Home About us Contact
|
Home About us Contact | ||
|
|
||
Sister Groups (sister + groups)
Selected AbstractsAgnathan brain anatomy and craniate phylogenyACTA ZOOLOGICA, Issue 2009Roman Hossein Khonsari Abstract The central nervous system of hagfishes displays unique characteristics that are distinct from any other craniate neuroanatomic features. Whether these hagfish characters are general for all craniates, autapomorphies of hagfishes, or merely a derived state of the general cyclostome condition is still a matter of debate that relates to the question of the monophyly or paraphyly of the cyclostomes. The present cladistic study includes 123 neuroanatomical characters of nine chordate species and supports cyclostome paraphyly, in contrast to most current molecular sequence-based phylogenies, which support cyclostome monophyly. An understanding of the unique neural characters in hagfishes is critical to inspiring further comparative and developmental studies with regards to these two conflicting results and the very deep divergence between craniates and their presumed sister groups. The recent access to hagfish developmental data may provide exciting perspectives in the understanding and characterization of the basalmost craniate node and the interpretation of hagfish brain structure. [source] Use of dispersal,vicariance analysis in biogeography , a critiqueJOURNAL OF BIOGEOGRAPHY, Issue 1 2010Ullasa Kodandaramaiah Abstract Aim, Analytical methods are commonly used to identify historical processes of vicariance and dispersal in the evolution of taxa. Currently, dispersal,vicariance analysis implemented in the software diva is the most widely used method. Despite some recognized shortcomings of the method, it has been treated as error-free in many cases and used extensively as the sole method to reconstruct histories of taxa. In light of this, an evaluation of the limitations of the method is needed, especially in relation to several newer alternatives. Methods, In an approach similar to simulation studies in phylogenetics, I use hypothetical taxa evolving in specific geological scenarios and test how well diva reconstructs their histories. Results,diva reconstructs histories accurately when evolution has been simple; that is, where speciation is driven mainly by vicariance. Ancestral areas are wrongly identified under several conditions, including complex patterns of dispersals and within-area speciation events. Several potentially serious drawbacks in using diva for inferences in biogeography are discussed. These include the inability to distinguish between contiguous range expansions and across-barrier dispersals, a low probability of invoking extinctions, incorrect constraints set on the maximum number of areas by the user, and analysing the ingroup taxa without sister groups. Main conclusions, Most problems with inferences based on diva are linked to the inflexibility and simplicity of the assumptions used in the method. These are frequently invalid, resulting in spurious reconstructions. I argue that it might be dangerous to rely solely on diva optimization to infer the history of a group. I also argue that diva is not ideally suited to distinguishing between dispersal and vicariance because it cannot a priori take into account the age of divergences relative to the timing of barrier formation. I suggest that other alternative methods can be used to corroborate the findings in diva, increasing the robustness of biogeographic hypotheses. I compare some important alternatives and conclude that model-based approaches are promising. [source] Reconciling fossils and molecules: Cenozoic divergence of cichlid fishes and the biogeography of MadagascarJOURNAL OF BIOGEOGRAPHY, Issue 9 2001M. Vences Aim The biogeographical origins of the extant vertebrates endemic to Madagascar are largely unsolved, but have often been related to vicariance in the context of fragmentation of the supercontinent Gondwana in the Mesozoic. Such hypotheses are especially appealing in the case of cichlid fishes, which show phylogenetic relationships reflecting the temporal successions of the breakup of Gondwana. We used molecular clock data to test this assumption. Location Fragments of the 16S rRNA gene and of the nuclear Tmo-4C4 locus, partly obtained from Genbank from South American, African, Malagasy and Indian cichlids were analysed. Methods Based on monophyletic cichlid radiations in African lakes, we calibrated a molecular clock. The obtained rates were used to estimate the age of divergence of the major cichlid clades. Results The results agreed better with a Cenozoic than with a Mesozoic divergence, and were in accordance with the fossil record. Sequence divergences of the 16S and 12S rRNA genes of most lineages of Malagasy terrestrial and freshwater vertebrates from their non-Malagasy sister groups were below saturation and many were relatively similar to those of cichlids. Main conclusions A Cenozoic dispersal from continental landmasses may explain the origin of most extant Malagasy vertebrate groups better than a Jurassic/Cretaceous vicariance. [source] Estimating ancestral distributions of lineages with uncertain sister groups: a statistical approach to Dispersal,Vicariance Analysis and a case using Aesculus L. (Sapindaceae) including fossilsJOURNAL OF SYSTEMATICS EVOLUTION, Issue 5 2009A.J. HARRIS Abstract, We propose a simple statistical approach for using Dispersal,Vicariance Analysis (DIVA) software to infer biogeographic histories without fully bifurcating trees. In this approach, ancestral ranges are first optimized for a sample of Bayesian trees. The probability P of an ancestral range r at a node is then calculated as where Y is a node, and F(rY) is the frequency of range r among all the optimal solutions resulting from DIVA optimization at node Y, t is one of n topologies optimized, and Pt is the probability of topology t. Node Y is a hypothesized ancestor shared by a specific crown lineage and the sister of that lineage "x", where x may vary due to phylogenetic uncertainty (polytomies and nodes with posterior probability <100%). Using this method, the ancestral distribution at Y can be estimated to provide inference of the geographic origins of the specific crown group of interest. This approach takes into account phylogenetic uncertainty as well as uncertainty from DIVA optimization. It is an extension of the previously described method called Bayes-DIVA, which pairs Bayesian phylogenetic analysis with biogeographic analysis using DIVA. Further, we show that the probability P of an ancestral range at Y calculated using this method does not equate to pp*F(rY) on the Bayesian consensus tree when both variables are <100%, where pp is the posterior probability and F(rY) is the frequency of range r for the node containing the specific crown group. We tested our DIVA-Bayes approach using Aesculus L., which has major lineages unresolved as a polytomy. We inferred the most probable geographic origins of the five traditional sections of Aesculus and of Aesculus californica Nutt. and examined range subdivisions at parental nodes of these lineages. Additionally, we used the DIVA-Bayes data from Aesculus to quantify the effects on biogeographic inference of including two wildcard fossil taxa in phylogenetic analysis. Our analysis resolved the geographic ranges of the parental nodes of the lineages of Aesculus with moderate to high probabilities. The probabilities were greater than those estimated using the simple calculation of pp*F(ry) at a statistically significant level for two of the six lineages. We also found that adding fossil wildcard taxa in phylogenetic analysis generally increased P for ancestral ranges including the fossil's distribution area. The ,P was more dramatic for ranges that include the area of a wildcard fossil with a distribution area underrepresented among extant taxa. This indicates the importance of including fossils in biogeographic analysis. Exmination of range subdivision at the parental nodes revealed potential range evolution (extinction and dispersal events) along the stems of A. californica and sect. Parryana. [source] New molecular data for tardigrade phylogeny, with the erection of Paramacrobiotus gen. nov.JOURNAL OF ZOOLOGICAL SYSTEMATICS AND EVOLUTIONARY RESEARCH, Issue 4 2009R. Guidetti Abstract Up to few years ago, the phylogenies of tardigrade taxa have been investigated using morphological data, but relationships within and between many taxa are still unresolved. Our aim has been to verify those relationships adding molecular analysis to morphological analysis, using nearly complete 18S ribosomal DNA gene sequences (five new) of 19 species, as well as cytochrome oxidase subunit 1 (COI) mitochondrial DNA gene sequences (15 new) from 20 species, from a total of seven families. The 18S rDNA tree was calculated by minimum evolution, maximum parsimony (MP) and maximum likelihood (ML) analyses. DNA sequences coding for COI were translated to amino acid sequences and a tree was also calculated by neighbour-joining, MP and ML analyses. For both trees (18S rDNA and COI) posterior probabilities were calculated by MrBayes. Prominent findings are as follows: the molecular data on Echiniscidae (Heterotardigrada) are in line with the phylogenetic relationships identifiable by morphological analysis. Among Eutardigrada, orders Apochela and Parachela are confirmed as sister groups. Ramazzottius (Hypsibiidae) results more related to Macrobiotidae than to the genera here considered of Hypsibiidae. Macrobiotidae and Macrobiotus result not monophyletic and confirm morphological data on the presence of at least two large groups within Macrobiotus. Using 18S rDNA and COI mtDNA genes, a new phylogenetic line has been identified within Macrobiotus, corresponding to the ,richtersi-areolatus group'. Moreover, cryptic species have been identified within the Macrobiotus,richtersi group' and within Richtersius. Some evolutionary lines of tardigrades are confirmed, but others suggest taxonomic revision. In particular, the new genus Paramacrobiotus gen. n. has been identified, corresponding to the phylogenetic line represented by the ,richtersi-areolatus group'. Zusammenfassung Die Anzahl der Arten im Phylum Tardigrada ist in den letzten 25 Jahren von 500 Arten auf inzwischen fast 1000 Arten angestiegen. Zurzeit besteht die Gruppe aus zwei Klassen (Heterotardigrada und Eutardigrada), vier Ordnungen, 21 Familien, und 104 Gattungen. Trotz der Häufigkeit der Tardigraden wurde ihnen seit ihrer Entdeckung im Jahr 1773 nur wenig Aufmerksamkeit geschenkt. Bis vor wenigen Jahren wurden ausschließlich morphologische Merkmale verwendet, um die Phylogenie der Tardigrada zu untersuchen. Dennoch sind die Verhältnisse zwischen und innerhalb vieler Arten noch nicht eindeutig geklärt. Das Ziel der vorliegenden Arbeit war es, die bereits bekannten, morphologischen Verhältnisse mit molekularen Ergebnissen zu belegen. Hierzu wurden nur vollständige Sequenzen der ribosomalen 18S rDNA von 19 Arten verwendet. Fünf neue Sequenzen wurden dabei hinzugefügt. Weiterhin wurden von 15 Arten neue mitochrondriale COI Sequenzen verwendet, die mit fünf bekannten COI Sequenzen zu insgesamt sieben Familien gehören. Der 18S rDNA-Baum wurde durch ME, maximum parsimony (MP) and ML Analysen berechnet. Die für COI kodierenden Sequenzen wurden in Aminosäuren übersetzt und der Baum mit NJ, MP and ML Analysen berechnet. Für beide Bäume (18 rDNA und COI) wurden die Wahrscheinlichkeiten durch MrBayes ermittelt. Dabei ergab sich, dass molekulare Daten mit den morphologischen Untersuchungen bei den Echiniscidae (Heterotardigrada) übereinstimmen. Bei Eutardigrada wurden die Ordnungen Apochela und Parachela als Schwestergruppen bestätigt. Ramazzottius (Hypsibiidae) gehört zu der Familie Macrobiotidae und weniger zu Hypsibiidae, zu der die Gattung gegenwärtig gestellt wird. Die molekularen und morphologischen Daten deuten darauf hin, dass es mindestens zwei großer Gruppen innerhalb von Macrobiotus gibt. Durch die 18 rDNA und COI mtDNA Sequenzen konnte eine neue phylogenetische Linie innerhalb von Macrobiotus, der ,richtersi-areolatus Gruppe' zugehörig, identifiziert werden. Weiterhin sind kryptische Arten innerhalb der Macrobiotus richtersi Gruppe' und innerhalb von Richtersius gefunden worden. Die vorliegende Arbeit verifiziert die in vorangegangene Untersuchungen erarbeitete Phylogenie von Tardigraden. Es konnten einige Entwicklungslinien innerhalb den Tardigraden bestätigt werden, andere deuten zukünftige, taxonomische Revisionen an. So wurde die neue Gattung Paramacrobiotus eingeführt, entsprechend der phylogenetischen Linie, die bisher durch die ,richtersi-areolatus Gruppe' vertreten war. [source] Systematic position of the pelagic Thecosomata and Gymnosomata within Opisthobranchia (Mollusca, Gastropoda) , revival of the PteropodaJOURNAL OF ZOOLOGICAL SYSTEMATICS AND EVOLUTIONARY RESEARCH, Issue 2 2006A. Klussmann-Kolb Abstract The complete 18S (SSU) rRNA as well partial 28S (LSU) rRNA and partial mitochondrial COI sequences have been used to reconstruct the phylogenetic relationships within Opisthobranchia with special focus on the pelagic orders Thecosomata and Gymnosomata. Maximum parsimony, maximum likelihood, distance as well as Bayesian analysis of a combined dataset of the three genes reveals that Thecosomata and Gymnosomata are sister groups and together are closely related to Anaspidea. Possible sister taxon to Thecosomata, Gymnosomata and Anaspidea is Cephalaspidea s. str. Analysis of a taxon-extended dataset of partial 28S sequences supported a basal position of Limacina within Euthecosomata. Within Cavolinidae, Creseis is basal to the other taxa. Other phylogenetic implications from the present results are also discussed. Investigation of the morphology and histology of Thecosomata and Gymnosomata as well as several other opisthobranch taxa helped to identify autapomorphies for Thecosomata and Gymnosomata as well as apomorphies for the clades including these taxa. Zusammenfassung Auf Basis der kompletten 18S rRNA- und partiellen 28S rRNA- sowie partiellen COI- Sequenzen wurde die Phylogenie der Opisthobranchia unter besonderer Berücksichtigung der pelagischen Thecosomata und Gymnosomata rekonstruiert. Maximum Parsimonie-, Maximum Likelihood- sowie Distanz- Berechnungen und Bayes'sche Analysen zeigen, dass die Thecosomata und Gymnosomata Schwestergruppen und nah verwandt mit den Anaspidea sind. Die potentielle Schwestergruppe zu Thecosomata, Gymnosomata und Anaspidea sind die Cephalaspidea s. str. Die Analyse eines taxonerweiterten Datensatzes von partiellen 28S rRNA-Sequenzen unterstützt die basale Position von Limacina innerhalb der Euthecosomata. Innerhalb der Cavolinidae stellt Creseis das basalste Taxon dar. Weitere Schlussfolgerungen zu phylogenetischen Verwandtschaftsverhältnissen der Opisthobranchia auf Grundlage der vorliegenden Untersuchungen werden diskutiert. Die Untersuchungen der Morphologie und Histologie der Thecosomata und Gymnosomata sowie anderer Opisthobranchia ließen apomorphe Merkmale der Thecosomata und Gymnosomata sowie Apomorphien der Kladen, die diese beiden pelagischen Taxa enthalten, erkennen. [source] Pycnogonid affinities: a reviewJOURNAL OF ZOOLOGICAL SYSTEMATICS AND EVOLUTIONARY RESEARCH, Issue 1 2005J. A. Dunlop Abstract Early authors regarded Pycnogonida (sea spiders) either as aquatic arachnids, ,degraded' crustaceans or as some sort of intermediate form between the two. Subsequently, pycnogonids were either placed among the Chelicerata or considered as an isolated group, unrelated to other arthropods. The latter model is untenable under phylogenetic systematics and recent cladistic studies have supported one of two alternative hypotheses. The first is the traditional Chelicerata s.lat. concept, i.e. (Pycnogonida + Euchelicerata). This, however, has only one really convincing synapomorphy: chelate chelicerae. The second hypothesis recognizes (Pycnogonida + all other Euarthropoda) and has been recovered in various ,total evidence' studies. Morphologically some characters , the presence of gonopores on the trunk and absence of a labrum, nephridia and intersegmental tendons , support Cormogonida (Euarthropoda excluding pycnogonids). Advances in developmental biology have proposed clear interpretations of segmentation homologies. However, so far there is also a confrontation of the two hypotheses depending on whether the last walking leg segment is considered part of the prosoma. In this case pycnogonids have too many prosomal segments compared with Euchelicerata; perhaps implying they are not sister groups. Alternatively, if part of the postprosomal region, the last leg pair could correspond to the chilarial segment in euchelicerates and its uniramous state could be apomorphic with respect to other euarthropods. Molecular phylogenies need to be more rigorously analysed, better supported by data from different sources and technique-sensitive aspects need to be explored. Chelicerata s.lat. may emerge as the more convincing model, yet even the putative autapomorphy of chelicerae needs to be treated with caution as there are fossil ,great appendage' arthropods in the early Palaeozoic which also have a robust, food-gathering, pair of head limbs and which may lie on the chelicerate, or even the euarthropod, stem lineage. Zusammenfassung Frühere Autoren betrachteten die Pycnogonida (Asselspinnen) entweder als wasserbewohnende Spinnentiere oder als rückgebildete Krebstiere oder als eine Zwischenform zwischen den beiden Gruppen. Später wurden die Pycnogonida entweder den Chelicerata zugeordnet oder als eine isolierte Gruppe, die mit den anderen Arthropoden in keiner Verwandtschftsbeziehung steht, betrachtet. Die letztere Annahme ist unter den Aspekten der phylogenetischen Systematik unbrauchbar. Neue cladistische Untersuchungen unterstützen zwei verschiedene, alternative Hypothesen: die erste Hypothese entspricht dem traditionellen Chelicerata s. lat.-Konzept, d.h. Pycnogonida + Euchelicerata bilden eine Gruppe. Hier gibt es aber nur eine einzige überzeugende Synapomorphie: klauenartige Cheliceren. Die zweite Hypothese anerkennt eine Gruppierung (Pycnogonida + alle anderen Euarthropoda), entsprechend den Ergebnissen verschiedener ,,Total Evidence-Analysen''. Einige morphologische Merkmale, wie das Auftreten von Gonoporen am Rüssel, das Fehlen des Labrums, der Nephridien und der intersegmentalen Sehnen, unterstützt das Taxon Cormogonida (alle Euarthropoda mit Ausschluß der Pycnogonida). Fortschritte in der Entwicklungsbiologie erlauben jetzt eine klare Homologisierung der Segmente. Es besteht jedoch weiterhin ein Konflikt zwischen den beiden Hypothesen bezüglich der Frage, ob das letzte Laufbeinsegment ein Teil des Prosomas ist. In letzterem Fall hätten die Pycnogonida im Vergleich mit den Euchelicerata zu viele prosomale Segmente; vielleicht kann das als Hinweis angesehen werden, daß die beiden Taxa keine Schwestergruppen sind. Alternativ, wenn das letzte Laufbeinsegment ein Teil der post-prosomatischen Region ist, könnte es dem chilarialen Segment der Euchelicerata in seinem einstrahligen Zustand entsprechen und eine Apomorphie gegenüber den anderen Euarthropoden darstellen. Die molekularen Phylogeniestudien müssen strenger analysiert, besser durch Daten von anderer Seite unterstützt und die Aspekte der Empfindlichkeit der technischen Methoden besser untersucht werden. Das Chelicerata s. lat.- Modell mag als das mehr überzeugende erscheinen, doch müssen die vermutlichen Autoapomorphien der Chelicerata mit Vorsicht behandelt werden, denn es gibt da die fossilen Gliederfüßler aus dem frühen Paläozooikum, die sogenannten ,,great appendage'' - Euarthropoden mit einem großen robusten Paar von Kopfgliedern als Fangapparat, die nahe bei den Chelicerata stehend oder sogar als Stammgruppe der Euarthropoden angesehen werden können. [source] The origin of chalicotheres (Perissodactyla, Mammalia)PALAEONTOLOGY, Issue 6 2004J. J. Hooker Description of a new genus of perissodactyl, Protomoropus, for the species ,Hyracotherium'gabuniai Dashzeveg and its inclusion with a diversity of other primitive perissodactyls in a cladistic analysis results in the following higher order changes to our knowledge of perissodactyl phylogeny. Protomoropus is sister taxon to the Chalicotheriidae plus Lophiodontidae, which themselves are confirmed as sister groups. The previously monofamilial superfamily Chalicotherioidea is extended to include all three taxa. Paleomoropus and Lophiaspis are shown to be primitive lophiodontids. Various genera of the Isectolophidae are shown to be stem members of a clade that includes chalicotheres and lophiodonts. The infraorder Ancylopoda is extended to include them. Inclusion of isectolophids in the Ancylopoda rather than as stem tapiromorphs results in the break up of the clade Tapiromorpha. Instead, the modern perissodactyl groups, comprising the horse superfamily Equoidea and that of the rhinos and tapirs, the Ceratomorpha (here reduced in rank to parvorder), form a new clade which is here named infraorder Euperissodactyla nov. The Brontotheriidae form the sister group to Ancylopoda plus Euperissodactyla. The clade comprising Ancylopoda plus Euperissodactyla is named suborder Lophodontomorpha nov. The Chalicotherioidea and Chalicotheriidae evolved in Asia. The Lophiodontidae arose following dispersal from Asia to North America. Dispersal continued to Europe, where the family radiated. [source] Cladistic Analysis of A Problematic Ammonite Group: the Hamitidae (Cretaceous, Albian,turonian) and Proposals for New Cladistic TermsPALAEONTOLOGY, Issue 4 2002Neale MonksArticle first published online: 24 NOV 200 The Hamitidae are a family of mid,Cretaceous heteromorph ammonites including lineages leading to four other families. Problems are outlined in trying to describe the phylogeny of completely extinct groups such as these heteromorph ammonites using the existing cladistic terminology, which is largely concerned with extant taxa and their ancestors. To solve these problems, two new terms are proposed: ,crown groups and ,stem groups, which are equivalent to crown and stem groups in terms of the evolutionary history of a clade, but are not defined on the basis of extant taxa. Instead they are defined by the topology of the phylogenetic tree, the ,crown group being a clade defined by synapomorphies but which gave rise to no descendants. A ,stem group is a branch of a phylogenetic tree which comprises the immediate sister groups of a given ,crown group but is not itself a clade. Examples of these terms are described here with reference to the phylogeny of the Hamitidae and their descendants. The Hamitidae are paraphyletic and form ,stem groups to a number of ,crown groups, namely the Anisoceratidae, Baculitidae, Scaphitidae, and Turrilitidae. The definitions of the genera and subgenera are refined with respect to the type species and the clades within which they occur, and four new genera are described: Eohamites, Helicohamites, Sziveshamites, and Planohamites. [source] Conserved and convergent organization in the optic lobes of insects and isopods, with reference to other crustacean taxaTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 2 2003I. Sinakevitch Abstract The shared organization of three optic lobe neuropils,the lamina, medulla, and lobula,linked by chiasmata has been used to support arguments that insects and malacostracans are sister groups. However, in certain insects, the lobula is accompanied by a tectum-like fourth neuropil, the lobula plate, characterized by wide-field tangential neurons and linked to the medulla by uncrossed axons. The identification of a lobula plate in an isopod crustacean raises the question of whether the lobula plate of insects and isopods evolved convergently or are derived from a common ancestor. This question is here investigated by comparisons of insect and crustacean optic lobes. The basal branchiopod crustacean Triops has only two visual neuropils and no optic chiasma. This finding contrasts with the phyllocarid Nebalia pugettensis, a basal malacostracan whose lamina is linked by a chiasma to a medulla that is linked by a second chiasma to a retinotopic outswelling of the lateral protocerebrum, called the protolobula. In Nebalia, uncrossed axons from the medulla supply a minute fourth optic neuropil. Eumalacostracan crustaceans also possess two deep neuropils, one receiving crossed axons, the other uncrossed axons. However, in primitive insects, there is no separate fourth optic neuropil. Malacostracans and insects also differ in that the insect medulla comprises two nested neuropils separated by a layer of axons, called the Cuccati bundle. Comparisons suggest that neuroarchitectures of the lamina and medulla distal to the Cuccati bundle are equivalent to the eumalacostracan lamina and entire medulla. The occurrence of a second optic chiasma and protolobula are suggested to be synapomorphic for a malacostracan/insect clade. J. Comp. Neurol. 467:150,172, 2003. © 2003 Wiley-Liss, Inc. [source] A global phylogeny of apple snails: Gondwanan origin, generic relationships, and the influence of outgroup choice (Caenogastropoda: Ampullariidae)BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2009KENNETH A. HAYES Apple snails (Ampullariidae) are a diverse family of pantropical freshwater snails and an important evolutionary link to the common ancestor of the largest group of living gastropods, the Caenogastropoda. A clear understanding of relationships within the Ampullariidae, and identification of their sister taxon, is therefore important for interpreting gastropod evolution in general. Unfortunately, the overall pattern has been clouded by confused systematics within the family and equivocal results regarding the family's sister group relationships. To clarify the relationships among ampullariid genera and to evaluate the influence of including or excluding possible sister taxa, we used data from five genes, three nuclear and two mitochondrial, from representatives of all nine extant ampullariid genera, and species of Viviparidae, Cyclophoridae, and Campanilidae, to reconstruct the phylogeny of apple snails, and determine their affinities to these possible sister groups. The results obtained indicate that the Old and New World ampullariids are reciprocally monophyletic with probable Gondwanan origins. All four Old World genera, Afropomus, Saulea, Pila, and Lanistes, were recovered as monophyletic, but only Asolene, Felipponea, and Pomella were monophyletic among the five New World genera, with Marisa paraphyletic and Pomacea polyphyletic. Estimates of divergence times among New World taxa suggest that diversification began shortly after the separation of Africa and South America and has probably been influenced by hydrogeological events over the last 90 Myr. The sister group of the Ampullariidae remains unresolved, but analyses omitting certain outgroup taxa suggest the need for dense taxonomic sampling to increase phylogenetic accuracy within the ingroup. The results obtained also indicate that defining the sister group of the Ampullariidae and clarifying relationships among basal caenogastropods will require increased taxon sampling within these four families, and synthesis of both morphological and molecular data. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98, 61,76. [source] A molecular phylogeny of fleas (Insecta: Siphonaptera): origins and host associationsCLADISTICS, Issue 5 2008Michael F. Whiting Siphonaptera (fleas) is a highly specialized order of holometabolous insects comprising ,2500 species placed in 16 families. Despite a long history of extensive work on flea classification and biology, phylogenetic relationships among fleas are virtually unknown. We present the first formal analysis of flea relationships based on a molecular matrix of four loci (18S ribosomal DNA, 28S ribosomal DNA, Cytochrome Oxidase II, and Elongation Factor 1-alpha) for 128 flea taxa from around the world representing 16 families, 25 subfamilies, 26 tribes, and 83 flea genera with eight outgroups. Trees were reconstructed using direct optimization and maximum likelihood techniques. Our analysis supports Tungidae as the most basal flea lineage, sister group to the remainder of the extant fleas. Pygiopsyllomorpha is monophyletic, as are the constituent families Lycopsyllidae, Pygiopsyllidae, and Stivaliidae, with a sister group relationship between the latter two families. Macropsyllidae is resolved as sister group to Coptopsyllidae with moderate nodal support. Stephanociricidae is monophyletic, as are the two constituent subfamilies Stephanocircinae and Craneopsyllinae. Vermipsyllidae is placed as sister group to Jordanopsylla. Rhopalopsyllidae is monophyletic as are the two constituent subfamilies Rhopalopsyllinae and Parapsyllinae. Hystrichopsyllidae is paraphyletic with Hystrichopsyllini placed as sister to some species of Anomiopsyllini and Ctenopariini placed as sister to Carterettini. Ctenophthalmidae is grossly paraphyletic with the family broken into seven lineages dispersed on the tree. Most notably, Anomiopsyllini is paraphyletic. Pulicidae and Chimaeropsyllidae are both monophyletic and these families are sister groups. Ceratophyllomorpha is monophyletic and includes Ischnopsyllidae, Ceratophyllidae, and Leptopsyllidae. Leptopsyllidae is paraphyletic as are its constituent subfamilies Amphipsyllinae and Leptopsyllinae and the tribes Amphipsyllini and Leptopsyllini. Ischnopsyllidae is monophyletic. Ceratophyllidae is monophyletic, with a monophyletic Dactypsyllinae nested within Ceratophyllinae, rendering the latter group paraphyletic. Mapping of general host associations on our topology reveals an early association with mammals with four independent shifts to birds. © The Willi Hennig Society 2008. [source] Morphological data indicates two major clades of the subtribe Gorteriinae (Asteraceae-Arctotideae)CLADISTICS, Issue 3 2006Per Ola Karis The phylogeny of subtribe Gorteriinae (Asteraceae-Arctotideae) is investigated by means of cladistic analysis of morphological characters. Two sister groups are formed, namely a Gorteria clade also containing Hirpicium and Gazania, and a Berkheya clade, which also contains Cullumia, Cuspidia, Didelta and Heterorhachis. The Gorteria clade has strong jackknife support and is diagnosed by four morphological characters (leaves with longitudinally striate hairs, fringed anther apical appendages, pollen of the "Gazania -type", and subulate-ensiform, ascending style sweeping hairs) that are unique within the Asteraceae. The Berkheya clade is moderately supported and diagnosed by two characters without contradiction (spiny leaves, and mamillate, large style sweeping hairs). Hirpicium and Berkheya are paraphyletic, with the other, morphologically more homogeneous genera (Gorteria, and Gazania, Cullumia, Cuspidia, Didelta and Heterorhachis, respectively) nested within them. There is some evidence for a radiation of species of the summer rainfall area of South Africa and tropical Africa and the corresponding species are nested within a grade confined to the Cape Floristic Region. © The Willi Hennig Society 2006. [source] Gnathostomulid phylogeny inferred from a combined approach of four molecular loci and morphologyCLADISTICS, Issue 1 2006Martin V. Sørensen The phylogeny of the obscure metazoan phylum Gnathostomulida has previously only been addressed with cladistic analyses of morphological data. In the present study DNA sequence data from four molecular loci, including 18S rRNA, 28S rRNA, histone H3 and cytochrome c oxidase subunit I, are added to a revised morphological data matrix. The data set represents 23 gnathostomulid species that are analyzed under direct optimization using parsimony as the optimality criterion. The results obtained from analyzing the four molecular loci and combined morphological and molecular data under different parameter sets are generally very congruent, and differ only on minor points. The results clearly support gnathostomulid monophyly, as well as the basal division of Gnathostomulida into Filospermoidea and Bursovaginoidea. Filospermoidea were represented by species of Haplognathia and Cosmognathia, and generic monophyly is supported for both groups. Within Bursovaginoidea, Conophoralia (= Austrognathiidae) and Scleroperalia appear as sister groups. Monophyly of Mesognathariidae was confirmed as well, whereas the relationships between species of Gnathostomulidae and Onychognathiidae were contradicted by the molecular data when compared to morphological observations. ©The Willi Hennig Society 2006. [source] | ||||||||||||||||||||||