Phylogenetics and evolution of the eastern Asian-eastern North American disjunct aphid tribe,Hormaphidini (Hemiptera: Aphididae)

A conspicuous biogeographic pattern of the Northern Hemisphere is the disjunct occurrence of related taxa on different continents. Perhaps best studied in plants, this pattern includes disjunct distributions of genera in eastern Asia and eastern North America. Such continental disjunctions are thought to be the remnants of a mostly continuously distributed, mixed mesophytic forest dating to the Miocene, which subsequently became fragmented by geological and climatic changes. Some highly host-specific insects, namely aphids, live on descendants of the mixed mesophytic forest taxa and exhibit the same disjunct distributions as that of their host plants. We estimated the phylogeny of Hormaphidini aphids, which host-alternate between witch-hazel (Hamamelis; an eastern Asian-eastern North American disjunct genus) and birch (Betula). Based on partial nuclear elongation factor 1alpha and mitochondrial tRNA leucine/cytochrome oxidase II sequences, trees inferred from maximum-parsimony and maximum-likelihood showed strong support for two monophyletic genera (Hamamelistes and Hormaphis), each containing a clade of Japanese and a clade of North American species. The estimated divergence dates of Asian and North American clades in both genera was 20-30 million years ago, consistent with the idea that aphids may have experienced the same vicariance events as those of their host plants.     

New intermediate host records for the avian schistosomes Dendritobilharzia pulverulenta, Gigantobilharzia huronensis, and Trichobilharzia querquedulae from North America

Here we provide the first North American report of a naturally infected snail, Gyraulus parvus, harboring the larval stages of the cosmopolitan, arterial schistosome, Dendritobilharzia pulverulenta. The relatively small cercariae of this species are shed in the early morning, are sticky, and adhere to the water's surface film. We also provide a report of the snail host, Physa gyrina, of the widespread North American passerine schistosome, Gigantobilharzia huronensis. Finally, we provide unambiguous documentation that Physa gyrina is a natural snail host for Trichobilharzia querquedulae, a schistosome primarily of dabbling ducks.     

Phylogenetic and biogeographical relationships among some holarctic frog lung flukes (Digenea: Haematoloechidae).

A phylogenetic study of 8 North American and European species of frog lung flukes belonging to Haematoloechus was conducted using approximately 850 to 1,000 bases of the intemal transcribed spacer region (ITS 1 + 5.8S + ITS 2) and 1,250 bases of the large subunit (LSU) of the nuclear ribosomal DNA. Adequate phylogenetic resolution could not be obtained from 5.8S or ITS 2 data. Analysis of ITS 1 data produced 2 equally parsimonious trees that differed only in the position of Haematoloechus breviplexus relative to H. medioplexus and H. varioplexus. Single, identical trees were produced by analysis of both LSU sequence data and a data set comprised of all ITS and LSU data. All trees demonstrated 3 distinct evolutionary lineages within the Holarctic Haematoloechus examined. The results confirmed the taxonomic validity of H. abbreviatus and demonstrated that the presence or absence of extracecal uterine loops is not a character meaningful to the recognition of evolutionary lineages or differentiation of genera. Examination of ITS sequence data revealed almost no intraspecific variation within 5 species of Haematoloechus and demonstrated an approximately 150-base indel common to the North American H. longiplexus and the European H. asper. Two of 3 clades revealed by the phylogenetic analyses are comprised of both European and North American species, indicating that lineages of Haematoloechus arose before the breakup of Laurasia and radiated after Eurasia and North America split. Within each of 3 evolutionary lineages, members share similar patterns of arthropod host specificity distinct from patterns found in the other lineages. This suggests that second intermediate host specificity may be a trait that has been conserved through evolutionary time.     

A newly-identified lineage of Schistosoma

Because of their role in causing schistosomiasis, flukes of the genus Schistosoma are the best known of all digeneans. The genus has traditionally been divided into four familiar species groups. Here we report on three poorly known species of Schistosoma, one of which, Schistosoma hippopotami, is known from the hippopotamus, one of which is provisionally identified as Schistosoma edwardiense, another hippo parasite, and a third that has not previously been described. All were collected from freshwater snails obtained from Lake Edward, western Uganda, the type locality for both known hippo schistosomes. The three different kinds of schistosome cercariae differ from one another in size, and all are readily differentiated by their long tail stems from the cercariae of human-infecting species. Furthermore, each was recovered from a different genus of snail host, Biomphalaria sudanica, Bulinus truncatus or Ceratophallus natalensis. Molecular analysis, based on 8350 bases of combined nuclear and mitochondrial DNA, groups these three long tail-stem cercariae into a well supported clade that does not associate with any of the recognised species groups. The placement of this clade, basal to all African species plus several Asian species, suggests that there has been an ancient association between Schistosoma and hippos. This new African Schistosoma clade advocates the need for further modification of the traditional species group-based classification. Two of the four species groups are paraphyletic. It also suggests that Schistosoma has been remarkably plastic with respect to adapting to snail hosts-three distantly related genera of planorbid snails have been exploited by worms within a single clade. Finally, it adds a new layer of complexity to deciphering the origins of Schistosoma, often considered to be African but recently challenged as being Asian. In the late Cenozoic the distribution of hippo species straddled both Africa and Asia and they may have provided a means for the introduction of blood flukes to Africa.     

Phylogeny and taxonomy of the North American clade of the Ceratocystis fimbriata complex

Ceratocystis fimbriata is a widely distributed, plant pathogenic fungus that causes wilts and cankers on many woody hosts. Earlier phylogenetic analyses of DNA sequences revealed three geographic clades within the C. fimbriata complex that are centered respectively in North America, Latin America and Asia. This study looked for cryptic species within the North American clade. The internal transcribed spacer regions (ITS) of the rDNA were sequenced, and phylogenetic analysis indicated that most isolates from the North American clade group into four host-associated lineages, referred to as the aspen, hickory, oak and cherry lineages, which were isolated primarily from wounds or diseased trees of Populus, Carya, Quercus and Prunus, respectively. A single isolate collected from P. serotina in Wisconsin had a unique ITS sequence. Allozyme electromorphs also were highly polymorphic within the North American clade, and the inferred phylogenies from these data were congruent with the ITS-rDNA analyses. In pairing experiments isolates from the aspen, hickory, oak and cherry lineages were interfertile only with other isolates from their respective lineages. Inoculation experiments with isolates of the four host-associated groupings showed strong host specialization by isolates from the aspen and hickory lineages on Populus tremuloides and Carya illinoensis, respectively, but isolates from the oak and cherry lineages did not consistently reveal host specialization. Morphological features distinguish isolates in the North American clade from those of the Latin American clade (including C. fimbriata sensu stricto). Based on the phylogenetic evidence, interfertility, host specialization and morphology, the oak and cherry lineages are recognized as the earlier described C. variospora, the poplar lineage as C. populicola sp. nov., and the hickory lineage as C. caryae sp. nov. A new species associated with the bark beetle Scolytus quadrispinosus on Carya is closely related to C. caryae and is described as C. smalleyi.     

Phylogeny and paraphyly among tetrapod blood flukes (Digenea: Schistosomatidae and Spirorchiidae)

The blood flukes of turtles (Digenea: Spirorchiidae) and the blood flukes of crocodilians, birds and mammals (Digenea: Schistosomatidae) have long been considered as closely related, but distinct evolutionary lineages. Recent morphological and molecular studies have considered these families as sister taxa within the Schistosomatoidea. Representatives of both families have similar furcocercous cercariae and similar two-host life cycles, but have different definitive hosts, distinct reproductive patterns and different morphologies. Sequences including approximately 1800 bases of the small subunit ribosomal DNA and 1200 bases of the large subunit ribosomal DNA were generated from representatives of eight spirorchiid genera. These sequences were aligned with pre-existing sequences of Schistosomatidae and other representatives of the Diplostomida and analysed for phylogenetic signal using maximum parsimony and Bayesian inference. These analyses revealed that the Spirorchiidae is paraphyletic and that the turtle blood flukes are basal to the highly derived schistosomatids. Three genera of spirorchiids from marine turtles form a sister group to the Schistosomatidae and five genera of spirorchiids from freshwater turtles occupy basal positions in the phylogeny of tetrapod blood flukes. Marine turtles are considered to be derived from freshwater turtles and the results of the current study indicate that the spirorchiid parasites of marine turtles are similarly derived from a freshwater ancestor. The close relationship of the marine spirorchiids to schistosomatids and the basal position of the marine transmitted Austrobilharzia and Ornithobilharzia in the schistosomatid clade suggests that schistosomatids arose after a marine turtle blood fluke ancestor successfully colonised birds.     

Constraints on dispersal and the evolution of the avifauna of the Northern Hemisphere

One could predict that the capacity for travelling great distances might predispose long-distance migratory birds to be good colonists and to exhibit wider geographic distributions than their non-migratory or short-distance migratory relatives or non-volant mammals. This prediction is not supported by the data on avian biogeography. The distributions of species, genera and families of North American and Eurasian birds and mammals are indeed related to migratory status, but long-distance migratory birds exhibit a great deal of biogeographic regionalism. In particular, at all taxonomic levels their distributions tend to be confined to either the Eastern or Western Hemisphere, suggesting that there has been little successful east–west dispersal between North America and Eurasia. Compared to non-migratory birds, short-distance migratory birds and non-volant mammals, long-distance migrants appear to be subject to severe constraints on their physiology, behaviour and ecology, w hich have prevented colonization of distant regions.     

根据叶绿体ndhF和核核糖体DNA序列推断梓属(紫葳科)的系统发育

Phylogenetics of Chilopsis and Catalpa (Bignoniaceae) was elucidated based on sequences of chloroplast ndhF and the nrDNA ITS region. In Bignoniaceae, Chilopsis and Catalpa are most closely related as sister genera. Our data supported section Macrocatalpa of the West Indies and section Catalpa of eastern Asian and North American continents. Within section Catalpa, Catalpa ovata of eastern Asia form a clade with North American species, C. speciosa and C. bignonioides, while the other eastern Asian species comprise a clade where C. duclouxii is sister to the clade of C. bungei and C. fargesii. The Caribbean species of Catalpa diverged early from the continental species. More studies are needed to test whether the phylogenetic pattern is common in eastern Asian-North American disjunct genera with species in the West Indies.     

Phylogenetic analysis on genera of Corallobothriinae (Cestoda: Proteocephalidea) from North American ictalurid fishes, using partial sequences of the 28s ribosomal gene

Partial sequences of the 28S rDNA (ribosomal gene) were obtained from a total of 11 populations of 5 species (in 3 genera) of North American corallobothriine proteocephalideans. These included Corallobothrium fimbriatum (3 populations), Corallobothrium parafimbriatum (1 population), Corallotaenia minutia (1 population), Megathylacoides giganteum (2 populations), and Megathylacoides lamothei (4 populations). These sequences were used in a phylogenetic analysis to test the monophyly of Corallobothriinae and to investigate the interrelationships of the North American species. The results indicate that Corallobothriinae, as conventionally understood, is not monophyletic and that only the North American corallobothriines, parasites of ictalurid catfishes, form a monophyletic group. Corallobothrium parafimbriatum is sister taxon to a clade that includes Corallotaenia intermedia and C. minutia and not to its congener C. fimbriatum. Also, M. giganteum from Mexico appears to be more closely related to M. lamothei than to its conspecific in Canada. This and the amount of sequence divergence indicate possible cryptic speciation in its endemic host, the Lerma catfish, Ictalurus dugesi.     

Allobilharzia visceralis gen. nov., sp. nov. (Schistosomatidae-Trematoda) from Cygnus cygnus (L.) (Anatidae)

In Iceland, the examination of whooper swans (Cygnus cygnus L.) viscera resulted in the detection of adult digenean flukes of the family Schistosomatidae. The mature worms occurring in the blood vessels of the large intestine and mesenterium caused vascular lesions, around the eggs deposited in the intestinal mucosa and liver granulomatous reactions developed. The morphology of the isolated schistosomes shows certain similarity with the flukes of the genus Trichobilharzia; in males reduced gynecophoral canal, and on both sexes both suckers and spatulate ends are present. However, the Icelandic flukes possess other morphological features which are distinct from the genus: the point of caecal reunion in males takes place posterior to gynecophoral canal and the genital pore is behind acetabulum and anterior to caecal reunion. In order to evaluate the identity of Icelandic schistosomes, sequencing of ITS region of DNA was performed, and the obtained sequence was deposited in GenBank under the accession no. DQ067561. Following phylogenetic analysis of relationship between the sequence of Icelandic flukes and database sequences of other bird schistosome genera (Trichobilharzia, Gigantobilharzia and Dendritobilharzia) showed different position of Icelandic worms in the phylogenetic tree. In conclusion, our study revealed new genus and species of schistosome flukes--Allobilharzia visceralis gen. et sp. n.     

A molecular phylogeny of malarial parasites recovered from cytochrome b gene sequences

A phylogeny of haemosporidian parasites (phylum Apicomplexa, family Plasmodiidae) was recovered using mitochondrial cytochrome b gene sequences from 52 species in 4 genera (Plasmodium, Hepatocystis, Haemoproteus, and Leucocytozoon), including parasite species infecting mammals, birds, and reptiles from over a wide geographic range. Leucocytozoon species emerged as an appropriate out-group for the other malarial parasites. Both parsimony and maximum-likelihood analyses produced similar phylogenetic trees. Life-history traits and parasite morphology, traditionally used as taxonomic characters, are largely phylogenetically uninformative. The Plasmodium and Hepatocystis species of mammalian hosts form 1 well-supported clade, and the Plasmodium and Haemoproteus species of birds and lizards form a second. Within this second clade, the relationships between taxa are more complex. Although jackknife support is weak, the Plasmodium of birds may form 1 clade and the Haemoproteus of birds another clade, but the parasites of lizards fall into several clusters, suggesting a more ancient and complex evolutionary history. The parasites currently placed within the genus Haemoproteus may not be monophyletic. Plasmodium falciparum of humans was not derived from an avian malarial ancestor and, except for its close sister species, P. reichenowi, is only distantly related to haemospordian parasites of all other mammals. Plasmodium is paraphyletic with respect to 2 other genera of malarial parasites, Haemoproteus and Hepatocystis. Explicit hypothesis testing supported these conclusions.     

Influence of Host and Geographic Locale on the Distribution of Colletotrichum cereale Lineages

Colletotrichum cereale is an ascomycete inhabitant of cool-season Pooideae grasses. The fungus has increased in frequency over the past decade as a destructive pathogen of Poa annua and Agrostis stolonifera turfgrass. Colletotrichum cereale exists as two lineages, designated clades A and B, but little is known about the distribution of these clades in natural environments, or what role these subdivisions may play in the trajectory of disease outbreaks. In this study, our objective was to determine the frequency of C. cereale clades A and B. To rapidly discriminate between the two C. cereale clades, a real-time PCR assay was developed based on the Apn2 gene. A collection of 700 C. cereale pathogens and endophytes from twenty Pooideae grass genera were genotyped. 87% of the collection was identifed as part of clade A, 11.7% as part of clade B, and 1.3% was a mixture. Colletotrichum cereale from turfgrass hosts in North America were most commonly members of clade A (78%). The overabundance of clade A in turfgrass isolates was directly attributable to the dominance of this lineage from southern sampling sites, irrespective of host. In contrast, 111 C. cereale turfgrass isolates collected from northern sampling sites were evenly distributed between clades A and B. Only 28% of C. cereale from A. stolonifera at northern sampling sites were part of clade A. These data show that environmental factors such as geographic location and host identity likely played a role in the distribution of the major C. cereale clades in North American turfgrass.     

Sequence determination of a new parrot bornavirus‐5 strain in Japan: implications of clade‐specific sequence diversity in the regions interacting with host factors

In this study, the genome sequence of a new parrot bornavirus‐5 (PaBV‐5) detected in Eclectus roratus was determined. Phylogenetic analysis showed that the genus Bornavirus is divided into three major clades and that PaBV‐5 belongs to clade 2, which contains avian viruses that exhibit infectivity to mammalian cells. Sequence comparisons of the regions known to interact with host factors indicated that the clade 2 avian viruses possess sequences intermediate between the clade 1 mammalian viruses and the clade 3 avian viruses, suggesting that the identified regions might contribute to the differences in virological properties between the three clades.     

Molecular systematics and radiation of western North American nymphophiline gastropods

Three mitochondrial DNA (mtDNA) markers were used to infer the phylogenetic relationships of the morphologically diverse, species rich, and poorly understood western North American aquatic gastropod genus Pyrgulopsis (Hydrobiidae: Nymphophilinae). Sequences were obtained from 62 of 124 currently recognized species of Pyrgulopsis and representatives of four related genera of North American nymphophilines. Separate and combined analyses of the mtDNA datasets recovered a well supported clade composed of Pyrgulopsis and two other North American nymphophiline genera (Floridobia, Nymphophilus) consistent with the results of a prior study based on a single gene and with anatomical evidence suggesting that these taxa form a monophyletic group. Phylogenetic relationships among lineages of Pyrgulopsis were little resolved in our analyses and provided no obvious basis for splitting this large genus into multiple genera. The little differentiated Mexican genus Nymphophilus was consistently placed within Pyrgulopsis in our trees and is formally synonymized with it herein. Pyrgulopsis was also depicted as paraphyletic with respect to Floridobia in some of our trees while in others the latter was sister to a Nymphophilus + Pyrgulopsis clade. Based on these equivocal results and the morphological and geographical divergence of eastern North American Floridobia relative to Pyrgulopsis, we recommend that the former be maintained as a separate genus. The short, weakly supported branches within Pyrgulopsis and the noncongruence between our molecular phylogenetic hypotheses and geographical groupings of species are attributed to an early rapid diversification of the genus, perhaps triggered by the complex changes in western topography which occurred during the late Tertiary. Our results also indicate that penial morphologies used to define species groups of Pyrgulopsis have been subject to striking convergence throughout the West, suggesting another compelling facet of the radiation of these snails.     

Molecular systematics of a speciose, cosmopolitan songbird genus: defining the limits of, and relationships among, the Turdus thrushes

The avian genus Turdus is one of the most speciose and widespread of passerine genera. We investigated phylogenetic relationships within this genus using mitochondrial DNA sequence data from the ND3, ND2 and cytochrome b genes. Our sampling of Turdus included 60 of the 65 extant species currently recognized, as well as all four species from three genera previously shown to fall inside Turdus (Platycichla, Nesocichla, and Cichlherminia). Phylogenetic trees based on maximum likelihood and maximum parsimony algorithms were congruent. Most of the Turdus taxa sampled fall into one of four clades: an African clade, a Central American-Caribbean clade, a largely South American clade, and a Eurasian clade. Still other taxa are placed either at the base of Turdus, or as links between clades. In no instance is any continent reciprocally monophyletic for the species distributed on it. A general lack of nodal support near the base of the phylogeny seems related to a rapid intercontinental establishment of the major clades within Turdus very early in the history of the genus. The monotypic genus Psophocichla is distantly related to, but clearly the sister of, Turdus rather than a constituent member of it.     

Avian louse phylogeny (Phthiraptera: Ischnocera): a cladistic study based on morphology

The louse suborder Ischnocera (Phthiraptera) contains 3060 currently described species from over 150 genera. These lice are permanent obligatory ectoparasites of a diverse selection of birds and mammals with a worldwide distribution. Historically, they have played a major role in the development of our ideas on coevolution, and species hosted by mammals have been used extensively as model organisms for the study of cospeciation. In contrast, avian taxa comprising 90% of ischnoceran species have been neglected due to a lack of data on their wider systematics. A comparative study based on the adult and nymphal instar morphology of avian lice yielded 138 characters from 56 species (51 genera), all of which are illustrated or discussed here for the first time. A further five outgroup taxa were examined from the mammalian ischnoceran family Trichodectidae. Phylogenetic analyses of these data produced three most parsimonious cladograms, the strict consensus of which is highly resolved and broadly consistent with previous classifications. Morphological character variation is extensive, and nymphal character traits are useful in identifying instances of convergent evolution in adult morphology. The role of ontogeny in the development of the major character complexes of the head and abdomen is discussed, and its implications for further work on the phylogeny of avian Ischnocera is considered. Comparison with host taxonomy reveals a series of complex host-parasite associations that do not support a hypothesis of strict one to one cospeciation. However, extrapolation of these associations is compromised by the low sample size. The role of niche specialization to explain the presence of multiple unrelated lineages on the same host taxon is considered.     

A molecular phylogeny of the nightjars (Aves: Caprimulgidae) suggests extensive conservation of primitive morphological traits across multiple lineages

We report a molecular re-assessment of the classification of the nightjars which draws conclusions that are strongly at odds with the traditional, morphology-based classifications. We used maximum likelihood and Bayesian methods to compare the cytochrome b gene for 14 species from seven of the 15 genera of the Caprimulgidae and partial cytochrome b sequence data was available for a further seven species including three further genera. We found that within the Caprimulgidae there were four geographically isolated clades with bootstrap support greater than 70%. One of these clades contained just Chordeiles species, the remaining three clades each contained a mixture of genera including Caprimulgus sp. A clade of exclusively South American nightjars included the genera Caprimulgus, Uropsalis, Eleopthreptus and Hydropsalis. A clade of African and Eurasian birds included Caprimulgus and Macrodipteryx. Phalaenoptilus nuttallii and Caprimulgus vociferous formed a clade of North American birds. Two ecological factors appear to make morphological classification potentially misleading: first, the apparent retention of primitive anti-predator and foraging-related traits across genetically divergent groups; second, rapid divergence in other traits, especially those related to mating, which generate high levels of morphological divergence between species that are genetically very similar. The cytochrome b data suggests that the genus Caprimulgus is not monophyletic and is restricted to Africa and Eurasia and that Caprimulgus species from outside this area have been misclassified as a consequence of retention of primitive adaptations for crepuscular/nocturnal living. Some other genera also appear to have little support from the cytochrome b data.     

Molecular systematics of North American phoxinin genera (Actinopterygii: Cyprinidae) inferred from mitochondrial 12S and 16S ribosomal RNA sequences

The cyprinid fish fauna of North America is relatively large, with approximately 300 species, and all but one of these are considered phoxinins. The phylogenetic relationships of the North American phoxinins continue to pose difficulties for systematists. Results of morphological analyses are not consistent owing to differences interpreting and coding characters. Herein, we present phylogenetic analyses of mitochondrial 12S and 16S ribosomal RNA sequence data for representatives of nearly all genera of North American phoxinins. The data were analysed using parsimony, weighted parsimony, maximum likelihood and bayesian analyses. Results from weighted parsimony, likelihood and the bayesian analysis are largely consistent as they all account for differing substitution rates between transitions and transversions. Several major clades within the fauna can be recognized and are strongly supported by all analyses. These include the western clade, creek chub–plagopterin clade and the open posterior myodome clade. The shiner clade is nested in the open posterior myodome clade and is the most species-rich clade of North American phoxinins. Relationships within this clade were not well resolved by our analyses. This may reflect the inability of the mitochondrial RNA genes to resolve recent speciation events or taxon sampling within the shiner clade.  © 2003 The Linnean Society of London, Zoological Journal of the Linnean Society , 2003, 139 , 63–80.