TRACE FOSSILS FROM THE PRECAMBRIAN AND BASAL CAMBRIAN

Certain worm-like configurations on rocks are recognized as shrinkage-crack infillings. Some genuine Precambrian trace fossils are briefly described. The early Cambrian contains a richer assemblage, including some distinctive and widespread form genera. The study of early trace fossils leads to conclusions not only on facies, but also on the evolution of behaviour and functional morphology in soft-bodied organisms.     

陕南地区下寒武统筇竹寺阶软舌螺化石

描述陕南地区下寒武统筇竹寺阶软舌螺化石６属８种,其中有５新属（Ningqiangethus gen.nov.,Bilgulitheca gen.nov.,Xixiangethes gen.nov.,Paranicrocornus gen.no.,Inflatatheca gen.nov.),新种,１相似种,１未定种。从组织结构和面貌上论述筇竹寺阶软舌螺和梅树村阶软舌螺匠区别,筇笔直寺阶的软舌螺不仅个体增大、背腹分异、口唇发育、壳体与口盖常共存,而且属种分异度大,为进一步研究软舌螺动物的早期演化和解决下寒武统生物地层划分为对比提供重要的实证材料。     

Phylogeny of the platygastroid wasps (Hymenoptera) based on sequences from the 18S rRNA, 28S rRNA and cytochrome oxidase I genes: implications for the evolution of the ovipositor system and host relationships

The Platygastroidea are a diverse group of mostly small to tiny wasps, the common biology for which is endoparasitism of insect and spider eggs. No analytically‐based phylogeny exists for the superfamily, and the current suprageneric classification is flawed in part because of its reliance on homoplasious and pleisiomorphic morphological characters. To determine platygastroid relationships as a basis for investigating host and ovipositor evolution, phylogenies of > 70 in‐group species (representing 55 genera) were reconstructed by parsimony and Bayesian methods using three molecular markers; the mitochondrial cytochrome oxidase I and the nuclear genes 28S and 18S rRNA. The results strongly support the monophyly of the superfamily and one of the two families, Platygastridae, but the Scelionidae are most likely polyphyletic. However, within the Scelionidae, there is a well supported ‘main scelionid clade’ that contains the majority of genera assigned to the family. At the subfamilial level, both putative subfamilies of Platygastridae, the Platygastrinae, and Sceliotrachelinae, are likely to be polyphyletic. Within the Scelionidae, both the Teleasinae and Telenominae are monophyletic, but the Scelioninae is clearly not so. The current tribal classification for the Scelionidae is in need of major reassessment because no tribes, with the exception of the Scelionini s.s., were found to be monophyletic. Further illustrating the problems associated with the current classification is the nonmonophyly of a number of genera, namely Opisthacantha Caloteleia, Telenomus, Trimorus, Teleas and Idris. Analysis of ovipositor evolution in the superfamily revealed that the Ceratobaeus‐type ovipositor system is ancestral; however, this trait was lost prior to the evolution of the main scelionid clade, for which the Scelio‐type ovipositor system is ancestral and defines a mostly paraphyletic assemblage. Ancestral state analysis indicates that the Ceratobaeus‐type ovipositor was subsequently re‐evolved in the main scelionid clade, representing a possible contradiction of Dollo’s law. Previously, the tribal placement has been used to predict the host associations of genera for which host data were unavailable. However, the fact that most tribes are not monophyletic throws into doubt any such speculation based on the current classification. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 91 , 653–669.     

Convergent evolution and paraphyly of the hawk-eagles of the genus Spizaetus (Aves, Accipitridae) – phylogenetic analyses based on mitochondrial markers

The phylogenetic relationships within the New and Old World hawk-eagle assemblage (genus Spizaetus ; Aves: Accipitridae) were studied using mitochondrial DNA sequences ( cytochrome b , control region). Eighty-four specimens representing all Spizaetus species and almost all currently distinguished subspecies as well as 11 other booted and non-booted 'eagle' genera from the Neotropics, Africa, Eurasia, South Asia and Australasia ( Oroaetus , Harpia , Morphnus , Lophaetus , Stephanoaetus , Hieraaetus , Aquila , Ictinaetus , Spilornis , Pithecophaga , Harpyopsis ) were investigated. Although the basal branching could not be resolved, our investigations clearly indicate that hawk-eagles represent a paraphyletic assemblage and thus their external similarities have to be ascribed to convergent evolution. The New World taxa of Spizaetus cluster together, but the South American species Oroaetus isidori appears embedded within this clade. The taxa from Southeast to East Asia form a clearly separated monophyletic group. It is further divided into two subgroups, which are also characterized by distinct juvenile plumage patterns. Spizaetus africanus , the only African representative of the genus, is found in a mixed cluster consisting of members of the genera Aquila and Hieraaetus . These findings are in accordance with previous studies of other authors based on various molecular markers and different sets of taxa, but disagree with current taxonomy. Therefore, we suggest assigning the species of the genus Spizaetus to three different genera: (1) Spizaetus (including Oroaetus isidori ) in Central and South America and (2) Nisaetus for the Southeast to East Asian group. (3) The African taxon ( Spizaetus africanus ) is discussed to be included into the genus Aquila. Furthermore, we propose to use the former genus name Lophotriorchis Sharpe, 1874, for the monotypic species Hieraaetus kienerii , which has an isolated phylogenetic position.     

Frugivore gape size and the evolution of fruit size and shape in southern hemisphere floras

Abstract The present study uses differences among frugivore faunas of the southern hemisphere landmasses to test whether frugivore characteristics have influenced the evolution of fruit traits. Strong floristic similarities exist among southern landmasses; for example, 75% of New Zealand vascular plant genera also have species in Australia. However, plants in Australia and South America have evolved in the presence of a range of mammalian frugivores, whereas those in New Zealand, New Caledonia and the Pacific Islands have not. In addition, the avian frugivores in New Zealand and New Caledonia are generally smaller than those of Australia. If frugivore characteristics have influenced the evolution of fruit traits, predictable differences should exist between southern hemisphere fruits, particularly fruit size and shape. Fruit dimensions were measured for 77 New Zealand species and 31 Australian species in trans‐Tasman genera. New Zealand fruits became significantly more ellipsoid in shape with increasing size. This is consistent with frugivore gape size imposing a selective pressure on fruit ingestability. This result is not a product of phylogenetic correlates, as fruit length and width scaled isometrically for Australian species in genera shared with New Zealand. Within‐genus contrasts between New Zealand and Australian species in 20 trans‐Tasman genera showed that New Zealand species have significantly smaller fruits than their Australian counterparts. Within‐genus contrasts between New Zealand and South American species in nine genera gave the same result; New Zealand species had significantly smaller fruits than their South American counterparts. No difference was found in fruit size or shape between New Zealand and New Caledonia congeneric species from 12 genera. These results are consistent with the broad characteristics of the frugivore assemblage influencing the evolution of fruit size and shape in related species. The smaller‐sized New Zealand frugivore assemblage has apparently influenced the evolution of fruit size of colonizing taxa sometimes within a relatively short evolutionary timeframe.     

5 The origin of the dinoflagellate plastid

The Dasycladales is an ancient order of tropical benthic marine green algae, unique in their radially arranged unicellular thalli and well-preserved fossil record due to extensive calcification of the thallus. The inference of an accurate phylogeny for the Dasycladales is important in order to better understand stratigraphy, character evolution, and classification. Previous analyses ( rbc L and 18S rDNA) suggested that the Family Acetabulariaceae is monophyletic, but that the Family Dasycladaceae is a basal paraphyletic assemblage. However, the two data sets disagreed regarding genus- and species-level relationships within the Dasycladales. For example, the placement of the genera, Halicoryne , Bornetella and Cymopolia were incongruent. Given the conflicting results of these previous analyses, the current project examined a third highly conserved nuclear-encoded gene, 26S rDNA. Aligned 26S rDNA sequences were analyzed with parsimony and model-based methods and compared to previous results based on18S and rbc L sequences. Family-level relationships based on 26S rDNA were congruent with previous studies: the Acetabulariaceae is monophyletic while the Dasycladaceae is paraphyletic. In addition, acetabulariacean genera are not monophyletic, suggesting that the presence of a corona inferior or calcification of gametes may not be appropriate to define genera. Within the Dasycladaceae, the basal position of Cymopolia is supported by 26S rDNA, a result congruent with rbcL and stratigraphy but not with 18S data. These results will be discussed in the context of morphological character evolution, fossil stratigraphy and family, tribal and generic relationships among these living algal fossils. Supported in part by NSF grant DEB-0128977 to FWZ.     

4 Phylogeny of the dasycladales (ulvophyceae,chlorophyta) based on analyses of nuclear‐encoded large subunit rDNA

The Dasycladales is an ancient order of tropical benthic marine green algae, unique in their radially arranged unicellular thalli and well‐preserved fossil record due to extensive calcification of the thallus. The inference of an accurate phylogeny for the Dasycladales is important in order to better understand stratigraphy, character evolution, and classification. Previous analyses (rbcL and 18S rDNA) suggested that the Family Acetabulariaceae is monophyletic, but that the Family Dasycladaceae is a basal paraphyletic assemblage. However, the two data sets disagreed regarding genus‐ and species‐level relationships within the Dasycladales. For example, the placement of the genera, Halicoryne, Bornetella and Cymopolia were incongruent. Given the conflicting results of these previous analyses, the current project examined a third highly conserved nuclear‐encoded gene, 26S rDNA. Aligned 26S rDNA sequences were analyzed with parsimony and model‐based methods and compared to previous results based on18S and rbcL sequences. Family‐level relationships based on 26S rDNA were congruent with previous studies: the Acetabulariaceae is monophyletic while the Dasycladaceae is paraphyletic. In addition, acetabulariacean genera are not monophyletic, suggesting that the presence of a corona inferior or calcification of gametes may not be appropriate to define genera. Within the Dasycladaceae, the basal position of Cymopolia is supported by 26S rDNA, a result congruent with rbcL and stratigraphy but not with 18S data. These results will be discussed in the context of morphological character evolution, fossil stratigraphy and family, tribal and generic relationships among these living algal fossils. Supported in part by NSF grant DEB‐0128977 to FWZ.     

First report of brachiopod–brachiopod endoparasitism

Schemm-Gregory, M. & Sutton, M. 2010: First report of brachiopod–brachiopod endoparasitism. Lethaia , Vol. 43, pp. 111–115.
The first example of brachiopod–brachiopod endoparasitism is reported from the Lower Devonian of China. Three-dimensional reconstructions following serial sectioning show a specimen of a strophomenide ( Dicoelostrophia sp.) within an articulated shell of the spiriferide Rostrospirifer tonkinensis ; morphological modifications of the host and the positioning of the strophomenide with respect to the inhalant current demonstrate the in vivo nature of the association. The symbiosis is interpreted as parasitic; it appears to be facultative but demonstrates the viability of this mode of life, expanding the ecological range known to be exploitable by the Brachiopoda. □ 3-D reconstruction , Brachiopoda , Dicoelostrophia , endoparasitism , Lower Devonian , Rostrospirifer .     

Relationships of microsporidian genera, with emphasis on the polysporous genera, revealed by sequences of the largest subunit of RNA polymerase II (RPB1)

Molecular data have proved useful as an alternative to morphological data in showing the relationships of genera within the phylum Microsporidia, but until now have been available only for ribosomal genes. In previous studies protein-coding genes of microsporidia have been used only to assess their position in the evolution of eukaryotes. For the first time we report on the use of a protein-coding gene, the A-G region of the largest subunit of RNA polymerase II (RPB1) from 14 mainly polysporous species, to generate an alternative phylogeny for microsporidia. Using the amino acid sequences, the genera and species fell into the same main groupings as had been obtained with 16S rDNA sequences, but the RPB1 data provided better resolution within these groups. The results supported the pairings of Trachipleistophora hominis with Vavraia culicis and Pleistophora hippoglossoideos with Pleistophora typicalis. They also confirmed that the genus Pleistophora is not monophyletic and that it will be necessary to transfer Pleistophora ovariae and Pleistophora mirandellae into one or more other genera, as has already been effected for Pleistophora anguillarum.     

Revision of the Nearctic species of the genus Stiropius Cameron (=Bucculatriplex Auct.) with the description of a new related genus (Hymenoptera: Braconidae)

Abstract. The New World rogadine genus Stiropius Cameron is revised for the Nearctic region and a new related genus from the Americas, Viridipyge , is decribed. Bucculatriplex Viereck is found to be a junior subjective synonym of Stiropius Cameron. Three Nearctic species are recognized: S.bucculatricis (Ashmead) comb.n., S.californicus sp.n. and S.wagneri sp.n. A single Nearctic specis of Viridipyge is described as new: V.prunicola , and a Neotropical species, V.letifer (Mann) comb.n., is found to be congeneric. The biology and systematic relationships of both genera are discussed; the two genera appear to represent a relatively basal branch of the Rogadini lineage.     

湖北宜昌奥陶系庙坡组疑源类

湖北宜昌地区庙坡组是达瑞威尔阶/桑比阶界线附近的地层,该段地层产出分异度较高,丰度适中的疑源类组合。该组合包括16属,28种,其中7个未定命名种,可与国内、外同期疑源类组合进行对比。庙坡组疑源类组合既产出晚奥陶世特征分子,也产出阿伦尼格期(弗洛阶上部—达瑞威尔阶底部)的特征分子,显示出一定的过渡特色。组合以Baltisphaeridium(17%—52%),Leiosphaeridia(6%—78%)占优势;反映了其沉积环境为离岸较远的外陆棚环境。     

Evolutionary relationships among ammonia- and nitrite-oxidizing bacteria.

Comparative 16S rRNA sequencing was used to evaluate phylogenetic relationships among selected strains of ammonia- and nitrite-oxidizing bacteria. All characterized strains were shown to be affiliated with the proteobacteria. The study extended recent 16S rRNA-based studies of phylogenetic diversity among nitrifiers by the comparison of eight strains of the genus Nitrobacter and representatives of the genera Nitrospira and Nitrospina. The later genera were shown to be affiliated with the delta subdivision of the proteobacteria but did not share a specific relationship to each other or to other members of the delta subdivision. All characterized Nitrobacter strains constituted a closely related assemblage within the alpha subdivision of the proteobacteria. As previously observed, all ammonia-oxidizing genera except Nitrosococcus oceanus constitute a monophyletic assemblage within the beta subdivision of the proteobacteria. Errors in the 16S rRNA sequences for two strains previously deposited in the databases by other investigators (Nitrosolobus multiformis C-71 and Nitrospira briensis C-128) were corrected. Consideration of physiology and phylogenetic distribution suggested that nitrite-oxidizing bacteria of the alpha and gamma subdivisions are derived from immediate photosynthetic ancestry. Each nitrifier retains the general structural features of the specific ancestor's photosynthetic membrane complex. Thus, the nitrifiers, as a group, apparently are not derived from an ancestral nitrifying phenotype.     

Molecular phylogeny of the Tylenchina and evolution of the female gonoduct (Nematoda: Rhabditida)

Tylenchina are a morphologically and functionally diverse group of nematode species that range from free-living bacteriovores, over transitory grazing root-hair feeders to highly specialized plant-parasites with complex host associations. We performed phylogenetic analyses of small subunit rDNA sequences from 97 species including an analysis that account for the RNA secondary structure in the models of evolution. The present study confirms the sister relationship of the bacteriovore Cephalobidae with the predominantly plant-parasitic Tylenchomorpha. All analyses appoint the fungal-feeding Aphelenchidae and Aphelenchoididae as being polyphyletic but the morphology based hypothesis of their monophyly could not be significantly rejected. Within the Tylenchomorpha, the families that exclusively parasitize higher plants are joined in a single clade. However, only the monophyletic position of the (super)families Hoplolaimidae and Criconematoidea were supported; Anguinidae, Tylenchidae, Belonolaimidae and Pratylenchidae appeared to be paraphyletic or polyphyletic. Parsimony and likelihood ancestral state reconstruction revealed that burrowing endoparasitism and sedentary endoparasitism each evolved, respectively, at least six and at least three times independently, mostly from migratory ectoparasitic ancestors. Only root-knot nematodes have evolved from burrowing endoparasitic nematodes. Traditional classifications are partially misled by this convergent evolution of feeding type and associated morphology. Contrastingly, mapping attributes of the gonoduct cellular architecture, including newly obtained data of 18 species belonging to the Aphelenchoidea, Criconematoidea, Anguinidae and Panagrolaimidae, revealed a broad congruence of the gonoduct characters and the molecular phylogenetic hypothesis. Yet, the presence of an offset spermatheca and proliferation of uterus cells has evolved multiple times, the latter associated with derived endoparasitic feeding specialization and resulting reproduction mode. Ancestral state reconstruction further revealed that the gonoduct of the morphologically and ecologically dissimilar tylenchid and cephalobid nematodes evolved from a common ancestor.     

Ovipositor internal microsculpture in the Braconidae (Insecta, Hymenoptera)

Variation in the microsculpture of the ovipositor egg canal, the morphology of the tip of the upper valve, the structure of the valvillus and the apex of the lower valve seals, as revealed by scanning electron microscopy is described for members of 52 genera representing 30 subfamilies of Braconidae. The possible phylogenetic implications of this variation are discussed. Characters supporting monophyly of the cyclostome clade, and of the non-cyclostome subfamilies Agathidinae, Pselaphaninae and Sigalphinae are reported. Functional and phylogenetic implications are discussed and possible convergent evolution of some features associated with endoparasitism are considered in the light of recent molecular systematics findings. © 1998 The Norwegian Academy of Science and Letters     

Axes of differentiation in the bower-building cichlids of Lake Malawi

The 500-1000 cichlid species endemic to Lake Malawi constitute one of the most rapid and extensive radiations of vertebrates known. There is a growing debate over the role natural and sexual selection have played in creating this remarkable assemblage of species. Phylogenetic analysis of the Lake Malawi species flock has been confounded by the lack of appropriate morphological characters and an exceptional rate of speciation, which has allowed ancestral molecular polymorphisms to persist within species. To overcome this problem we used amplified fragment length polymorphism (AFLP) to reconstruct the evolution of species within three genera of Lake Malawi sand-dwelling cichlids that construct elaborate male display platforms, or bowers. Sister taxa with distinct bower morphologies, and that exist in discrete leks separated by only 1-2 m of depth, are divergent in both sexually selected and ecological traits. Our phylogeny suggests that the forces of sexual and ecological selection are intertwined during the speciation of this group and that specific bower characteristics and trophic morphologies have evolved repeatedly. These results suggest that trophic morphology and bower form may be inappropriate characters for delineating taxonomic lineages. Specifically the morphological characters used to describe the genera Lethrinops and Tramitichromis do not define monophyletic clades. Using a combination of behavioural and genetic characters, we were able to identify several cryptic cichlid species on a single beach, which suggests that sand dweller species richness has been severely underestimated.     

Osteology and phylogenetic interrelationships of sturgeons (Acipenseridae)

Sturgeons (Acipenseridae) are an ancient and unique assemblage of fishes historically important to discussions of actinopterygian evolution. Despite their basal position within Actinopterygii, rigorous comparative morphological studies of acipenserids have never been made, and most ideas about acipenserid evolution hinge on an untested impression that shovelnose sturgeons (Scaphirhynchini) are phylogenetically primitive. This impression promoted ideas that: (1) the earliest acipenserids were highly benthic and evolved secondarily into pelagic predators, and (2) paedomorphosis has dominated mechanisms affecting their morphological change. Using cladistic methods, this study examines generic level interrelationships within Acipenseridae. Representatives of the four acipenserid genera Huso, Acipenser, Pseudoscaphirhynchus, and Scaphirhynchus, as well as their acipenseriform outgroups Polyodontidae, Peipiaosteidae, and Chondrosteidae, were surveyed for skeletal characters. Sixty-nine characters are identified and described to support the first generic level cladogram of Acipenseridae. Huso is phylogenetically primitive within Acipenseridae and the sister group to a redefined subfamily Acipenserinae. Acipenser is not supported by any characters identified in this study, but the tribe Scaphirhynchini comprising Scaphirhynchus and Pseudoscaphirhynchus is found to be monophyletic. The cladogram contradicts historical ideas about acipenserid evolution because Huso defines an outgroup morphology and life history founded on pelagic habitats and piscivory. In contrast, acipenserines, and more markedly scaphirhynchines, are benthic predators possessing character complexes for benthic feeding, respiration, locomotion, and protection. Also, the pattern of character acquisition within Acipenseridae suggests that peramorphosis played a central role in acipenserid evolution. Peramorphic addition and enlargement of the skeleton and scalation defines most characters at all nodes within Acipenseridae, and repudiates paedomorphosis as a major trend in evolution within the family Acipenseridae.     

The gastropod–crustacean connection: towards the phylogeny and evolution of the parasitic copepod family Splanchnotrophidae

Amongst the most significant metazoan taxa associated with gastropod molluscs is the endoparasitic copepod family Splanchnotrophidae. Currently it contains five genera with highly modified morphology and exclusively infesting nudibranch and sacoglossan sea slug hosts. The present study is a first approach towards reconstructing their phylogeny and evolution. Cladistic analysis of 109 morphological characters including 24 known splanchnotrophid species resulted in a fully resolved strict consensus tree that is discussed in morphological, functional, and geographical frameworks. Alternative topologies are also explored. Originating from paraphyletic Philoblennidae, the Splanchnotrophidae emerge as sister group to the genus Briarella. Unique synapomorphies, such as the bizarre body shapes and successive reduction of mouthparts, are discussed as adaptive traits to endoparasitism that evolved only once within copepods infesting shell‐less heterobranch gastropods. The ancestrally Indo‐Pacific Splanchnotrophidae split up into a clade of the still Indo‐Pacific genera Ceratosomicola and Arthurius, sister to a clade composed of the monophyletic amphi‐American genus Ismaila and European Splanchnotrophus emerging from paraphyletic Lomanoticola. Although initial radiation of Briarella and Splanchnotrophidae is likely to have involved chromodoridid nudibranch hosts, later phylogenies of parasites and their hosts are incongruent; intriguingly, host shifts from nudibranch to only distantly related sacoglossan species occurred at least two times independently. Such remarkable ecological plasticity is assumed to have driven splanchnotrophid diversification. Topological hypotheses and historical biogeographical and evolutionary scenarios inferred herein can be tested by future molecular research. © 2013 The Linnean Society of London     

Systematic and comparative anatomy of Cymbidieae (Orchidaceae)

Cymbideae comprise an assemblage of 28 genera nearly all of which are represented in this study. Their anatomy is relatively homogenous with the exception of Govenia , in which roots lack velamen and pseudobulb vascular bundles lack sclerenchyma, conditions that do not obtain in other genera. Marginal fibre bundles in leaves of Grammatophyllum and Porphyroglottis consist of clusters of thicker-walled, narrower, epidermis-facing fibres as well as thinner-walled, wider, mesophyll-facing fibres. This feature also occurs in some species of Maxillaria . Baculate tilosomes appear in the roots of a majority of genera in Cymbidieae, as they do in species of Maxillaria , confirming DNA analyses showing a close relationship between tribes Cymbidieae and Maxillarieae. Govenia is singled out both on anatomical and molecular grounds as being ill-placed in Cymbidieae. Cladistic analysis produces only a few tentative hypotheses of phylogenetic relationships among the 28 genera, showing that anatomical characters are of limited value in assessing affinities within this tribe. © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society , 2002, 139 , 1–27.     

Evolution of syncarpy and other morphological characters in African Annonaceae: a posterior mapping approach

The congenital fusion of carpels, or syncarpy, is considered a key innovation as it is found in more than 80% of angiosperms. Within the magnoliids however, syncarpy has rarely evolved. Two alternative evolutionary origins of syncarpy were suggested in order to explain the evolution of this feature: multiplication of a single carpel vs. fusion of a moderate number of carpels. The magnoliid family Annonaceae provides an ideal situation to test these hypotheses as two African genera, Isolona and Monodora, are syncarpous in an otherwise apocarpous family with multicarpellate and unicarpellate genera. In addition to syncarpy, the evolution of six other morphological characters was studied. Well-supported phylogenetic relationships of African Annonaceae and in particular those of Isolona and Monodora were reconstructed. Six plastid regions were sequenced and analyzed using maximum parsimony and Bayesian inference methods. The Bayesian posterior mapping approach to study character evolution was used as it accounts for both mapping and phylogenetic uncertainty, and also allows multiple state changes along the branches. Our phylogenetic analyses recovered a fully resolved clade comprising twelve genera endemic to Africa, including Isolona and Monodora, which was nested within the so-called long-branch clade. This is the largest and most species-rich clade of African genera identified to date within Annonaceae. The two syncarpous genera were inferred with maximum support to be sister to a clade characterized by genera with multicarpellate apocarpous gynoecia, supporting the hypothesis that syncarpy arose by fusion of a moderate number of carpels. This hypothesis was also favoured when studying the floral anatomy of both genera. Annonaceae provide the only case of a clear evolution of syncarpy within an otherwise apocarpous magnoliid family. The results presented here offer a better understanding of the evolution of syncarpy in Annonaceae and within angiosperms in general.     

Phylogeny of sharks of the family Triakidae (Carcharhiniformes) and its implications for the evolution of carcharhiniform placental viviparity

We present a study of inter- and intra-familial relationships of the carcharhiniform shark family Triakidae aimed at testing existing hypotheses of relationships for this group and at improving understanding of the evolution of reproductive traits in elasmobranchs. Our analyses and conclusions are based on evidence from DNA sequences of four protein-coding genes (three from the mitochondrial genome and a single copy nuclear gene) from eight of the nine genera and 20 of the 39 species currently assigned to the Triakidae. The sequence data offer strong support for the following previously proposed triakid clades: Galeorhinini (Hypogaleus+Galeorhinus); a subset of the Iagini (Furgaleus+Hemitriakis but not Iago); and part of the Triakinae (Mustelus, Scylliogaleus and part of Triakis). Interestingly, the molecular data provide considerable evidence of paraphyly of the genera Triakis and Mustelus. Our results suggest that the subgenera Triakis and Cazon of Triakis represent two distinct lineages that are only distantly related and that the genus Mustelus as currently defined does not constitute a monophyletic assemblage unless S. quecketti and some species of Triakis (subgenus Cazon) are included in Mustelus. Within our sample of species of Mustelus (including Cazon and Scylliogaleus), the sequence data support two well-defined clades that can be diagnosed by mode of reproduction (placental vs. aplacental species). The phylogenetic framework presented here is used to infer key events in the evolution and loss of placental viviparity among carcharhiniform sharks.