of supported clades and genera. We revealed three groups of morphological characters, which are probably coupled with the same biological role and thus interlinked evolutionarily: (i) antennular peduncle and petasma (copulation); (ii) eyes and anterior thoracopods (feeding); and (iii) shape of carapace and pleon (defence). We analysed the evolutionary pathways of the clades into main oceanic biotopes and compared them with morphological adaptations most likely to be coupled with this process.     

12S,19- and 12S,20-dihydroxyeicosanoids: novel 12S-hydroxy-5,8-cis-10-trans-14-cis-eicosatetraenoic acid metabolites formed by hydroxylation and reduction in murine lymphocytes

Murine spleen cells and purified B lymphocytes oxidized arachidonic acid via the lipoxygenase pathway. The major metabolite of both the whole spleen and enriched B lymphocytes was 12S-hydroxy-5,8-cis-10-trans-14-cis-eicosatetraenoic acid. A novel metabolite was observed that did not have an absorbance from 210 to 400 nm, indicating the absence of a conjugated double bond system. The new metabolite was converted to the methyl ester, reduced by platinum oxide, derivatized to the trimethylsilyl ether, and analyzed by gas chromatography-mass spectrometry. A major and a minor component were observed in the analysis of the new compound. The major component had major diagnostic ions indicating the presence of hydroxyl groups at C-12 and C-19. The minor component had major diagnostic ions indicating the presence of hydroxyl groups at C-12 and C-20. The new metabolites are characterized as a mixture of 12S,19- and 12S,20-dihydroxyeicosanoids presumably formed by hydroxylation and reduction of one or more double bonds of 12S-hydroxy-5,8-cis-10-trans-14-cis-eicosatetraenoic acid. These metabolites were formed predominantly with whole spleen lymphocytes but could be detected at longer incubation times or by using 12S-hydroxy-5,8-cis-10-trans-14-cis-eicosatetraenoic acid as the starting substrate with highly enriched B lymphocytes.     

中国现代石松类和蕨类的系统发育与分类系统

石松类和蕨类植物是以孢子繁殖的维管植物,在陆地植物演化上占据重要地位。随着分子系统学研究的开展,各大类群间的系统发育关系得以阐明,传统上的概念得以修正,新的现代石松类和蕨类植物的分类系统也被提出,并不断得到完善。该文介绍国内外在蕨类植物系统发育方面的研究成果,重点讨论中国分布的类群的分类处理。文中提出了一个完整的中国现代石松类和蕨类植物的分类系统,包括5亚纲、14目、39科及12亚科、约140余属。     

ALTERNATION OF GENERATIONS IN LAND PLANTS: NEW PHYLOGENETIC AND PALAEOBOTANICAL EVIDENCE

Current ideas on the evolution of alternation of generations in land plants are reviewed in the context of important recent advances in plant systematics and the discovery of remarkable new palaeobotanical evidence on early embryophyte life cycles. An overview of relationships in major groups of green plants is presented together with a brief review of the early fossil record as a prelude to discussing hypotheses of life cycle evolution. Recent discoveries of life cycles in the early fossil record are described and assessed. The newly discovered gametophyte and sporophyte associations are based on exceptionally well-preserved material from the Rhynie Chert, Scotland (Middle Devonian: 380–408 Myr) and compression fossils from other Devonian localities. These data document diplobiontic life cycles in plants at the ‘protracheophyte’ and early tracheophyte level of organization. Furthermore, the early fossils have a more or less isomorphic alternation of generations, a striking departure from life cycles in extant embryophytes. This unexpected similarity between gametophyte and sporophyte calls for a cautious approach in identifying ploidy level in early groups. Viewed in a systematic context, the neontological and palaeontological data contribute towards the formulation of a coherent hypothesis of life cycle evolution in major, early embryophyte groups. Evidence from extant groups strongly supports a single direct origin of the diplobiontic life cycles of land plants from haploid, haplobiontic life cycles in ancestral ‘charophycean algae’. The interest of the new palaeobotanical data lies in its relevance to life cycle evolution at the restricted level of vascular plants rather than at the more general level of embryophytes (vascular plants plus ‘bryophytes’). The occurrence of morphologically complex, axial gametophytes in early vascular plants is consistent with the moss sister-group proposed in some cladistic analyses. Similarities of moss gametophytes to fossils in the vascular plant stem-group are discussed, and it is argued that the late appearance of mosses in the macrofossil record may be due to the problem of recognizing stem-group taxa. The new palaeobotanical evidence conflicts with previous hypotheses based on extant groups that interpret morphological simplicity as the plesiomorphic condition in the gametophytes of vascular plants. These new data indicate that a significant elaboration of both gametophyte and sporophyte occurred early in the tracheophyte lineage, and that the gametophytes of extant ‘pteridophytes’ are highly reduced compared to those of some of the earliest ‘protracheophytes’. Vestiges of this early morphological complexity may remain in the gametophytes of some extant groups such as Lycopodiaceae.     

Human dispersal and divergence

Dispersal, mate exchange and behavioral innovations leading to cultural dominance and replacement have obscured some of the relationships between major linguistic groups and the biological characteristics of their speakers. Recent phylogenetic reconstructions based on nuclear and mitochondrial genes have resulted in a series of hypotheses about the spread of modern humans. These hypotheses are now being tested by linguistic reconstruction. Genes, language, archaeology and geography are sometimes congruent, but new methods to assess covariation in genetic and linguistic distances are becoming necessary.     

Systematics and biogeography of the New World species of Trichadenotecnum Enderlein (Insecta: Psocodea: 'Psocoptera': Psocidae)

The taxonomy of the New World species of the genus Trichadenotecnum is revised. A total of 44 species, including 29 new species, were treated. These species are classified into 12 monophyletic species groups, eight of them newly proposed here. Two species previously assigned to Trichadenotecnum , T. pichincha New & Thornton and T. sylvaticum Turner, are recognized as not belonging to this genus. Phylogenetic relationships among 16 previously and presently proposed species groups are estimated based on a data matrix of 58 morphological characters. Trees from these analyses support monophyly of Trichadenotecnum and the proposed species groups. The New World species were divided into three major clades. Based on the phylogenetic hypothesis and distributional pattern of the species groups, the biogeographical history of the New World Trichadenotecnum is discussed.  © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society , 2008, 153 , 651–723.     

Primary classification and phylogeny of the Polemoniaceae, with comments on molecular cladistics

The system of classification of the Polemoniaceae currently in use was published by Grant in 1959. Much new evidence concerning relationships in the family has been obtained by numerous workers since 1959, and the old system is in need of revision. A revised system down to the genus level, based on conventional and unconventional characters, including molecular evidence, is presented here. Nineteen genera are grouped into eight tribes and two subfamilies. Three new tribes are described: Acanthogilieae, Loeselieae, and Leptodactyloneae. Several genera are transferred to new groups. The phylogeny of the family is discussed in the light of both the older and new evidence. The approach used in constructing both the 1959 and new systems is that of evolutionary systematics. Two recent (1996, 1997) family-wide surveys of cpDNA and rDNA use cladistic methods of analysis to arrive at sets of major groups. Some of this molecular evidence has been adopted for the present revised system. However, much incongruence still exists between the new sets of clades, on the one hand, and the present revised system or the still-viable parts of the 1959 system on the other hand. The incongruences call for an examination and comparison of the contrasting methods of evolutionary systematics and molecular cladistics. A fundamental flaw in the 1996 and 1997 treatments is the attempt to classify plants on the basis of single-gene gene trees.     

Phylogenetic Patterns of Geographical and Ecological Diversification in the Subgenus Drosophila

Colonisation of new geographic regions and/or of new ecological resources can result in rapid species diversification into the new ecological niches available. Members of the subgenus Drosophila are distributed across the globe and show a large diversity of ecological niches. Furthermore, taxonomic classification of Drosophila includes the rank radiation, which refers to closely related species groups. Nevertheless, it has never been tested if these taxonomic radiations correspond to evolutionary radiations. Here we present a study of the patterns of diversification of Drosophila to test for increased diversification rates in relation to the geographic and ecological diversification processes. For this, we have estimated and dated a phylogeny of 218 species belonging to the major species groups of the subgenus. The obtained phylogenies are largely consistent with previous studies and indicate that the major groups appeared during the Oligocene/Miocene transition or early Miocene, characterized by a trend of climate warming with brief periods of glaciation. Ancestral reconstruction of geographic ranges and ecological resource use suggest at least two dispersals to the Neotropics from the ancestral Asiatic tropical disribution, and several transitions to specialized ecological resource use (mycophagous and cactophilic). Colonisation of new geographic regions and/or of new ecological resources can result in rapid species diversification into the new ecological niches available. However, diversification analyses show no significant support for adaptive radiations as a result of geographic dispersal or ecological resource shift. Also, cactophily has not resulted in an increase in the diversification rate of the repleta and related groups. It is thus concluded that the taxonomic radiations do not correspond to adaptive radiations.     

Evolution of modern birds revealed by mitogenomics: timing the radiation and origin of major orders

Mitochondrial (mt) genes and genomes are among the major sources of data for evolutionary studies in birds. This places mitogenomic studies in birds at the core of intense debates in avian evolutionary biology. Indeed, complete mt genomes are actively been used to unveil the phylogenetic relationships among major orders, whereas single genes (e.g., cytochrome c oxidase I [COX1]) are considered standard for species identification and defining species boundaries (DNA barcoding). In this investigation, we study the time of origin and evolutionary relationships among Neoaves orders using complete mt genomes. First, we were able to solve polytomies previously observed at the deep nodes of the Neoaves phylogeny by analyzing 80 mt genomes, including 17 new sequences reported in this investigation. As an example, we found evidence indicating that columbiforms and charadriforms are sister groups. Overall, our analyses indicate that by improving the taxonomic sampling, complete mt genomes can solve the evolutionary relationships among major bird groups. Second, we used our phylogenetic hypotheses to estimate the time of origin of major avian orders as a way to test if their diversification took place prior to the Cretaceous/Tertiary (K/T) boundary. Such timetrees were estimated using several molecular dating approaches and conservative calibration points. Whereas we found time estimates slightly younger than those reported by others, most of the major orders originated prior to the K/T boundary. Finally, we used our timetrees to estimate the rate of evolution of each mt gene. We found great variation on the mutation rates among mt genes and within different bird groups. COX1 was the gene with less variation among Neoaves orders and the one with the least amount of rate heterogeneity across lineages. Such findings support the choice of COX 1 among mt genes as target for developing DNA barcoding approaches in birds.     

Precambrian trace fossils and the rise of bilaterian animals

In this attempt to synthesize present knowledge into a coherent story, the Cambrian explosion is interpreted to represent a true adaptive radiation, an event similar to Phanerozoic radiation events in principle but unique in its possibilities. A model of bilaterian evolution helps explain how this particular event involved the sudden initiation of major coelomate phyla. In many of these groups, preservable skeletons are part of the basic body plan. Biochemical‐sequence analyses indicate that acoelomates and pseudocoelomates branched off long before the coelomate radiation. The great differences between Vendian and Cambrian ichnofaunas, therefore, may be the result of a major shift in composition from Vendian acoelomate‐pseudocoelomate‐procoelomate faunas to Phanerozoic faunas dominated by new coelomate groups.     

The phylogeny of the Rhinocerotoidea (Mammalia, Perissodactyla)

A new phylogeny of the Superfamily Rhinocerotoidea is proposed, based upon an analysis of shared derived characters of the skull, teeth and skeleton. Hyrachyus is considered the primitive sister-taxon of the three rhinocerotoid families (Amynodontidae, Hyracodontidae, Rhinocerotidae), and the amynodonts appear to be the sister-group of hyracodonts and rhinocerotids. The relationships of primitive hyracodonts and rhinocerotids are clarified. Menoceras and Pleuroceras (new Subfamily Menoceratinae) are removed from the Diceratheriinae, since they appear to be more closely related to higher rhinoceroses than they are to Diceratherium. Of the three major monophyletic groups of higher rhinocerotids (aceratherines, teleoceratines and rhinocerotines), the last two groups are more closely related to each other than either is to aceratherines. Toxotherium and Schizotheroides are tentatively removed from the Rhinocerotoidea and placed in the Lophiodontidae.     

蜘蛛多肽毒素研究进展

蜘蛛肽类神经毒素按分子量大小可分为2种,除了黑寡妇蜘蛛毒素属于高分子量多肽,其余的毒素均属于小分子量肽类。不同的多肽毒素其功能不同,它们或仅作用于昆虫,或仅作用于哺乳动物,或对二者皆有影响。本文综述了近十年来这方面的研究成果,根据功能将毒素分成4类,逐一介绍了毒素的结构与作用机制。这些毒素的研究对神经生物学,新药的研究与开发及植物的抗虫育种等方面的发展具有重要的意义。