The evolutionary expansion of the Sporozoa

The sporozoans comprise a coherent group of protozoans, with characteristic and complex life cycles, containing 4–5000 species parasitic in invertebrates, particularly annelids and arthropods, and vertebrates. The group is a very successful one but neither its origins nor evolution are well understood. Considerations of traditional life cycles combined with newer molecular methodologies have thrown some light on the evolutionary expansions of the main groups of sporozoans, the gregarines, coccidia, haemosporidians and piroplasms. The sporozoans of economic importance such as the coccidia, malaria parasites and piroplasms have received most attention but the data obtained have also thrown new light on the possible evolution of less well studied groups and it is concluded that conclusions based on simple comparisons of life cycles will have to be modified. It is also clear that humans have played a major part in affecting the distribution and present abundance of many sporozoans of economic significance and probably also those of less importance, and that the rates of evolutionary expansion are much more rapid than previously thought.     

Redescription of Cosmocephalus tanakai Rodrigues & Vicente (Nematoda: Acuariidae), a parasite of the southern black-backed gull in New Zealand

Abstract

Cosmocephalus tanakai is redescribed from specimens found in the oesophagus of Larus dominicanus from the South Island of New Zealand. The male is characterised by nine pairs of pedunculate subventral caudal papillae plus two pairs of sessile papillae, and a pair of bicuspid papillae three-quarters of the way down the body. The female too has the pair of posteriad bicuspid papillae, plus a button-like terminal caudal process. A key to the species of Cosmocephalus is given.     

The evolutionary expansion and host-parasite relationships of the Digenea

Relevant data on the Digenea extracted from a host-parasite data-base are analysed in relation to host-groups, host-specificity, speciation, radiation and geographical distribution. The classification, evolution, co-evolution, and co-speciation of the group are discussed. Principal components analyses indicated that 119 families formed 11 groups in relation to their vertebrate hosts and the 55 families with molluscan records formed 6 groups in relation to their molluscan hosts. The most prominent host-groups are the Fish and Mammals. Individual digenean families did not exhibit the host combinations Fish + Birds, Fish + Mammals, Herpetiles + Birds and Herpetiles + Mammals. Families with Fish hosts tended to use Prosobranch and, to a lesser extent Bivalve, molluscs, whereas families in Herpetiles, Birds and Mammals tended to use Pulmonates. Families using 3 or 4 mixed vertebrate groups tended to use mixed molluscan groups. Families using Herpetiles as the vertebrate host tend to be the most host-specific and the least speciose, whereas those using 3 to 4 mixed vertebrate groups are the most speciose. In a detailed examination of three zoogonid genera, few indications of co-evolution with their vertebrate hosts were detected, and geographical information from the data-base appeared to shed no light upon the geographical origins of the Digenea. Some of these findings are commented upon in relation to the evolution of the Digenea.     

The structure of microbial evolutionary theory

The study of microbial phylogeny and evolution has emerged as an interdisciplinary synthesis, divergent in both methods and concepts from the classical evolutionary biology. The deployment of macromolecular sequencing in microbial classification has provided a deep evolutionary taxonomy hitherto deemed impossible. Microbial phylogenetics has greatly transformed the landscape of evolutionary biology, not only in revitalizing the field in the pursuit of life's history over billions of years, but also in transcending the structure of thought that has shaped evolutionary theory since the time of Darwin. A trio of primary phylogenetic lineages, along with the recognition of symbiosis and lateral gene transfer as fundamental processes of evolutionary innovation, are core principles of microbial evolutionary biology today. Their scope and significance remain contentious among evolutionists.     

The phylogeny of lower Hymenoptera (Insecta), with a summary of the early evolutionary history of the order

A cladistic analysis of the lower Hymenoptera, including all the ‘symphytan’ families and the apocritan families Stephanidae, Megalyridae, Trigonalyidae, Ibaliidae, Vespidae and Gasteruptiidae, has been undertaken. A total of 98 characters were scored for 21 taxa. Twenty equally parsimonious minimum-length trees were obtained. The phylogenetic status of the Xyelidae is uncertain: they might be monophyletic. or the Xyelinae might be the sistergroup of the rest of the Hymenoptera. The non-xyelid Hymenoptera are probably monophyletic; the phylogeny Tenthredinoidea + (Megalodontoidea + (Cephidae + (Anaxyelidea + (Siricidae + (Xiphydriidae + (Orussidae + Apocrita)))))) is proposed for this clade. The Blasticotomidae are probably the sistergroup of all othe Tenthredinoidea, but tenthredinoid phylogeny is otherwise uncertain. Substantial homoplasy occurs within the ‘siricoid’ families, making the relative positions of the Anaxyelidae and Siricidae uncertain. The Stephanidae might be the sistergroup of the rest of the Apocrita; the phylogeny of the remaining apocritan taxa included is insufficiently elucidated. The phylogeny proposed here supports the hypothesis that the appearance of parasitism in the Hymenoptera took place in the common ancestor of Orussidae + Apocrita, the host of which was probably wood boring insect larvae. The exact larval mode of feeding of the ancestral hymenopteran cannot be determined due ot the diversity of lifestyles in the basal lineages of the order.     

台湾海峡鱼类寄生线虫种类记述Ⅰ（线虫纲：毛首目：毛细科; 旋尾目：龙线虫科）

在历时近两年的研究中 ,检查了采自台湾浅滩渔场的近百种鱼类 ,检获线虫成虫 17种 ,隶属 9科 13属。其中 5种为新种 ,5属为中国海域寄生线虫属的首次记录。 2新种为蓝圆毛细线虫Capillariadecapterisp nov 和金线鱼嗜子宫线虫Philometranemipterisp nov ,并对 2已知种的分类地位作了调正。     

Early evolutionary origin of the planktic foraminifera inferred from small subunit rDNA sequence comparisons

Phylogenetic analysis of five partial planktic foraminiferal small subunit (SSU) ribosomal (r) DNA sequences with representatives of a diverse range of eukaryote, archaebacterial, and eubacterial taxa has revealed that the evolutionary origin of the foraminiferal lineage precedes the rapid eukaryote diversification represented by the crown of the eukaryotic tree and probably represents one of the earliest splits among extant free-living aerobic eukaryotes. The foraminiferal rDNA sequences could be clearly separated from known symbionts, commensals, and food organisms. All five species formed a single monophyletic group distinguished from the crown group by unique foraminiferal specific insertions as well as considerable nucleotide distance in aligned regions.     

Molecular data and the evolutionary history of dinoflagellates

We have sequenced small-subunit (SSU) ribosomal RNA (rRNA) genes from 16 dinoflagellates, produced phylogenetic trees of the group containing 105 taxa, and combined small- and partial large-subunit (LSU) rRNA data to produce new phylogenetic trees. We compare phylogenetic trees based on dinoflagellate rRNA and protein genes with established hypotheses of dinoflagellate evolution based on morphological data. Protein-gene trees have too few species for meaningful in-group phylogenetic analyses, but provide important insights on the phylogenetic position of dinoflagellates as a whole, on the identity of their close relatives, and on specific questions of evolutionary history. Phylogenetic trees obtained from dinoflagellate SSU rRNA genes are generally poorly resolved, but include by far the most species and some well-supported clades. Combined analyses of SSU and LSU somewhat improve support for several nodes, but are still weakly resolved. All analyses agree on the placement of dinoflagellates with ciliates and apicomplexans (=Sporozoa) in a well-supported clade, the alveolates. The closest relatives to dinokaryotic dinoflagellates appear to be apicomplexans, Perkinsus, Parvilucifera, syndinians and Oxyrrhis. The position of Noctiluca scintillans is unstable, while Blastodiniales as currently circumscribed seems polyphyletic. The same is true for Gymnodiniales: all phylogenetic trees examined (SSU and LSU-based) suggest that thecal plates have been lost repeatedly during dinoflagellate evolution. It is unclear whether any gymnodinialean clades originated before the theca. Peridiniales appear to be a paraphyletic group from which other dinoflagellate orders like Prorocentrales, Dinophysiales, most Gymnodiniales, and possibly also Gonyaulacales originated. Dinophysiales and Suessiales are strongly supported holophyletic groups, as is Gonyaulacales, although with more modest support. Prorocentrales is a monophyletic group only in some LSU-based trees. Within Gonyaulacales, molecular data broadly agree with classificatory schemes based on morphology. Implications of this taxonomic scheme for the evolution of selected dinoflagellate features (the nucleus, mitosis, flagella and photosynthesis) are discussed.     

Coding of intraspecific nucleotide polymorphisms: A tool to resolve reticulate evolutionary relationships in the ITS of beech trees (Fagus L., Fagaceae)

The internal transcribed spacers ITS1 and ITS2 of the nuclear ribosomal DNA (rDNA) have recently been found to display remarkable intraspecific polymorphism, a feature suggested as limiting their value for phylogenetic reconstructions. A comparative study of oligonucleotide motives and intraindividual nucleotide variability across all species of the tree genus Fagus (beech) shows, however, that this intraspecific ITS polymorphism follows a particular pattern, which can be used to detect reticulation and ancient polymorphism within the genus. Coding ITS polymorphisms as phylogenetically informative characters, moreover, resulted in better‐resolved phylogenies than traditional ‘base‐per‐base’ maximum parsimony and maximum likelihood analyses.     

Morphology of locomotor appendages in Arachnida: evolutionary trends and phylogenetic implications

The morphological diversity of locomotor appendages in Arachnida is surveyed lo reconstruct phylogenetic relationships and discover evolutionary trends in form and function. The appendicular skeleton and musculature of representatives from the ten living arachnid orders ate described, and a system of homology is proposed. Character polarities are established through comparison with an outgroup. Limulus polyphemus Xiphosura). Cladistic analysis suggests that Arachnida is monophyletic and that absence of extensor muscles is a primitive condition. Extensors are primitively absent in Araneae. Amblypygi, Uropygi, Palpigradi, Ricinulei and Acari. Most similarities in the appendages of these orders are symplesiomorphic so that phylogenetic relationships among the 'extensorless' groups cannot be resolved solely on the basis of appendicular characters. Extensor muscles appear to have evolved once, and their presence is considered a synapomorphic feature of Opiliones, Scorpiones, Pseudoscorpiones and Solifugae. Solifugae lack extensors, but a parsimonious interpretation of other characters indicates that this is a secondary, derived condition. The phylogenetic relationships among these four orders are clarified by modifications of the patellotibial joint. Cladistic analysis indicates that Opiliones may be the sister group of the other three orders and that Scorpiones is the sister group of Pseudoscorpiones and Solifugae. Conclusions concerning phylogenetic relationships and evolutionary morphology presented here differ substantially from those of earlier studies on the locomotor appendages of Arachnida.     

Review of the ultrastructure of the nematode body cuticle and its phylogenetic interpretation

The phylogenetic interpretation of the nematode cuticle ultrastructure is reviewed within the framework of recent DNA-sequence data. In particular, the structure of the median and basal zones is discussed. Several structural elements of the cuticle seem to have arisen independently several times within the Nematoda and thus are highly homoplasious (e.g. the cortical or basal radial striae, spiral fibre layers and a fluid matrix with struts). Moreover, identifying the homology of the nematode cuticle ultrastructures is often very difficult at deep taxonomic levels. Hence, the cuticle appears to be unreliable regarding resolution of deep-level relationships in the Nematoda. However, at less inclusive taxonomic levels (e.g. families, genera, ...) the cuticle seems to be a more reliable phylogenetic marker.     

Long-term evolutionary stability of bacterial endosymbiosis in curculionoidea: additional evidence of symbiont replacement in the dryophthoridae family

Bacterial intracellular symbiosis (endosymbiosis) is well documentedin the insect world where it is believed to play a crucial rolein adaptation and evolution. However, although Coleopteran insectsare of huge ecological and economical interest, endosymbiontmolecular analysis is limited to the Dryophthoridae family.Here, we have analyzed the intracellular symbiotic bacteriain 2 Hylobius species belonging to the Molytinae subfamily (Curculionoideasuperfamily) that exhibit different features from the Dryophthoridaeinsects in terms of their ecology and geographical spanning.Fluorescence in situ hybridization has shown that both Hylobiusspecies harbor rod-shaped pleiomorphic symbiotic bacteria inthe oocyte and in the bacteria-bearing organ (the bacteriome),with a shape and location similar to those of the Dryophthoridaebacteriome. Phylogenetic analysis of the 16S ribosomal DNA genesequences, using the heterogeneous model of DNA evolution, hasplaced the Hylobius spp. endosymbionts (H-group) at the basalposition of the ancestral R-clade of Dryophthoridae endosymbiontsnamed Candidatus Nardonella but relatively distant from theS-clade of Sitophilus spp. endosymbionts. Endosymbionts fromthe H-group and the R-clade evolved more quickly compared withfree-living enteric bacteria and endosymbionts from the S- andD-clades of Dryophthoridae. They are AT biased (58.3% A + T),and they exhibit AT-rich insertions at the same position aspreviously described in the Candidatus Nardonella 16S rDNA sequence.Moreover, the host phylogenetic tree based on the mitochondrialCOI gene was shown to be highly congruent with the H-group andthe R-clade, the divergence of which was estimated to be around125 MYA. These new molecular data show that endosymbiosis isold in Curculionids, going back at least to the common ancestorof Molytinae and Dryophthoridae, and is evolutionary stable,except in 2 Dryophthoridae clades, providing additional andindependent supplementary evidence for endosymbiont replacementin these taxa.     

Interspecies relationships among ADP-ribosylation factors (ARFs): Evidence of evolutionary pressure to maintain individual identities

ADP-ribosylation factors (ARFs) are ～20-kDa guanine nucleotide-binding proteins that are allosteric activators of the NAD:arginine ADP-ribosyltransferase activity of cholera toxin and appear to play a role in intracellular vesicular trafficking. Although the physiological roles of these proteins have not been defined, it has been presumed that each has a specific intracellular function. To obtain genetic evidence that each ARF is under evolutionary pressure to maintain its structure, and presumably function, rat ARF cDNA clones were isolated and their nucleotide and deduced amino acid sequences were compared to those of other mammalian ARFs. Deduced amino acid sequences for rat ARFs 1, 2, 3, 5 and 6 were identical to those of the known cognate human and bovine ARFs; rat ARF4 was 96% identical to human ARF4. Nucleotide sequences of both the untranslated as well as the coding regions were highly conserved. These results indicate that the ARF proteins are, as a family, extraordinarily well conserved across mammalian species. The unusually high degree of conservation of the untranslated regions is consistent with these regions having important regulatory roles and that individual ARFs contain structurally unique elements required for specific functions.     

毛蚜属Chaitophorus蚜虫(半翅目:蚜科:毛蚜亚科)与初级内共生菌Buchnera的演化关系

【目的】蚜虫体内共生菌种类丰富,二者关系十分密切。几乎所有蚜虫都具有一类专性的初级内共生菌Buchnera aphidicola,二者的专性共生关系使蚜虫-Buchnera成为研究共生关系演化的理想模型。本研究对蚜虫-Buchnera在低级阶元水平上的"平行演化假说"进行了验证。【方法】选取在杨属Populus或柳属Salix植物上营同寄主全周期生活的毛蚜属Chaitophorus蚜虫作为研究对象,基于不同来源的分子标记(蚜虫线粒体基因、核基因和内共生菌基因),运用最大似然法和贝叶斯法重建蚜虫和Buchnera的系统树,并利用Tree Map、Jane和Para Fit检验二者是否具有协同系统发生关系。【结果】Tree Map和Jane分析检测到毛蚜属蚜虫与Buchnera具有显著的共成种信号,Para Fit分析结果表明二者的总体关联极为显著。【结论】毛蚜属蚜虫与其初级内共生菌Buchnera在种级及以下水平上符合"平行演化假说",并且二者的演化关系不会受到寄主植物差异的影响。     

Monophyly of the family Desmoscolecidae (Nematoda,Demoscolecida) and Its Phylogenetic position inferred from 18S rDNA sequences

To infer the monophyletic origin and phylogenetic relationships of the order Desmoscolecida, a unique and puzzling group of mainly free-living marine nematodes, we newly determined nearly complete 18S rDNA sequences for six marine desmoscolecid nematodes belonging to four genera (Desmoscolex, Greeffiella, Tricoma and Paratricoma). Based on the present data and those of 72 nematode species previously reported, the first molecular phylogenetic analysis focusing on Desmoscolecida was done by using neighbor joining (NJ), maximum parsimony (MP), maximum likelihood (ML) and Bayesian inference (BI) methods. All four resultant trees consistently and strongly supported that the family Desmoscolecidae forms a monophyletic group with very high node confidence values. The monophyletic clade of desmocolecid nematodes was placed as a sister group of the clade including some members of Monhysterida and Araeolaimida, Cyartonema elegans (Cyartonematidae) and Terschellingia longicaudata (Linhomoeidae) in all the analyses. However, the present phylogenetic trees do not show any direct attraction between the families Desmoscolecidae and Cyartonematidae. Within the monophyletic clade of the family Desmoscolecidae in all of the present phylogenetic trees, there were consistently observed two distinct sub-groups which correspond to the subfamilies Desmoscolecinae [Greeffiella sp. + Desmoscolex sp.] and Tricominae [Paratricoma sp. + Tricoma sp].     

Unexpected evolutionary diversity in a recently extinct Caribbean mammal radiation

Identifying general patterns of colonization and radiation in island faunas is often hindered by past human-caused extinctions. The insular Caribbean is one of the only complex oceanic-type island systems colonized by land mammals, but has witnessed the globally highest level of mammalian extinction during the Holocene. Using ancient DNA analysis, we reconstruct the evolutionary history of one of the Caribbean''s now-extinct major mammal groups, the insular radiation of oryzomyine rice rats. Despite the significant problems of recovering DNA from prehistoric tropical archaeological material, it was possible to identify two discrete Late Miocene colonizations of the main Lesser Antillean island chain from mainland South America by oryzomyine lineages that were only distantly related. A high level of phylogenetic diversification was observed within oryzomyines across the Lesser Antilles, even between allopatric populations on the same island bank. The timing of oryzomyine colonization is closely similar to the age of several other Caribbean vertebrate taxa, suggesting that geomorphological conditions during the Late Miocene facilitated broadly simultaneous overwater waif dispersal of many South American lineages to the Lesser Antilles. These data provide an important baseline by which to further develop the Caribbean as a unique workshop for studying island evolution.     

An early cell shape transition drives evolutionary expansion of the human forebrain

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