Phylogenetic Analysis (phylogenetic + analysis)

Distribution by Scientific Domains
Distribution within Life Sciences

Kinds of Phylogenetic Analysis

  • bayesian phylogenetic analysis
  • comparative phylogenetic analysis
  • comprehensive phylogenetic analysis
  • molecular phylogenetic analysis
  • new phylogenetic analysis
  • recent phylogenetic analysis

  • Terms modified by Phylogenetic Analysis

  • phylogenetic analysis shows

  • Selected Abstracts


    JOURNAL OF PHYCOLOGY, Issue 2 2006
    Nina Lundholm
    A study of 25 cultures tentatively identified as Pseudo-nitzschia delicatissima (Cleve) Heiden, and originating from geographically widely distributed locations, showed both morphological and genetic variation among strains. Use of rRNA-targeted DNA probes on 17 different strains showed large variation in the hybridization patterns. Detailed morphological studies placed the isolates into three groups. The sample on which the neotype of P. delicatissima is based was also examined, and used to establish the morphological identity of P. delicatissima. Phylogenetic analyses of 16 strains, based on sequences of internal transcriber spacer 1 (ITS1), 5.8S and ITS2 of the nuclear-encoded rDNA, supported the morphological observations and the hybridization studies, and revealed large genetic variation among strains. A combination of the morphological and molecular findings resulted in the description of two new species, P. decipiens sp. nov. and P. dolorosa sp. nov. P. dolorosa has a mixture of one or two rows of poroids in the striae whereas P. delicatissima always has two rows. In addition, P. dolorosa has wider valves and a lower density of poroids. P. decipiens differs from P. delicatissima by a higher density of striae on the valve face as well as a higher density of poroids on the girdle bands. Among the strains referred to P. delicatissima, an epitype was selected. Large genetic variation was found among the P. delicatissima strains and a subdivision into two major clades represent cryptic species. [source]


    EVOLUTION, Issue 9 2005
    Kenneth H. Kozak
    Abstract An important dimension of adaptive radiation is the degree to which diversification rates fluctuate or remain constant through time. Focusing on plethodontid salamanders of the genus Desmognathus, we present a novel synthetic analysis of phylogeographic history, rates of ecomorphological evolution and species accumulation, and community assembly in an adaptive radiation. Dusky salamanders are highly variable in life history, body size, and ecology, with many endemic lineages in the southern Appalachian Highlands of eastern North America. Our results show that lifehistory evolution had important consequences for the buildup of plethodontid-salamander species richness and phenotypic disparity in eastern North America, a global hot spot of salamander biodiversity. The origin of Desmognathus species with aquatic larvae was followed by a high rate of lineage accumulation, which then gradually decreased toward the present time. The peak period of lineage accumulation in the group coincides with evolutionary partitioning of lineages with aquatic larvae into seepage, stream-edge, and stream microhabitats. Phylogenetic simulations demonstrate a strong correlation between morphology and microhabitat ecology independent of phylogenetic effects and suggest that ecomorphological changes are concentrated early in the radiation of Desmognathus. Deep phylogeographic fragmentation within many codistributed ecomorph clades suggests long-term persistence of ecomorphological features and stability of endemic lineages and communities through multiple climatic cycles. Phylogenetic analyses of community structure show that ecomorphological divergence promotes the coexistence of lineages and that repeated, independent evolution of microhabitat-associated ecomorphs has a limited role in the evolutionary assembly of Desmognathus communities. Comparing and contrasting our results to other adaptive radiations having different biogeographic histories, our results suggest that rates of diversification during adaptive radiation are intimately linked to the degree to which community structure persists over evolutionary time. [source]


    EVOLUTION, Issue 5 2002
    Bernard J. Crespi
    Abstract The selective pressures involved in the evolution of semelparity and its associated life-history traits are largely unknown. We used species-level analyses, independent contrasts, and reconstruction of ancestral states to study the evolution of body length, fecundity, egg weight, gonadosomatic index, and parity (semelparity vs. degree of iteroparity) in females of 12 species of salmonid fishes. According to both species-level analysis and independent contrasts analysis, body length was positively correlated with fecundity, egg weight, and gonadosomatic index, and semelparous species exhibited a significantly steeper slope for the regression of egg weight on body length than did iteroparous species. Percent repeat breeding (degree of iteroparity) was negatively correlated with gonadosomatic index using independent contrasts analysis. Semelparous species had significantly larger eggs by species-level analysis, and the egg weight contrast for the branch on which semelparity was inferred to have originated was significantly larger than the other egg weight contrasts, corresponding to a remarkable increase in egg weight. Reconstruction of ancestral states showed that egg weight and body length apparently increased with the origin of semelparity, but fecundity and gonadosomatic index remained more or less constant or decreased. Thus, the strong evolutionary linkages between body size, fecundity, and gonadosomatic index were broken during the transition from iteroparity to semelparity. These findings suggest that long-distance migrations, which increase adult mortality between breeding episodes, may have been necessary for the origin of semelparity in Pacific salmon, but that increased egg weight, leading to increased juvenile survivorship, was crucial in driving the transition. Our analyses support the life-history hypotheses that a lower degree of repeat breeding is linked to higher reproductive investment per breeding episode, and that semelparity evolves under a combination of relatively high juvenile survivorship and relatively low adult survivorship. [source]


    JOURNAL OF PHYCOLOGY, Issue 3 2009
    Heroen Verbruggen
    The genus Pseudochlorodesmis (Bryopsidales) is composed of diminutive siphons of extreme morphological simplicity. The discovery of Pseudochlorodesmis -like juveniles in more complex Bryopsidales (e.g., the Halimeda microthallus stage) jeopardized the recognition of this genus. Confronted with this uncertainty, taxonomists transferred many simple siphons into a new genus, Siphonogramen. In this study, we used a multimarker approach to clarify the phylogenetic and taxonomic affinities of the Pseudochlorodesmis-Siphonogramen (PS) complex within the more morphologically complex bryopsidalean taxa. Our analyses reveal a new layer of diversity largely distinct from the lineages containing the structurally complex genera. The PS complex shows profound cryptic diversity exceeding the family level. We discuss a potential link between thallus complexity and the prevalence and profundity of cryptic diversity. For taxonomic simplicity and as a first step toward clarifying the taxonomy of these simple siphons, we propose to maintain Pseudochlorodesmis as a form genus and subsume Siphonogramen and Botryodesmis therein. [source]


    JOURNAL OF PHYCOLOGY, Issue 1 2004
    Allison J. Haywood
    Three new dinoflagellate species, Karenia papilionacea sp. nov., Karenia selliformis sp. nov., and Karenia bidigitata sp. nov., were compared with the toxic species Karenia mikimotoi (Miyake & Kominami ex Oda) G. Hansen & Moestrup, Karenia brevis (Davis) G. Hansen & Moestrup, and Karenia brevisulcata (Chang) G. Hansen & Moestrup using the same fixative. Distinguishing morphological characters for the genus Karenia included a smooth theca and a linear apical groove. The new species can be distinguished on the basis of morphological characters of vegetative cells that include the location and shape of the nucleus; the relative excavation of the hypotheca; the characteristics of apical and sulcal groove extensions on the epitheca; the cellular shape, size, and symmetry; the degree of dorsoventral compression; and the presence of an apical protrusion or carina. Species with pronounced dorsoventral compression swim in a distinctive fluttering motion. An intercingular tubular structure traversing the proximal and distal ends of the cingulum is common to the species of Karenia, Karlodinium micrum (Leadbeater & Dodge) J. Larsen, Gymnodinium pulchellum J. Larsen, and Gyrodinium corsicum Paulmier. Molecular phylogenetic analyses of rDNA sequence alignments show that the new species are phylogenetically distinct but closely related to K. mikimotoi and K. brevis. [source]


    N. Phillips
    Sargassum is one of the most species-rich genera in the brown algae with over 400 described species worldwide. The bulk of these species occurs in Pacific-Indian ocean waters with only a small portion found on the Atlantic side of the Isthmus of Panama. Sargassum also has one of the most subdivided and complex taxonomic systems used within the algae. Systematic distinctions within the genus are further complicated by high rates of phenotypic variability in several key morphological characters. Molecular analyses in such systems should allow testing of systematic concepts while providing insights into speciation and evolutionary patterns. Global molecular phylogenetic analyses using both conserved and variable regions of the Rubisco operon (rbcL and rbcL-IGS-rbcS) were performed with species from the Gulf of Mexico, Caribbean, and Pacific basin. Results confirm earlier analyses based on rbcL-IGS- rbcS from Pacific species at the subgeneric and sectional level while providing additional insights into the systematics and phylogenetics on a global scale. For example, species east of the Isthmus of Panama form a distinct well-resolved clade within the tropical subgenus. This result in sharp contrast to traditional systematic treatments but provides a window into the evolutionary history of this genus in the Pacific and Atlantic Ocean basins and a possible means to time speciation events. [source]

    Taxonomic Redescriptions of Two Ciliates, Protogastrostyla pulchra n. g., n. comb. and Hemigastrostyla enigmatica (Ciliophora: Spirotrichea, Stichotrichia), with Phylogenetic Analyses Based on 18S and 28S rRNA Gene Sequences

    ABSTRACT. The morphology and infraciliature of two stichotrichid ciliates, Gastrostyla pulchra(Perejaslawzewa 1886) Kahl, 1932 and Hemigastrostyla enigmatica(Dragesco and Dragesco-Kernéis 1986) Song & Wilbert, 1997, collected from marine and brackish sediments, were investigated by using living observations and protargol impregnations. Both 18S and 28S rRNA genes of these two species were sequenced. The 18S rDNA show high similarities (98.4%,99.7%) among populations of each species. There is about 94% similarity in 18S rDNA genes between G. pulchra and Gastrostyla steinii, the type species of the genus, which has been confirmed to be an oxytrichid by previous studies. In the phylogenetic trees of 18S, 28S, and combined 18S and 28S rDNA, both G. pulchra and H. enigmatica are consistently placed outside the well-established oxytrichid clade. Based on our analyses and previous ontogenetic data, we conclude that these two species may represent some lower groups in the subclass Stichotrichia, and that G. pulchra should represent a new genus, Protogastrostyla n. g. This new genus, which is morphologically similar to Gastrostyla, differs in its morphogenesis: the apical part of the old AZM is retained combining with the newly built membranelles that develop from the proter's oral primordium; the primary primordia of the dorsal kinety; and marginal primordia commence de novo without a definite contribution from the old structure. [source]

    A Fundamental Problem with Amino-Acid-Sequence Characters for Phylogenetic Analyses

    CLADISTICS, Issue 3 2000
    Mark P. Simmons
    Protein-coding genes may be analyzed in phylogenetic analyses using nucleotide-sequence characters and/or amino-acid-sequence characters. Although amino-acid-sequence characters "correct" for saturation (parallelism), amino-acid-sequence characters are subject to convergence and ignore phylogenetically informative variation. When all nucleotide-sequence characters have a consistency index of 1, characters coded using the amino acid sequence may have a consistency index of less than 1. The reason for this is that most amino acids are specified by more than one codon. If two different codons that both code for the same amino acid are derived independent of one another in divergent lineages, nucleotide-sequence characters may not be homoplasious when amino-acid-sequence characters may be homoplasious. Not only may amino-acid-sequence characters support groupings that are not supported by nucleotide-sequence characters, they may support contradictory groupings. Because this convergence is a problem of character delimitation, it affects the results of all tree-construction methods (maximum likelihood, neighbor joining, parsimony, etc.). In effect, coding amino-acid-sequence characters instead of nucleotide-sequence characters putatively corrects for saturation and definitely causes a convergence problem. An empirical example from the Mhc locus is given. [source]

    Introduction of a Nuclear Marker for Phylogenetic Analysis of Nepenthaceae

    PLANT BIOLOGY, Issue 6 2006
    H. Meimberg
    Abstract: Nepenthaceae, the pitcher plants of the Old World tropics show a remarkable diversity in SE Asia, especially on the islands of Borneo and Sumatra. This region is considered as a secondary center of diversity. Sequence analysis of the cpDNA trnK intron supports this hypothesis showing the species of the Malay Archipelago as neighbour group to the isolated species from Sri Lanka, the Seychelles, and Madagascar. Based on phylogenetic reconstructions an origin of recent Nepenthaceae in the Indian subcontinent is assumed. A recent investigation focused on a non-plastid, translocated copy of the trnK intron has revealed an incongruence to tree topology based on the cpDNA trnK intron. Although the translocated copy emerged as insufficient for phylogenetic reconstruction of Nepenthaceae some taxa showed, contrary to the cpDNA dataset, relatively high distances to the rest of the taxa. These results indicated that the phylogeny of the trnK intron could not reflect true phylogenetic relationships. We investigated the peptide transferase 1 (PTR1), to develop a phylogenetic marker that is based on a nuclear low copy gene in Nepenthes. All sequences obtained were probably functional, indicated by the ratio of point mutations of the single codon positions in exon and intron regions. Comparative analysis showed that this locus is of similar variability as the cpDNA trnK intron and, contrary to the translocated copy of trnK, potential useful for phylogenetic reconstruction. While in parts congruent to the plastid trnK intron phylogeny, a higher divergence of some sequences in PRT1 and in the previously reported, non cpDNA dataset indicates that remnants of an older species stock persisted east of Wallace's line and on the Sunda Shelf. This suggests that plastid haplotypes existing today in the main distribution center of the Nepenthaceae could be descendants of more recently dispersed lineages that had been transmitted to an old species stock. [source]

    New Phylogenetic Analysis of the Family Elephantidae Based on Cranial-Dental Morphology,

    Nancy E. Todd
    Abstract In 1973, Vincent Maglio published a seminal monograph on the evolution of the Elephantidae, in which he revised and condensed the 100+ species named by Henry Fairfield Osborn in 1931. Michel Beden further revised the African Elephantidae in 1979, but little systematic work has been done on the family since this publication. With addition of new specimens and species and revisions of chronology, a new analysis of the phylogeny and systematics of this family is warranted. A new, descriptive character dataset was generated from studies of modern elephants for use with fossil species. Parallel evolution in cranial and dental characters in all three lineages of elephants creates homoplastic noise in cladistic analysis, but new inferences about evolutionary relationships are possible. In this analysis, early Loxodonta and early African Mammuthus are virtually indistinguishable in dental morphology. The Elephas lineage is not monophyletic, and results from this analysis suggest multiple migration events out of Africa into Eurasia, and possibly back into Africa. New insight into the origin of the three lineages is also proposed, with Stegotetrabelodon leading to the Mammuthus lineage, and Primelephas as the ancestor of Loxodonta and Elephas. These new results suggest a much more complex picture of elephantid origins, evolution, and paleogeography. Anat Rec, 2010. © 2009 Wiley-Liss, Inc. [source]

    Phylogenetic Analysis of Complete rRNA Gene Sequence of Nosema philosamiae Isolated from the Lepidopteran Philosamia cynthia ricini

    ABSTRACT. The microsporidian Nosema philosamiae is a pathogen that infects the eri-silkworm Philosamia cynthia ricini. The complete sequence of rRNA gene (4,314 bp) was obtained by polymerase chain reaction amplification with specific primers and sequencing. The sequence analysis showed that the organization of the rRNA of N. philosamiae was similar to the pattern of Nosema bombycis. Phylogenetic analysis of rRNA gene sequences revealed that N. philosamiae had a close relationship with other Nosema species, confirming that N. philosamiae is correctly assigned to the genus Nosema. [source]

    Phylogenetic Analysis of Nosema antheraeae (Microsporidia) Isolated from Chinese Oak Silkworm, Antheraea pernyi

    ABSTRACT. The microsporidian Nosema antheraeae is a pathogen that infects the Chinese oak silkworm, Antheraea pernyi. We sequenced the complete small subunit (SSU) rRNA gene and the internal transcribed spacer (ITS) of N. antheraeae, and compared the SSU rRNA sequences in other microsporidia. The results indicated that Nosema species, including N. antheraeae, formed two distinct clades, consistent with previous observations. Furthermore, N. antheraeae is clustered with N. bombycis with high bootstrap support. The organization of the rRNA gene of N. antheraeae is LSU,ITS1,SSU,ITS2-5S, also following a pattern similar to the Nosema type species, N. bombycis. Thus, N. antheraeae is a Nosema species and has a close relationship to N. bombycis. [source]

    The Phylogenetic Handbook: A Practical Approach to Phylogenetic Analysis and Hypothesis Testing edited by LEMEY, P., SALEMI, M., and VANDAMME, A.-M.

    BIOMETRICS, Issue 1 2010
    Mike Steel
    No abstract is available for this article. [source]

    Escaping the matrix: a new algorithm for phylogenetic comparative studies of co-evolution

    CLADISTICS, Issue 4 2004
    Maggie Wojcicki
    An algorithm for generating host cladograms from parasite-host cladograms derived from parasite phylogenies, Phylogenetic Analysis for Comparing Trees (PACT), is described. PACT satisfies Assumption 0, that all the information in each parasite-host cladogram must be used in a co-evolutionary analysis, and that the host relationships depicted in the final host cladogram must be logically consistent with the phylogenetic relationships depicted in every part of every parasite-host cladogram used to construct the host cladogram. It accounts for cases of speciation by host switching and expansion of host range, and reticulated host relationships, in addition to co-speciation, sympatric speciation, and extinction in all input parasite-host cladograms, and does so without a priori weighting schemes and without a posteriori manipulation of the data. [source]

    Genetic diversity of endangered brown bear (Ursus arctos) populations at the crossroads of Europe, Asia and Africa

    Sébastien Calvignac
    Abstract Aim, Middle East brown bears (Ursus arctos syriacus Hemprich and Ehrenberg, 1828) are presently on the edge of extinction. However, little is known of their genetic diversity. This study investigates that question as well as that of Middle East brown bear relationships to surrounding populations of the species. Location, Middle East region of south-western Asia. Methods, We performed DNA analyses on 27 brown bear individuals. Twenty ancient bone samples (Late Pleistocene to 20th century) from natural populations and seven present-day samples obtained from captive individuals were analysed. Results, Phylogenetic analyses of the mitochondrial sequences obtained from seven ancient specimens identify three distinct maternal clades, all unrelated to one recently described from North Africa. Brown bears from Iran exhibit striking diversity (three individuals, three haplotypes) and form a unique clade that cannot be linked to any extant one. Individuals from Syria belong to the Holarctic clade now observed in Eastern Europe, Turkey, Japan and North America. Specimens from Lebanon surprisingly appear as tightly linked to the clade of brown bears now in Western Europe. Moreover, we show that U. a. syriacus in captivity still harbour haplotypes closely linked to those found in ancient individuals. Main conclusion, This study brings important new information on the genetic diversity of brown bear populations at the crossroads of Europe, Asia and Africa. It reveals a high level of diversity in Middle East brown bears and extends the historical distribution of the Western European clade to the East. Our analyses also suggest the value of a specific breeding programme for captive populations. [source]

    Electrophoretic analysis of sequence variability in three mitochondrial DNA regions for ascaridoid parasites of human and animal health significance

    ELECTROPHORESIS, Issue 13 2008
    Ming-Wei Li
    Abstract Sequence variability in three mitochondrial DNA (mtDNA) regions, namely cytochrome c oxidase subunit 1 (cox1), NADH dehydrogenase subunits 1 and 4 (nad1 and nad4), among and within Toxocara canis, T. cati, T. malaysiensis, T. vitulorum and Toxascaris leonina from different geographical origins was examined by a mutation-scanning approach. A portion of the cox1 gene (pcox1), a portion of the nad1 and nad4 genes (pnad1 and pnad4) were amplified separately from individual ascaridoid nematodes by polymerase chain reaction and the amplicons analyzed by single-strand conformation polymorphism (SSCP). Representative samples displaying sequence variation in SSCP profiles were subjected to sequencing in order to define genetic markers for their specific identification and differentiation. While the intra-specific sequence variations within each of the five ascaridoid species were 0.2,3.7% for pcox1, 0,2.8% for pnad1 and 0,2.3% for pnad4, the inter-specific sequence differences were significantly higher, being 7.9,12.9% for pcox1, 10.7,21.1% for pnad1 and 12.9,21.7% for pnad4, respectively. Phylogenetic analyses based on the combined sequences of pcox1, pnad1 and pnad4 revealed that the recently described species T. malaysiensis was more closely related to T. cati than to T. canis. These findings provided mtDNA evidence for the validity of T. malaysiensis and also demonstrated clearly the usefulness and attributes of the mutation-scanning sequencing approach for studying the population genetic structures of these and other nematodes of socio-economic importance. [source]

    Homologues of nitrite reductases in ammonia-oxidizing archaea: diversity and genomic context

    Rita Bartossek
    Summary Ammonia-oxidizing archaea are frequent and ubiquitous inhabitants of terrestrial and marine environments. As they have only recently been detected, most aspects of their metabolism are yet unknown. Here we report on the occurrence of genes encoding potential homologues of copper-dependent nitrite reductases (NirK) in ammonia-oxidizing archaea of soils and other environments using metagenomic approaches and PCR amplification. Two pairs of highly overlapping 40 kb genome fragments, each containing nirK genes of archaea, were isolated from a metagenomic soil library. Between 68% and 85% of the open reading frames on these genome fragments had homologues in the genomes of the marine archaeal ammonia oxidizers Nitrosopumilus maritimus and Cenarchaeum symbiosum. Extensions of NirK homologues with C-terminal fused amicyanin domains were deduced from two of the four fosmids indicating structural variation of these multicopper proteins in archaea. Phylogenetic analyses including all major groups of currently known NirK homologues revealed that the deduced protein sequences of marine and soil archaea were separated into two highly divergent lineages that did not contain bacterial homologues. In contrast, another separated lineage contained potential multicopper oxidases of both domains, archaea and bacteria. More nirK gene variants directly amplified by PCR from several environments indicated further diversity of the gene and a widespread occurrence in archaea. Transcription of the potential archaeal nirK in soil was demonstrated at different water contents, but no significant increase in transcript copy number was observed with increased denitrifying activity. [source]

    Widespread occurrence of an intranuclear bacterial parasite in vent and seep bathymodiolin mussels

    Frank U. Zielinski
    Summary Many parasitic bacteria live in the cytoplasm of multicellular animals, but only a few are known to regularly invade their nuclei. In this study, we describe the novel bacterial parasite "Candidatus Endonucleobacter bathymodioli" that invades the nuclei of deep-sea bathymodiolin mussels from hydrothermal vents and cold seeps. Bathymodiolin mussels are well known for their symbiotic associations with sulfur- and methane-oxidizing bacteria. In contrast, the parasitic bacteria of vent and seep animals have received little attention despite their potential importance for deep-sea ecosystems. We first discovered the intranuclear parasite "Ca. E. bathymodioli" in Bathymodiolus puteoserpentis from the Logatchev hydrothermal vent field on the Mid-Atlantic Ridge. Using primers and probes specific to "Ca. E. bathymodioli" we found this intranuclear parasite in at least six other bathymodiolin species from vents and seeps around the world. Fluorescence in situ hybridization and transmission electron microscopy analyses of the developmental cycle of "Ca. E. bathymodioli" showed that the infection of a nucleus begins with a single rod-shaped bacterium which grows to an unseptated filament of up to 20 ,m length and then divides repeatedly until the nucleus is filled with up to 80 000 bacteria. The greatly swollen nucleus destroys its host cell and the bacteria are released after the nuclear membrane bursts. Intriguingly, the only nuclei that were never infected by "Ca. E. bathymodioli" were those of the gill bacteriocytes. These cells contain the symbiotic sulfur- and methane-oxidizing bacteria, suggesting that the mussel symbionts can protect their host nuclei against the parasite. Phylogenetic analyses showed that the "Ca. E. bathymodioli" belongs to a monophyletic clade of Gammaproteobacteria associated with marine metazoans as diverse as sponges, corals, bivalves, gastropods, echinoderms, ascidians and fish. We hypothesize that many of the sequences from this clade originated from intranuclear bacteria, and that these are widespread in marine invertebrates. [source]

    Phylogenetic analyses of ribosomal DNA-containing bacterioplankton genome fragments from a 4000 m vertical profile in the North Pacific Subtropical Gyre

    Vinh D. Pham
    Summary High-throughput identification of rRNA gene-containing clones in large insert metagenomic libraries is difficult, because of the high background of host ribosomal RNA (rRNA) and rRNA genes. To address this challenge, a membrane hybridization method was developed to identify all bacterial small subunit rRNA-containing fosmid clones of microbial community DNA from seven different depths in the North Pacific Subtropical Gyre. Out of 101,376 clones screened, 751 rDNA-containing clones were identified that grouped in ,60 different clades. Several rare sequences only remotely related to known groups were detected, including a Wolbachia -related sequence containing a putative intron or intervening sequence, as well as seven sequences from Order Myxococcales not previously detected in pelagic habitats. Stratified, depth-specific population structure was evident within both cultured and uncultured lineages. Conversely, some eurybathyal members of the genera Alcanivorax and Rhizobium shared identical small subunit ribosomal DNA sequences that were distributed from surface waters to the 4000 m depth. Comparison with similar analyses in Monterey Bay microbial communities revealed previously recognized, as well as some distinctive, depth-stratified partitioning that distinguished coastal from open ocean bacterioplankton populations. While some bias was evident in fosmid clone recovery in a few particular lineages, the overall phylogenetic group recovery and distributions were consistent with previous studies, as well as with direct shotgun sequence data from the same source DNA. [source]

    Quantitative analyses of the abundance and composition of ammonia-oxidizing bacteria and ammonia-oxidizing archaea of a Chinese upland red soil under long-term fertilization practices

    Ji-zheng He
    Summary The abundance and composition of soil ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) were investigated by using quantitative real-time polymerase chain reaction, cloning and sequencing approaches based on amoA genes. The soil, classified as agri-udic ferrosols with pH (H2O) ranging from 3.7 to 6.0, was sampled in summer and winter from long-term field experimental plots which had received 16 years continuous fertilization treatments, including fallow (CK0), control without fertilizers (CK) and those with combinations of fertilizer nitrogen (N), phosphorus (P) and potassium (K): N, NP, NK, PK, NPK and NPK plus organic manure (OM). Population sizes of AOB and AOA changed greatly in response to the different fertilization treatments. The NPK + OM treatment had the highest copy numbers of AOB and AOA amoA genes among the treatments that received mineral fertilizers, whereas the lowest copy numbers were recorded in the N treatment. Ammonia-oxidizing archaea were more abundant than AOB in all the corresponding treatments, with AOA to AOB ratios ranging from 1.02 to 12.36. Significant positive correlations were observed among the population sizes of AOB and AOA, soil pH and potential nitrification rates, indicating that both AOB and AOA played an important role in ammonia oxidation in the soil. Phylogenetic analyses of the amoA gene fragments showed that all AOB sequences from different treatments were affiliated with Nitrosospira or Nitrosospira- like species and grouped into cluster 3, and little difference in AOB community composition was recorded among different treatments. All AOA sequences fell within cluster S (soil origin) and cluster M (marine and sediment origin). Cluster M dominated exclusively in the N, NP, NK and PK treatments, indicating a pronounced difference in the community composition of AOA in response to the long-term fertilization treatments. These findings could be fundamental to improve our understanding of the importance of both AOB and AOA in the cycling of nitrogen and other nutrients in terrestrial ecosystems. [source]

    Vertical distribution of picoeukaryotic diversity in the Sargasso Sea

    Fabrice Not
    Summary Eukaryotic molecular diversity within the picoplanktonic size-fraction has primarily been studied in marine surface waters. Here, the vertical distribution of picoeukaryotic diversity was investigated in the Sargasso Sea from euphotic to abyssal waters, using size-fractionated samples (< 2 ,m). 18S rRNA gene clone libraries were used to generate sequences from euphotic zone samples (deep chlorophyll maximum to the surface); the permanent thermocline (500 m); and the pelagic deep-sea (3000 m). Euphotic zone and deep-sea data contrasted strongly, the former displaying greater diversity at the first-rank taxon level, based on 232 nearly full-length sequences. Deep-sea sequences belonged almost exclusively to the Alveolata and Radiolaria, while surface samples also contained known and putative photosynthetic groups, such as unique Chlorarachniophyta and Chrysophyceae sequences. Phylogenetic analyses placed most Alveolata and Stramenopile sequences within previously reported ,environmental' clades, i.e. clades within the Novel Alveolate groups I and II (NAI and NAII), or the novel Marine Stramenopiles (MAST). However, some deep-sea NAII formed distinct, bootstrap supported clades. Stramenopiles were recovered from the euphotic zone only, although many MAST are reportedly heterotrophic, making the observed distribution a point for further investigation. An unexpectedly high proportion of radiolarian sequences were recovered. From these, five environmental radiolarian clades, RAD-I to RAD-V, were identified. RAD-IV and RAD-V were composed of Taxopodida-like sequences, with the former solely containing Sargasso Sea sequences, although from all depth zones sampled. Our findings highlight the vast diversity of these protists, most of which remain uncultured and of unknown ecological function. [source]

    Proteorhodopsin photosystem gene clusters exhibit co-evolutionary trends and shared ancestry among diverse marine microbial phyla

    Jay McCarren
    Summary Since the recent discovery of retinylidene proteins in marine bacteria (proteorhodopsins), the estimated abundance and diversity of this gene family has expanded rapidly. To explore proteorhodopsin photosystem evolutionary and distributional trends, we identified and compared 16 different proteorhodopsin-containing genome fragments recovered from naturally occurring bacterioplankton populations. In addition to finding several deep-branching proteorhodopsin sequences, proteorhodopsins were found in novel taxonomic contexts, including a betaproteobacterium and a planctomycete. Approximately one-third of the proteorhodopsin-containing genome fragments analysed, as well as a number of recently reported marine bacterial whole genome sequences, contained a linked set of genes required for biosynthesis of the rhodopsin chromophore, retinal. Phylogenetic analyses of the retinal biosynthetic genes suggested their co-evolution and probable coordinated lateral gene transfer into disparate lineages, including Euryarchaeota, Planctomycetales, and three different proteobacterial lineages. The lateral transfer and retention of genes required to assemble a functional proteorhodopsin photosystem appears to be a coordinated and relatively frequent evolutionary event. Strong selection pressure apparently acts to preserve these light-dependent photosystems in diverse marine microbial lineages. [source]

    Microbiological investigation of methane- and hydrocarbon-discharging mud volcanoes in the Carpathian Mountains, Romania

    Karine Alain
    Summary Paclele Mici is a terrestrial mud volcano field located in the Carpathian Mountains (Romania), where thermal alteration of sedimentary organic compounds leads to methane, higher hydrocarbons and other petroleum compounds that are continuously released into the environment. The hydrocarbons represent potential substrates for microorganisms. We studied lipid biomarkers, stable isotope ratios, the effect of substrate (methane, other organic compounds) addition and 16S rRNA genes to gain insights into the hitherto unknown microbial community at this site. Quantitative real-time polymerase chain reaction analysis demonstrated that bacteria were much more abundant than archaea. Phylogenetic analyses of 16S rDNA clone sequences indicated the presence of bacterial and archaeal lineages generally associated with the methane cycle (methanogens, aerobic and anaerobic methanotrophs), the sulfur cycle (sulfate reducers), and groups linked to the anaerobic degradation of alkanes or aromatic hydrocarbons. The presence of sulfate reducers, methanogens and methanotrophs in this habitat was also confirmed by concurrent surveys of lipid biomarkers and their isotopic signatures. Incubation experiments with several common and complex substrates revealed the potential of the indigenous microbial community for sulfate reduction, methanogenesis and aerobic methanotrophy. Additionally, consistently to the detection of methane-oxidizing archaea (ANME) and 13C-depleted archaeal lipids, a weak but significant activity of anaerobic methane oxidation was measured by radiotracer techniques and in vitro. This survey is the first to report the presence and activity of ANME in a terrestrial environment. [source]

    Microsite-dependent changes in methanogenic populations in a boreal oligotrophic fen

    Pierre E. Galand
    Summary Wetlands, including peatlands, are the main source of natural methane emission. Well-defined fen microsites have different methane emissions rates, but it is not known whether the methane-producing Archaea communities vary at these sites. Possible horizontal variations of communities, in a natural oligotrophic fen, were analysed by characterizing the methanogens from two well-defined microsites: Eriophorum lawn and Hummock. Community structures were studied at two different layers of the fen, showing, respectively, high and low methane production. The structure of methanogen populations was determined using molecular techniques targeting the 16SrRNA gene and combined denaturing gradient gel electrophoresis (DGGE) and restriction fragment length polymorphism (RFLP) analysis. Results subjected to non-metric multidimensional scaling (MDS), diversity indices calculation and phylogenetic analysis revealed that upper layer communities changed with site while deeper layer communities remained the same. Phylogenetic analyses revealed six different clusters of sequences grouping with only two known orders of methanogens. Upper layers of Hummock were dominated by sequences clustering with members of Methanomicrobiales and sequences dominating the upper part of the Eriophorum lawn were related to members of the order Methanosarcinales. Novel methanogenic sequences were found at both sites at both depths. Vegetation characterizing the microsites probably influences the microbial communities in the layers of the fen where methane is produced. [source]


    EVOLUTION, Issue 6 2008
    Pascal L. Zaffarano
    Agriculture played a significant role in increasing the number of pathogen species and in expanding their geographic range during the last 10,000 years. We tested the hypothesis that a fungal pathogen of cereals and grasses emerged at the time of domestication of cereals in the Fertile Crescent and subsequently speciated after adaptation to its hosts. Rhynchosporium secalis, originally described from rye, causes an important disease on barley called scald, although it also infects other species of Hordeum and Agropyron. Phylogenetic analyses based on four DNA sequence loci identified three host-associated lineages that were confirmed by cross-pathogenicity tests. Bayesian analyses of divergence time suggested that the three lineages emerged between ,1200 to 3600 years before present (B.P.) with a 95% highest posterior density ranging from 100 to 12,000 years B.P. depending on the implemented clock models. The coalescent inference of demographic history revealed a very recent population expansion for all three pathogens. We propose that Rhynchosporium on barley, rye, and Agropyron host species represent three cryptic pathogen species that underwent independent evolution and ecological divergence by host-specialization. We postulate that the recent emergence of these pathogens followed host shifts. The subsequent population expansions followed the expansion of the cultivated host populations and accompanying expansion of the weedy Agropyron spp. found in fields of cultivated cereals. Hence, agriculture played a major role in the emergence of the scald diseases, the adaptation of the pathogens to new hosts and their worldwide dissemination. [source]


    EVOLUTION, Issue 3 2008
    Justin Ramsey
    Adaptive evolution is often associated with speciation. In plants, however, ecotypic differentiation is common within widespread species, suggesting that climatic and edaphic specialization can outpace cladogenesis and the evolution of postzygotic reproductive isolation. We used cpDNA sequence (5 noncoding regions, 3.5 kb) and amplified fragment length polymorphisms (AFLPs: 4 primer pairs, 1013 loci) to evaluate the history of ecological differentiation in the North American Achillea millefolium, an autopolyploid complex of "ecological races" exhibiting morphological, physiological, and life-history adaptations to diverse environments. Phylogenetic analyses reveal North American A. millefolium to be a monophyletic group distinct from its European and Asian relatives. Based on patterns of sequence divergence, as well as fossil and paleoecological data, colonization of North America appears to have occurred via the Bering Land Bridge during the Pleistocene (1.8 MYA to 11,500 years ago). Population genetic analyses indicate negligible structure within North American A. millefolium associated with varietal identity, geographic distribution, or ploidy level. North American populations, moreover, exhibit the signature of demographic expansion. These results affirm the "ecotype" concept of the North American Achillea advocated by classical research and demonstrate the rapid rate of ecological differentiation that sometimes occurs in plants. [source]


    EVOLUTION, Issue 9 2005
    Kenneth H. Kozak
    Abstract An important dimension of adaptive radiation is the degree to which diversification rates fluctuate or remain constant through time. Focusing on plethodontid salamanders of the genus Desmognathus, we present a novel synthetic analysis of phylogeographic history, rates of ecomorphological evolution and species accumulation, and community assembly in an adaptive radiation. Dusky salamanders are highly variable in life history, body size, and ecology, with many endemic lineages in the southern Appalachian Highlands of eastern North America. Our results show that lifehistory evolution had important consequences for the buildup of plethodontid-salamander species richness and phenotypic disparity in eastern North America, a global hot spot of salamander biodiversity. The origin of Desmognathus species with aquatic larvae was followed by a high rate of lineage accumulation, which then gradually decreased toward the present time. The peak period of lineage accumulation in the group coincides with evolutionary partitioning of lineages with aquatic larvae into seepage, stream-edge, and stream microhabitats. Phylogenetic simulations demonstrate a strong correlation between morphology and microhabitat ecology independent of phylogenetic effects and suggest that ecomorphological changes are concentrated early in the radiation of Desmognathus. Deep phylogeographic fragmentation within many codistributed ecomorph clades suggests long-term persistence of ecomorphological features and stability of endemic lineages and communities through multiple climatic cycles. Phylogenetic analyses of community structure show that ecomorphological divergence promotes the coexistence of lineages and that repeated, independent evolution of microhabitat-associated ecomorphs has a limited role in the evolutionary assembly of Desmognathus communities. Comparing and contrasting our results to other adaptive radiations having different biogeographic histories, our results suggest that rates of diversification during adaptive radiation are intimately linked to the degree to which community structure persists over evolutionary time. [source]


    EVOLUTION, Issue 3 2002
    Neil Davies
    Abstract Mitochondrial DNA and allozyme variation was examined in populations of two Neotropical butterflies, Heliconius charithonia and Dryas iulia. On the mainland, both species showed evidence of considerable gene flow over huge distances. The island populations, however, revealed significant genetic divergence across some, but not all, ocean passages. Despite the phylogenetic relatedness and broadly similar ecologies of these two butterflies, their intraspecific biogeography clearly differed. Phylogenetic analyses of mitochondrial DNA sequences revealed that populations of D. iulia north of St. Vincent are monophyletic and were probably derived from South America. By contrast, the Jamaican subspecies of H. charithonia rendered West Indian H. charithonia polyphyletic with respect to the mainland populations; thus, H. charithonia seems to have colonized the Greater Antilles on at least two separate occasions from Central America. Colonization velocity does not correlate with subsequent levels of gene flow in either species. Even where range expansion seems to have been instantaneous on a geological timescale, significant allele frequency differences at allozyme loci demonstrate that gene flow is severely curtailed across narrow ocean passages. Stochastic extinction, rapid (re)colonization, but low gene flow probably explain why, in the same species, some islands support genetically distinct and nonexpanding populations, while nearby a single lineage is distributed across several islands. Despite the differences, some common biogeographic patterns were evident between these butterflies and other West Indian taxa; such congruence suggests that intraspecific evolution in the West Indies has been somewhat constrained by earth history events, such as changes in sea level. [source]

    Phylogenetic distribution of microRNAs supports the basal position of acoel flatworms and the polyphyly of Platyhelminthes

    Lorenzo F. Sempere
    SUMMARY Phylogenetic analyses based on gene sequences suggest that acoel flatworms are not members of the phylum Platyhelminthes, but instead are the most basal branch of triploblastic bilaterians. Nonetheless, this result has been called into question. An alternative test is to use qualitative molecular markers that should, in principle, exclude the possibility of convergent (homoplastic) evolution in unrelated groups. microRNAs (miRNAs), noncoding regulatory RNA molecules that are under intense stabilizing selection, are a newly discovered set of phylogenetic markers that can resolve such taxonomic disputes. The acoel Childia sp. has recently been shown to possess a subset of the conserved core of miRNAs found across deuterostomes and protostomes, whereas a polyclad flatworm,in addition to this core subset,possesses miRNAs restricted to just protostomes. Here, we examine another acoel, Symsagittifera roscoffensis, and three other platyhelminths. Our results show that the distribution of miRNAs in S. roscoffensis parallels that of Childia. In addition, two of 13 new miRNAs cloned from a triclad flatworm are also found in other lophotrochozoan protostomes, but not in ecdysozoans, deuterostomes, or in basal metazoans including acoels. The limited set of miRNAs found in acoels, intermediate between the even more reduced set in cnidarians and the larger and expanding set in the rest of bilaterians, is compelling evidence for the basal position of acoel flatworms and the polyphyly of Platyhelminthes. [source]

    Complete subunit sequences, structure and evolution of the 6 × 6-mer hemocyanin from the common house centipede, Scutigera coleoptrata

    FEBS JOURNAL, Issue 13 2003
    Kristina Kusche
    Hemocyanins are large oligomeric copper-containing proteins that serve for the transport of oxygen in many arthropod species. While studied in detail in the Chelicerata and Crustacea, hemocyanins had long been considered unnecessary in the Myriapoda. Here we report the complete molecular structure of the hemocyanin from the common house centipede Scutigera coleoptrata (Myriapoda: Chilopoda), as deduced from 2D-gel electrophoresis, MALDI-TOF mass spectrometry, protein and cDNA sequencing, and homology modeling. This is the first myriapod hemocyanin to be fully sequenced, and allows the investigation of hemocyanin structure,function relationship and evolution. S. coleoptrata hemocyanin is a 6 × 6-mer composed of four distinct subunit types that occur in an approximate 2 : 2 : 1 : 1 ratio and are 49.5,55.5% identical. The cDNA of a fifth, highly diverged, putative hemocyanin was identified that is not included in the native 6 × 6-mer hemocyanin. Phylogenetic analyses show that myriapod hemocyanins are monophyletic, but at least three distinct subunit types evolved before the separation of the Chilopoda and Diplopoda more than 420 million years ago. In contrast to the situation in the Crustacea and Chelicerata, the substitution rates among the myriapod hemocyanin subunits are highly variable. Phylogenetic analyses do not support a common clade of Myriapoda and Hexapoda, whereas there is evidence in favor of monophyletic Mandibulata. [source]