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PubMed2005

Phylogenetic relationships and biogeography of Podarcis species from the Balkan Peninsula, by bayesian and maximum likelihood analyses of mitochondrial DNA sequences.

Wall lizards of the genus Podarcis (Sauria, Lacertidae) comprise 17 currently recognized species in southern Europe, where they are the predominant nonavian reptile group. The taxonomy of Podarcis is complex and unstable. Based on DNA sequence data, the species of Podarcis falls into four main groups that have substantial geographic coherence (Western island group, southwestern group, Italian group, and Balkan Peninsula group). The Balkan Peninsula species are divided into two subgroups: the subgroup of P. taurica (P. taurica, P. milensis, P. gaigeae, and perhaps P. melisellensis), and the subgroup of P. erhardii (P. erhardii and P. peloponnesiaca). In the present study, the question of phylogenetic relationships among the species of Podarcis encountered in the Balkan Peninsula was addressed using partial mtDNA sequences for cytochrome b (cyt b) and 16S rRNA (16S). The data support the monophyly of Podarcis and suggest that there are three phylogenetic clades: the clade A (P. taurica, P. gaigeae, P. milensis, and P. melisellensis); the clade B (P. erhardii and P. peloponnesiaca), and the clade C (P. muralis and P. sicula). By examining intraspecific relationships it was found that extant populations of P. erhardii are paraphyletic. Furthermore, subspecies previously defined on the basis of morphological characteristics do not correspond to different molecular phylogenetic clades, suggesting that their status should be reconsidered. The distinct geographic distribution of the major clades of the phylogenetic tree and its topology suggest a spatial and temporal sequence of phylogenetic separations that coincide with some major paleogeographic separations during the geological history of the Aegean Sea. The results stress the need for a reconsideration of the evolutionary history of Balkan Podarcis species and help overcome difficulties that classical taxonomy has encountered at both the species and subspecies level.

Albania↗

PubMed2006

Studies of morphological and molecular phylogenetic divergence in spiders (Araneae: Homalonychus) from the American southwest, including divergence along the Baja California Peninsula.

Comparative phylogenetic and phylogeographic analyses have revealed a pervasive midpeninsular divergence in the mitochondrial genealogies of numerous vertebrate taxa distributed on the Baja California Peninsula. In this study, we extend the investigation of regional vicariance in Baja California to an arthropod taxon by examining patterns of phylogenetic and morphological divergence in the spider genus Homalonychus (Araneae, Homalonychidae). We analyzed data from two mtDNA genes (16S rRNA and NADH dehydrogenase subunit (1) and a nuclear gene (28S rRNA) using maximum parsimony and Bayesian phylogenetic analyses, and also conducted geometric morphometric analyses employing landmark data on male and female genitalia. Genes and morphology both reveal a deep split across the Colorado River and Gulf of California, separating Homalonychus selenopoides on the east side of river from its congener Homalonychus theologus on the west side of the river, including the Baja California Peninsula. Along the north-south axis of the Baja Peninsula, an apparently more recent midpeninsular phylogenetic break is evident within H. theologus in the mitochondrial genome and in female genitalia. However, there is no measurable divergence between northern and southern populations in either nuclear DNA or male genitalia. We suggest that this discordance between datasets reflects either a difference in rates of evolution between male versus female systems, or that male-based nuclear gene flow is obscuring a phylogenetic split that is fixed in the female-based systems. Our findings provide additional support for a midpeninsular Baja divergence event, although the timing and geological evidence for such an event remain elusive.

Animals↗

PubMed2003

Functional and phylogenetic implications of molar flare variation in Miocene hominoids.

Comparative analyses of molar shape figure prominently in Miocene hominoid evolutionary studies, and incomplete understanding of functional and phylogenetic influences on molar shape variation can have direct consequences for the interpretation of fossil taxa. Molar flare is a shape trait whose polarity, phylogenetic distribution, and functional significance have been sources of contention. To clarify the determinants of molar flare variation in the hominoid radiation, a combination of statistical methods was employed to investigate the effects of diet, phylogeny, and geologic age upon several measures of molar shape, to identify interactions among these factors, and to estimate their relative influence. Classic indices of molar crown shape and cusp relief are highly significantly associated with diet and show no clear phylogenetic or temporal patterning. Correlations with diet are insignificant when phylogenetic effects are controlled, a result which is interpreted as an artifact of the distribution of folivory in the Miocene hominoid radiation. Possession of pronounced molar flare was found to be the primitive condition for Miocene hominoids, but molar flare reduction cannot be considered a crown hominoid synapomorphy. Molar flare is strongly correlated with geologic age but differs significantly among dietary categories when the effects of time are controlled. Among contemporaneous taxa, hard-object feeders consistently show the highest levels of flare. Molar flare reduction is hypothesized to arise from realignment of cusp positions to maximize molar shearing and increase working occlusal surface area, while variation in flare among contemporaneous taxa may be due, at least in part, to enamel thickness variation. The pronounced molar flare of Otavipithecus is interpreted as a primitive retention, although alternative dietary and phylogenetic interpretations cannot be excluded. A dramatic reversal of molar flare reduction in Mio-Pliocene hominins is interpreted as a synapomorphy of the crown hominin clade, thus supporting the hominin status of the Lukeino hominine. The last common ancestor of the Pan-Homo clade is predicted to have possessed relatively non-flaring molars, and implications of this hypothesis for early hominin recognition are discussed.

Anatomy, Comparative↗

PubMed2000

The use of phylogenetic data to develop molecular tools for the detection and genotyping of Yam mosaic virus. Potential application in molecular epidemiology.

Molecular detection of Yam mosaic virus (YMV), the most important potyvirus for yam plants (Dioscorea spp.) has been limited by its high genetic diversity. According to recent phylogenetic data, suitable molecular tools were developed for detection and genotyping. A reliable and rapid molecular test is described using single-tube immunocapture (IC)-RT-PCR combining the use of a monoclonal antibody able to recognise all YMV serotypes and primers designed to take into account the whole variability of YMV. Phylogenetic data were then used to develop an uncoupled IC-RT-PCR procedure adapted to the genotyping of the three major phylogenetic groups and the two recombinants implicated in the YMV epidemics in the Caribbean and French Guiana. A third exploitation of phylogenetic data was carried out with the development of a typing test based on the analysis of short nucleotide sequences. The direct sequencing of a 450 nts fragment constituted a reliable complementary typing tool as the resulting information was quite similar to that obtained with sequences of the complete coat protein gene. The approach, consisting in a robust study of YMV variability followed by the use of phylogenetic data to develop reliable detection and genotyping tools, offers new perspectives for powerful molecular epidemiological studies.

Enzyme-Linked Immunosorbent Assay↗

PubMed1998

Phylogenetic and physiological diversity of sulphate-reducing bacteria isolated from a salt marsh sediment.

The phylogenetic and physiological diversity of sulphate-reducing bacteria inhabiting a salt marsh rhizosphere were investigated. Sulphate-reducing bacteria were isolated from a salt marsh rhizosphere using enrichment cultures with electron donors thought to be prevalent in the rhizosphere of Spartina alterniflora. The relationship between phylogeny and nutritional characteristics of 10 strains was investigated. None of the isolates had 16S rRNA sequences identical to other delta subclass sulphate-reducers, sharing 85.3 to 98.1% sequence similarity with 16S rRNA sequences of their respective closest relatives. Phylogenetic analysis placed two isolates, obtained with ethanol as an electron donor, within the Desulfovibrionaceae. Seven isolates, obtained with acetate, butyrate, propionate, or benzoate, were placed within the Desulfobacteriaceae. One isolate, obtained with butyrate, fell within the Desulfobulbus assemblage, which is currently considered part of the Desulfobacteriaceae family. However, due to the phylogenetic breadth and physiological traits of this group, we propose that it be considered a new family, the "Desulfobulbusaceae." The isolates utilised an array of electron donors similar to their closest relatives with a few exceptions. As a whole, the phylogenetic and physiological data indicate isolation of several sulphate-reducing bacteria which might be considered as new species and representative of new genera. Comparison of the Desulfobacteriaceae isolates' 16S rRNA sequences to environmental clones originating from the same study site revealed that none shared more than 86% sequence similarity. The results provide further insight into the diversity of sulphate-reducing bacteria inhabiting the salt marsh ecosystem, as well as supporting general trends in the phylogenetic coherence of physiological traits of delta Proteobacteria sulphate reducers.

Base Sequence↗

PubMed2003

Phylogenetic relationships among Bactrocera species (Diptera: Tephritidae) inferred from mitochondrial DNA sequences.

Several members of the dipteran family Tephritdae are serious pests because females lay eggs in ripening fruit. The genus Bactrocera is one of the largest within the family with over 500 described species arranged in 28 subgenera. The phylogenetic relationships among the various species and subgenera, and the monophyly of specific groups have not been examined using a rigorous phylogenetic analysis. Therefore, phylogenetic relationships among 24 Bactrocera species belonging to 9 subgenera were inferred from DNA sequence of portions of the mitochondrial 16S rRNA, cytochrome oxidase II, tRNA(Lys), and tRNA(Asp) genes. Two morphological characters that traditionally have been used to define the four groups within the subgenus Bactrocera were evaluated in a phylogenetic context by mapping the character states onto the parsimony tree. In addition, the evolutionary trend in male-lure response was evaluated in a phylogenetic context. Maximum parsimony analyses suggested the following relationships: (1) the genus Bactrocera is monophyletic, (2) the subgenus B. (Zeugodacus) is paraphyletic, (3) the subgenus B. (Daculus) is a sister group to subgenus B. (Bactrocera), and (4) the subgenus B. (Bactrocera) is monophyletic. The mapping analyses suggested that the morphological characters exhibit a simple evolutionary transition from one character state to another. Male-lure response was identified as being a labile behavior that has been lost on multiple occasions. Cue-lure response was plesiomorphic to methyl-eugenol response, and the latter has evolved independently within the Bactrocera and Zeugodacus groups of subgenera. The implications of our results for devising a coherent, consolidated classification for Bactrocera is discussed.

Animals↗

PubMed2003

Phylogenetic utility of the second intron of LEAFY in Neillia and Stephanandra (Rosaceae) and implications for the origin of Stephanandra.

A homeotic gene, LEAFY, has been suggested to be a single-copy gene in diploid angiosperms. Nucleotide sequences of the second intron of this gene, along with those of several regions of the chloroplast genome (trnL-trnF, trnD-trnY-trnE-trnT, and matK-trnK) and nuclear ribosomal ITS, were obtained from the species of Neillia and Stephanandra to examine the phylogenetic utility of the intron and to elucidate the phylogenetic relationships among species of the two genera. PCR amplification of the second intron of LEAFY using universal degenerate primers produced PCR products in sufficient quantity for successful direct sequencing. The length of the intron ranged from 591 to 622 base pairs (bp) in Neillia and Stephanandra, except in N. thibetica (ca. 1370 bp), and sequence analysis of this region from multiple accessions revealed low levels of infraspecific variation. Comparison of the LEAFY data with ITS and cpDNA data demonstrated that the LEAFY intron was the most variable and useful for phylogenetic analysis at the species level, providing many more phylogenetically informative characters per 100 bp (7.4) than either ITS (3.2) or cpDNA (0.7). Phylogenetic analyses of LEAFY data using both maximum parsimony and likelihood methods generated well supported and highly resolved gene trees with few homoplasies (CI=0.97). Stephanandra is monophyletic and is nested within Neillia in both LEAFY and cpDNA trees, while the relationship is poorly resolved by ITS data. LEAFY and cpDNA data, however, strongly conflicted with each other with respect to the position of Stephanandra: LEAFY trees placed Stephanandra as sister to the ((N. affinis, N. gracilis), N. thyrsiflora) clade whereas cpDNA data suggested Stephanandra is sister to N. uekii. Both gene trees, however, are nearly identical to each other when Stephanandra is excluded. A hybrid origin of Stephanandra is suggested as a plausible hypothesis to explain the incongruence between LEAFY and cpDNA data sets, though gene duplication/loss and lineage sorting events cannot be ruled out as possibilities.

Amino Acid Sequence↗

PubMed2003

A new phylogenetic marker, apolipoprotein B, provides compelling evidence for eutherian relationships.

Higher-level relationships within, and the root of Placentalia, remain contentious issues. Resolution of the placental tree is important to the choice of mammalian genome projects and model organisms, as well as for understanding the biogeography of the eutherian radiation. We present phylogenetic analyses of 63 species representing all extant eutherian mammal orders for a new molecular phylogenetic marker, a 1.3kb portion of exon 26 of the apolipoprotein B (APOB) gene. In addition, we analyzed a multigene concatenation that included APOB sequences and a previously published data set (Murphy et al., 2001b) of three mitochondrial and 19 nuclear genes, resulting in an alignment of over 17kb for 42 placentals and two marsupials. Due to computational difficulties, previous maximum likelihood analyses of large, multigene concatenations for placental mammals have used quartet puzzling, less complex models of sequence evolution, or phylogenetic constraints to approximate a full maximum likelihood bootstrap. Here, we utilize a Unix load sharing facility to perform maximum likelihood bootstrap analyses for both the APOB and concatenated data sets with a GTR+Gamma+I model of sequence evolution, tree-bisection and reconnection branch-swapping, and no phylogenetic constraints. Maximum likelihood and Bayesian analyses of both data sets provide support for the superordinal clades Boreoeutheria, Euarchontoglires, Laurasiatheria, Xenarthra, Afrotheria, and Ostentoria (pangolins+carnivores), as well as for the monophyly of the orders Eulipotyphla, Primates, and Rodentia, all of which have recently been questioned. Both data sets recovered an association of Hippopotamidae and Cetacea within Cetartiodactyla, as well as hedgehog and shrew within Eulipotyphla. APOB showed strong support for an association of tarsier and Anthropoidea within Primates. Parsimony, maximum likelihood and Bayesian analyses with both data sets placed Afrotheria at the base of the placental radiation. Statistical tests that employed APOB to examine a priori hypotheses for the root of the placental tree rejected rooting on myomorphs and hedgehog, but did not discriminate between rooting at the base of Afrotheria, at the base of Xenarthra, or between Atlantogenata (Xenarthra+Afrotheria) and Boreoeutheria. An orthologous deletion of 363bp in the aligned APOB sequences proved phylogenetically informative for the grouping of the order Carnivora with the order Pholidota into the superordinal clade Ostentoria. A smaller deletion of 237-246bp was diagnostic of the superordinal clade Afrotheria.

Amino Acid Sequence↗

PubMed2003

Phylogenetics and the conservation of a diverse and ancient flora.

Phylogenetics has a valuable role in the conservation of the flora of Western Australia particularly in the south-west where the complex evolutionary history has resulted in a diverse flora with both relictual and recently evolved components. Phylogenetic analysis contributes to conservation of plants through clarification of taxonomic status, identification of unique evolutionary lineages, determination of relictual and recently derived species, determination of phylogenetic value for conservation priority setting, and identifying phylogenetically independent comparisons between rare and widespread species. The contribution of phylogenetic analysis to these aspects of effective conservation management are discussed with examples from various species in Western Australia.

Australia↗

PubMed2000

Phylogenetic relationships among species of contracaecum Railliet & Henry, 1912 and Phocascaris Høst, 1932 (Nematoda:Ascaridoidea) based on nuclear rDNA sequence data.

Nuclear-encoded large-subunit ribosomal DNA sequences were used to infer a phylogenetic hypothesis for 17 taxa (16 nominal species) of the genera Contracaecum and Phocascaris. Phylogenetic trees based on these data have been used to assess the validity of the taxonomic distinction between these genera, which was based on the presence or absence of certain structural features, rather than on explicit hypotheses of evolutionary history. Phylogenetic hypotheses based on parsimony, likelihood, and neighbor-joining analyses of these sequence data strongly support the hypothesis that species of Phocascaris are nested within the clade of Contracaecum species hosted by phocid seals, and are more closely related to species of the Contracaecum osculatum complex than to other Contracaecum species. Alternative tree topologies representing Phocascaris as not nested within the C. osculatum complex were significantly worse interpretations of these sequence data. Phylogenetic analysis also provides strong support for the monophyly of all taxa (Contracaecum and Phocascaris) from phocid seals, which is consistent with Berland's (1964) proposal that such species form a natural group; however, his proposal to recognize all species in phocid seals as Phocascaris, with all species from birds as Contracaecum would result in a paraphyletic Contracaecum, according to the molecular phylogenetic hypothesis.

Animals↗

PubMed2002

Soft-tissue anatomy of the extant hominoids: a review and phylogenetic analysis.

This paper reports the results of a literature search for information about the soft-tissue anatomy of the extant non-human hominoid genera, Pan, Gorilla, Pongo and Hylobates, together with the results of a phylogenetic analysis of these data plus comparable data for Homo. Information on the four extant non-human hominoid genera was located for 240 out of the 1783 soft-tissue structures listed in the Nomina Anatomica. Numerically these data are biased so that information about some systems (e.g. muscles) and some regions (e.g. the forelimb) are over-represented, whereas other systems and regions (e.g. the veins and the lymphatics of the vascular system, the head region) are either under-represented or not represented at all. Screening to ensure that the data were suitable for use in a phylogenetic analysis reduced the number of eligible soft-tissue structures to 171. These data, together with comparable data for modern humans, were converted into discontinuous character states suitable for phylogenetic analysis and then used to construct a taxon-by-character matrix. This matrix was used in two tests of the hypothesis that soft-tissue characters can be relied upon to reconstruct hominoid phylogenetic relationships. In the first, parsimony analysis was used to identify cladograms requiring the smallest number of character state changes. In the second, the phylogenetic bootstrap was used to determine the confidence intervals of the most parsimonious clades. The parsimony analysis yielded a single most parsimonious cladogram that matched the molecular cladogram. Similarly the bootstrap analysis yielded clades that were compatible with the molecular cladogram; a (Homo, Pan) clade was supported by 95% of the replicates, and a (Gorilla, Pan, Homo) clade by 96%. These are the first hominoid morphological data to provide statistically significant support for the clades favoured by the molecular evidence.

Anatomy, Comparative↗

PubMed2001

Roles of lineage sorting and phylogenetic relationship in the genetic diversity at the self-incompatibility locus of Solanaceae.

Allelic polymorphism at the S locus that determines the gametophytic self-incompatibility (GSI) system in the pistil predates speciation. Understanding the evolution of a GSI system therefore requires knowledge of how lineage sorting and interspecific phylogenetic relationship affect S allele polymorphism. In searching for patterns of lineage sorting among species of various phylogenetic relationships, 22 S-alleles from 34 genets randomly taken at three Tennessee sites from a newly known GSI species Physalis longifolia were sequenced. Analyses of these data along with the previous sequences of three solanaceous species indicate that much of the combined allelic genealogy may be explained by lineage sorting and phylogenetic relationship. Using the mean terminal branch lengths of trans-specific alleles on the allelic genealogy to infer phylogenetic relationship among species, P. longifolia was found to be more closely related to P. cinerascens than to P. crassifolia. Nonetheless, the distribution of terminal branch lengths of P. longifolia was more similar to that of P. crassifolia than to that of P. cinerascens, suggesting phylogenetic relationship may have little effect on species-specific polymorphism. Similar habitat and growth characters, yet contrasting S-polymorphism, between P. longifolia and P. cinerascens also reject previous hypotheses that habitat and growth characters are the major factors responsible for interspecific differences in S-polymorphism. A likely scenario is that species-specific S-polymorphism is based on lineage sorting whose effect is further modified by species age and historical changes in population parameters.

Alleles↗

PubMed2003

Weak phylogenetic effects on ecological niches of Sylvia warblers.

To understand the evolution of ecological niches it is important to know whether niche evolution is constrained by phylogeny. We approached this question for Sylvia warblers by testing if closely related species are more similar in 20 ecologically relevant morphological traits than distantly related species. Phylogenetic relatedness was quantified using a molecular phylogeny based on the mitochondrial cytochrome b gene. By Principal Component Analysis (PCA) two major niche axes were extracted. We tested the individual ecomorphological traits and the positions of the species on the PCA axes for phylogenetic effects using Mantel tests. The results demonstrated small but significant phylogenetic effects only for the length of the middle toe, a trait probably correlated with locomotion. In general, however, phylogenetic effects were very weak. This suggests that ecological niches in passerine birds have the potential to evolve rapidly and are not subject to major phylogenetic constraints.

Adaptation, Physiological↗

PubMed2006

Introduction of a nuclear marker for phylogenetic analysis of Nepenthaceae.

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.

Asia↗

PubMed2004

Phylogenetic discovery bias in Bacillus anthracis using single-nucleotide polymorphisms from whole-genome sequencing.

Phylogenetic reconstruction using molecular data is often subject to homoplasy, leading to inaccurate conclusions about phylogenetic relationships among operational taxonomic units. Compared with other molecular markers, single-nucleotide polymorphisms (SNPs) exhibit extremely low mutation rates, making them rare in recently emerged pathogens, but they are less prone to homoplasy and thus extremely valuable for phylogenetic analyses. Despite their phylogenetic potential, ascertainment bias occurs when SNP characters are discovered through biased taxonomic sampling; by using whole-genome comparisons of five diverse strains of Bacillus anthracis to facilitate SNP discovery, we show that only polymorphisms lying along the evolutionary pathway between reference strains will be observed. We illustrate this in theoretical and simulated data sets in which complex phylogenetic topologies are reduced to linear evolutionary models. Using a set of 990 SNP markers, we also show how divergent branches in our topologies collapse to single points but provide accurate information on internodal distances and points of origin for ancestral clades. These data allowed us to determine the ancestral root of B. anthracis, showing that it lies closer to a newly described "C" branch than to either of two previously described "A" or "B" branches. In addition, subclade rooting of the C branch revealed unequal evolutionary rates that seem to be correlated with ecological parameters and strain attributes. Our use of nonhomoplastic whole-genome SNP characters allows branch points and clade membership to be estimated with great precision, providing greater insight into epidemiological, ecological, and forensic questions.

Bacillus anthracis↗

PubMed2000

Soft-tissue characters in higher primate phylogenetics.

Recent research has cast doubt on the reliability of bones and teeth for reconstructing phylogenetic relationships among higher primate species and genera. Herein, we investigate whether this problem is confined to hard tissues by examining the utility of higher primate soft-tissue characters for reconstructing phylogenetic relationships at low taxonomic levels. We use cladistic methods to analyze 197 soft-tissue characters for the extant hominoids and then compare the resulting phylogenetic hypotheses with the group's consensus molecular phylogeny, which is widely considered to be accurate. We show that the soft-tissue characters yield robust phylogenetic hypotheses that are compatible with the molecular phylogeny. Given the strength of the evidence for molecular phylogeny, these results indicate that, unlike craniodental hard-tissue characters, soft tissues are reliable for reconstructing phylogenetic relationships among higher primate species and genera. Thus, in higher primates at least, some types of morphological data are more useful than others for phylogeny reconstruction.

Animals↗

PubMed2001

Incomplete taxon sampling is not a problem for phylogenetic inference.

A major issue in all data collection for molecular phylogenetics is taxon sampling, which refers to the use of data from only a small representative set of species for inferring higher-level evolutionary history. Insufficient taxon sampling is often cited as a significant source of error in phylogenetic studies, and consequently, acquisition of large data sets is advocated. To test this assertion, we have conducted computer simulation studies by using natural collections of evolutionary parameters--rates of evolution, species sampling, and gene lengths--determined from data available in genomic databases. A comparison of the true tree with trees constructed by using taxa subsamples and trees constructed by using all taxa shows that the amount of phylogenetic error per internal branch is similar; a result that holds true for the neighbor-joining, minimum evolution, maximum parsimony, and maximum likelihood methods. Furthermore, our results show that even though trees inferred by using progressively larger taxa subsamples of a real data set become increasingly similar to trees inferred by using the full sample, all inferred trees are equidistant from the true tree in terms of phylogenetic error per internal branch. Our results suggest that longer sequences, rather than extensive sampling, will better improve the accuracy of phylogenetic inference.

Amino Acids↗

PubMed1996

Accurate reconstruction of a known HIV-1 transmission history by phylogenetic tree analysis.

Phylogenetic analyses are increasingly used in attempts to clarify transmission patterns of human immunodeficiency virus type 1 (HIV-1), but there is a continuing discussion about their validity because convergent evolution and transmission of minor HIV variants may obscure epidemiological patterns. Here we have studied a unique HIV-1 transmission cluster consisting of nine infected individuals, for whom the time and direction of each virus transmission was exactly known. Most of the transmissions occurred between 1981 and 1983, and a total of 13 blood samples were obtained approximately 2-12 years later. The p17 gag and env V3 regions of the HIV-1 genome were directly sequenced from uncultured lymphocytes. A true phylogenetic tree was constructed based on the knowledge about when the transmissions had occurred and when the samples were obtained. This complex, known HIV-1 transmission history was compared with reconstructed molecular trees, which were calculated from the DNA sequences by several commonly used phylogenetic inference methods [Fitch-Margoliash, neighbor-joining, minimum-evolution, maximum-likelihood, maximum-parsimony, unweighted pair group method using arithmetic averages (UPGMA), and a Fitch-Margoliash method assuming a molecular clock (KITSCH)]. A majority of the reconstructed trees were good estimates of the true phylogeny; 12 of 13 taxa were correctly positioned in the most accurate trees. The choice of gene fragment was found to be more important than the choice of phylogenetic method and substitution model. However, methods that are sensitive to unequal rates of change performed more poorly (such as UPGMA and KITSCH, which assume a constant molecular clock). The rapidly evolving V3 fragment gave better reconstructions than p17, but a combined data set of both p17 and V3 performed best. The accuracy of the phylogenetic methods justifies their use in HIV-1 research and argues against convergent evolution and selective transmission of certain virus variants.

Amino Acid Sequence↗