Geographic and host range of the nematode Soboliphyme baturini across Beringia

The nematode Soboliphyme baturini Petrov, 1930, was found to represent a single species with a relatively broad geographic range across Beringia and northwestern North America on the basis of the assessment of molecular sequence data for adult and juvenile parasites. Refuted are hypotheses suggesting that several cryptic species could be partitioned either among an array of mustelid definitive hosts or across the vast region that links North America and Eurasia. Host specificity for this species is examined on the basis of a comprehensive list for definitive hosts, derived from new field surveys and existing literature for S. baturini. Only 5 mustelids (Gulo gulo, Martes americana, M. caurina, M. zibellina, and Neovison vison) appear to have significant roles in the life history, persistence, and transmission of this nematode. Soboliphyme baturini readily switches among M. americana, M. caurina, Mustela erminea, or N. vison at any particular locality throughout its geographic range in North America, although Martes spp. could represent the source for nematodes in a broader array of mustelids. Molecular analyses (243 base pairs of mitochondrial gene nicotinamide dehydrogenase [ND4]) suggest that hypotheses for host specificity across an array of mustelid definitive hosts are not supported. The life cycle of S. baturini is explored through a review of diet literature for 2 marten species, M. americana and M. caurina, and other mustelids across the Holarctic. Shrews (Soricomorpha: Soricidae) comprise >8% of prey for these species of Martes, suggesting their putative role as paratenic hosts. Juvenile nematodes found in the diaphragms of soricids are genetically identical to adult S. baturini found in the stomachs of mustelids at the same locations in both Asia and North America, corroborating a role in transmission for species of Sorex.     

Soboliphyme baturini infection does not affect the nutritional condition of American marten (Martes americana) in Alaska

Soboliphyme baturini, a stomach-dwelling nematode of American martens (Martes Americana), reaches high levels of infection; however, its effects on the nutritional condition of the host are unknown. To understand the effects of this parasite on American martens, we collected S. baturini and measured abdominal fat deposits from 155 marten carcasses on Prince of Wales Island, southeastern Alaska, in the winter 2006-2007. We analyzed how the dried mass of abdominal fat varied as a function of S. baturini intensity. Parasite intensity and nutritional condition were not correlated; these results suggest that American martens were able to withstand even very high levels of S. baturini infection (up to 178 parasites per host).     

Polymorphism hides cryptic species in Oerstedia dorsalis (Nemertea, Hoplonemertea)

The marine hoplonemertean Oerstedia dorsalis is considered to be a highly polymorphic species with extensive geographic distribution. We show, based on mitochondrial cytochrome c oxidase subunit I, 16S and nuclear internal transcribed spacer sequences, that there are genetic subsets withing this species. Seventy-one specimens of various colours from different geographic localities (in Europe) were sequenced and analysed using statistical parsimony and Bayesian analysis. Both analyses supported nine major clades. We conclude that O. dorsalis hides different species with geographic resolution. These species, however, appear to be polymorphic as well, and we find no diagnostic features in pigmentation or external characters to separate species within this complex.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 556–567.     

Historical and ecological correlates of body shape in the brook stickleback, Culaea inconstans

Using geometric morphometric methods, we evaluated the correlation between phenotypic variation and available historical and habitat information for two genetically differentiated, allopatric lineages of a widespread North American species, the brook stickleback ( Culaea inconstans ). The results obtained revealed strong patterns of structured phenotypic differentiation across the species range with extreme phenotypes occurring at the northwest and southeast range boundaries. Shape variation was broadly congruent with the distribution of two mitochondrial DNA lineages; a deep-bodied eastern form (Atlantic refugium) and a slim-bodied western form (Mississippian refugium); however, the two forms were not lineage-specific and phenotypic cladistic diversification is likely to be an artefact of underlying clinal variation associated with longitudinal and latitudinal gradients. In addition, we found little evidence of diagnosable lake and river forms across North America. Taken together, large-scale patterns of phenotypic diversity observed in C. inconstans suggest that relatively recent factors, such as continually varying natural selection across the range and/or potential local gene flow, may substantially mitigate the effects of historical separation or a generalized adaptive response to alternative habitats.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 769–783.     

Discordance in body size, colour pattern, and advertisement call across genetically distinct populations in a Neotropical anuran (Dendropsophus ebraccatus)

Patterns of intraspecific geographic variation in morphology and behaviour, when examined in a phylogenetic context, can provide insight into the microevolutionary processes driving population divergence and ultimately speciation. In the present study, we quantified behavioural and phenotypic variation among populations from genetically divergent regions in the Central American treefrog, Dendropsophus ebraccatus . Our fine-scale population comparisons demonstrated regional divergence in body size, colour pattern frequencies, and male advertisement call. None of the characters covaried with phylogenetic history or geographic proximity among sampled populations, indicating the importance of highly localized selection pressures and genetic drift in shaping character divergence among isolated regions. The study underscores how multiple phenotypic characters can evolve independently across relatively small spatial scales.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 298–313.     

Historical biogeography of Hexabathynella , a cosmopolitan genus of groundwater Syncarida (Crustacea, Bathynellacea, Parabathynellidae)

Hexabathynella is the only cosmopolitan genus of the order Bathynellacea (Crustacea). The known species number 18, found in Europe (9), Africa (1), South America (2), North America (3) and Australia and New Zealand (3). Phylogenetic analysis suggests that the least derived species are those from South America and the most derived those from the Iberian Peninsula, North America and Australia. The five species with the most plesiomorphic characters occur in salt or brackish water, which supports a marine origin for the genus. Phylogenetic and biogeographical analyses suggest that the distribution of the genus can be explained by dispersion and a double vicariant biogeographical model based on plate tectonics and the evolution of the Tethys during the Mesozoic and Cenozoic.  © 2003 The Linnean Society of London . Biological Journal of the Linnean Society , 2003, 78 , 457–466.     

Prevalence of Soboliphyme baturini in marten (Martes americana) populations from three regions of Alaska, 1990-1998

Marten (Martes americana) carcasses were collected from trappers in three regions of Alaska. Stomachs were examined for the nematode parasite Soboliphyme baturini. Both prevalence and intensity of infection exhibited an increase from north to south. Prevalence was higher in adults (compared with juveniles) from the two mainland study areas. Prevalences in these two age classes were similar for the southeastern region. There were no sex-specific differences in prevalence. No pathologic changes were observed in the gastrointestinal tract. Impact of the parasite on either individual animals or populations was not detected.     

Palaeoclimatic variation, adaptation and biogeography of inversion polymorphisms in natural populations of Drosophila robusta

Studies of natural and sexual selection in wild populations of Drosophila have historically provided strong inference for the maintenance of inversion polymorphism. Analysis of geographical variation in the Drosophila robusta chromosomal data collected over more than 50 years from 133 natural populations across eastern North America has confirmed several north–south and east–west clines in the frequencies of some gene arrangements and linked arrangement combinations. Patterns of geographical variation, including several north–south clines, revealed by regression and spatial autocorrelation analyses are concordant with palaeoclimatic shifts, Pleistocene glaciations and historical changes in the composition of North American forest communities. Because D. robusta is a sap-breeder, using the microbe-infested sap exudates of a number of deciduous tree species in which they carry out their life cycle, shifts in climate and palaeovegetation types since the formation of the eastern deciduous forests in the Miocene are hypothesized to be major factors influencing patterns of inversion polymorphisms across the range of this drosophilid species. In areas where sharp deviations in frequencies have been observed, particularly in the mid-western and western portions of the range, these divisions parallel historical geographical disjunctions in the species range that have yet to promote divergence and species formation despite the long history of D. robusta in North America.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 81 , 395–411.     

Sarcinomyces sideticae, a new black yeast from historical marble monuments in Side (Antalya, Turkey)

A new species of Sarcinomyces , a melanized fungus with meristematic development, is described. On the basis of small subunit and internal transcribed sequence regions of ribosomal DNA sequencing, the new species was accommodated in the anamorph genus Sarcinomyces (Herpotrichiellaceae, Chaetothyriales) close to S. petricola .  © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 154 , 373–380.     

Different phylogeographic patterns in two Japanese Silpha species (Coleoptera: Silphidae) affected by climatic gradients and topography

To reveal differences in phylogeographic patterns of flightless insect species occurring in different regions of Japan, we studied the phylogeography and demographic history of Silpha beetles occurring in cool-temperate habitats of two major islands, Honshu and Hokkaido, using sequences of the mitochondrial cytochrome oxidase subunit I (COI) gene. Honshu has a more mountainous topography, and cool-temperate habitats occur discontinuously, whereas Hokkaido, located to the north of Honshu, has more continuous cool-temperate habitats. A species endemic to Honshu, S. longicornis occurs on Honshu, whereas S. perforata occurs on Hokkaido and the East Asian continent. Our results indicate that the ancestors of S. longicornis colonized Honshu via a south-west route c . 0.7 Mya and the species has highly divergent populations in isolated mountainous areas of Honshu, whereas S. perforata colonized Hokkaido via a northern route less than 90 000 years ago and has less divergent geographic populations. During the last glacial period, S. perforata was probably restricted to refugia in southern Hokkaido and later expanded into northern Hokkaido, whereas S. longicornis populations existed in many isolated refugia, probably because of the complex topography of Honshu. Thus, our study demonstrates that, even between closely related species, interactions among biology, latitudinal climatic gradients and topography can produce different phylogeographic patterns.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 452–467.     

Species diversity and endemism in the Daphnia of Argentina: a genetic investigation

Although the temperate regions of South America are known to have a diverse daphniid fauna, there has been no genetic evaluation of the existing taxonomic system or of the affinities between the North and South American faunas. The present study analyses mitochondrial DNA sequences and allozyme variation to investigate species diversity in 176 Daphnia populations from Argentina. This work established the presence of at least 15 species in Argentina, six of which are either undescribed or are currently misidentified and two of which represent range extensions of North American taxa. Eleven of the Argentine species appear endemic to South America, while the remaining four also occur in North America. In the latter cases, the close genetic similarity between populations from North and South America indicates the recent exchange of propagules between the continents. While biological interactions and habitat availability have undoubtedly contributed to the observed species distributions, chance dispersal has apparently played a dominant role in structuring large-scale biogeographical patterns in this genus and probably in other passively-dispersed organisms.  © 2004 The Linnean Society of London, Zoological Journal of the Linnean Society , 2004, 140 , 171−205.     

Investigating South American biogeographic history using patterns of skull shape variation on Cerdocyon thous (Mammalia: Canidae)

Patterns of geographic variation of the canid Cerdocyon thous have historically been obscured by its remarkable intraspecific morphological variability. The observed distribution is highly associated with phytophysiognomy, a feature considered highly dynamic along geological time. In the present study, we tested whether vegetation distribution during the Holocene Glacial Maximum of South America (HGM) explains the patterns of morphological variation within Cerdocyon thous . The species was divided in groups according to paleohabitats that could support their presence during the HGM, and then tested for differences in skull morphometrics. The results obtained demonstrate that the climatic changes during the HGM influenced the population structure of this species, resulting in the establishment of geographical groups with different degrees of morphological cohesion. Higher morphological cohesion found in the Northern group might be explained by the marked discontinuity between its geographical range and the rest of the species'distribution. The Eastern and Southern morphological divergence is less striking and, although this could be related to past vegetation distribution, the disappearance of those barriers leads to a population structure that could be slowly breaking down.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 77–84.     

Molecular characterization of an ancient Hepatozoon species parasitizing the 'living fossil' marsupial 'Monito del Monte' Dromiciops gliroides from Chile

The Microbiotheriid Dromiciops gliroides , also known as 'Monito del Monte', is considered to be a threatened species and the only living representative of this group of South American marsupials. During the last few years, several blood samples from specimens of 'Monito del Monte' captured at Chiloé island in Chile have been investigated for blood parasites. Inspection of blood smears detected a Hepatozoon species infecting red blood cells. The sequences of DNA fragments corresponding to small subunit ribosomal RNA gene revealed two parasitic lineages belonging to Hepatozoon genus. These parasite lineages showed a basal position with respect to Hepatozoon species infecting rodents, reptiles, and amphibians but are phylogenetically distinct from Hepatozoon species infecting the order Carnivora. In addition, the Hepatozoon lineages infecting D. gliroides are also different from those infecting other micro-mammals living in sympatry, as well as from some that have been described to infect an Australian species of bandicoot. The potential vector of this parasite appears to be the host-specific tick Ixodes neuquenensis because the sequencing of a long amplicon determined the presence of one of the two lineages found in the marsupial.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 568–576.     

Spatial expansion and population structure of the neotropical malaria vector, Anopheles darlingi (Diptera: Culicidae)

Extensive population structuring is known to occur in Anopheles darlingi , the primary malaria vector of the Neotropics. We analysed the phylogeographic structure of the species using the mitochondrial cytochrome oxidase I marker. Diversity is divided into six main population groups in South America: Colombia, central Amazonia, southern Brazil, south-eastern Brazil, and two groups in north-east Brazil. The ancestral distribution of the taxon is hypothesized to be central Amazonia, and there is evidence of expansion from this region during the late Pleistocene. The expansion was not a homogeneous front, however, with at least four subgroups being formed due to geographic barriers. As the species spread, populations became isolated from each other by the Amazon River and the coastal mountain ranges of south-eastern Brazil and the Andes. Analyses incorporating distances around these barriers suggest that the entire South American range of An. darlingi is at mutation–dispersal–drift equilibrium. Because the species is distributed throughout such a broad area, the limited dispersal across some landscape types promotes differentiation between otherwise proximate populations. Moreover, samples from the An. darlingi holotype location in Rio de Janeiro State are substantially derived from all other populations, implying that there may be additional genetic differences of epidemiological relevance. The results obtained contribute to our understanding of gene flow in this species and allow the formulation of human mosquito health protocols in light of the potential population differences in vector capacity or tolerance to control strategies.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 854–866.     

Helminth parasitism in martens (Martes americana) and ermines (Mustela erminea) from Washington, with comments on the distribution of Trichinella spiralis

Helminths are reported for the first time from ermines (Mustela erminea) and martens (Martes americana) in Washington (USA). Among 22 adult ermines, 41% were infected by one or more of five species (Taenia mustelae, Alaria mustelae, Molineus patens, M. mustelae and Trichinella spiralis). Among 78 adult martens from three geographic localities, the prevalence was 83%. Nine species were identified (Mesocestoides sp., T. mustelae and T. martis americana, Euryhelmis squamula, M. patens, Baylisascaris devosi, Physaloptera sp., Soboliphyme baturini and T. spiralis). Trichinella spiralis occurred with a maximum prevalence of 50% in martens, but only occurred in 9% of ermines. Compression and digestion techniques provided a similar estimate of prevalence of T. spiralis, yet neither was entirely accurate in identifying all infected hosts. The species richness of the helminth community of martens in Washington was greater than that reported from other regions of North America.     

A new leptarctine (Carnivora: Mustelidae) from the early Miocene of the northern Tibetan Plateau: implications for the phylogeny and zoogeography of basal mustelids

A recently discovered basal mustelid carnivoran, Kinometaxia guangpui gen. et sp. nov. , is described from the lower Miocene Tiejianggou Formation in the Danghe (Tabenbuluk) area of the northern Tibetan Plateau, north-western Gansu Province, China. The new Chinese form has a double temporal crest and roughened surface on the temporal area, a small orbit, a deep zygomatic arch, an anterolaterally expanded ectotympanic that fuses with the postglenoid process, and a lateral opening of the postglenoid foramen. These cranial morphologies suggest membership in the leptarctines, a group of markedly hypocarnivorous taxa mostly confined to the Miocene of North America. The rather hypercarnivorous dentition of the new Chinese form, however, is in sharp contrast to that of the traditionally defined leptarctines that have complex and quadrate M1s and P4s. Phylogenetic analysis suggests a sister relationship of the new Chinese mustelid and Schultzogale , and together they form a basal sister clade to the advanced leptarctines such as Craterogale , Leptarctus , and Hypsoparia . The Chinese form further expands the concept of the leptarctine clade and adds additional complexity to the early evolution of the Mustelidae. It bridges a morphological gap between European and North American taxa, and supplies an important piece to the puzzle of the zoogeography of basal mustelids. Furthermore, the new leptarctine helps to constrain the age of the Danghe strata, which has important implications for the timing of tectonic activity in the northern Tibetan Plateau.  © 2004 The Linnean Society of London, Zoological Journal of the Linnean Society , 2004, 142 , 405−421.     

Phenotypic and genetic differentiation of two major phylogeographical lineages of arctic grayling Thymallus arcticus in the Lena River, and surrounding Arctic drainages

Two phylogeographical lineages of arctic grayling, Thymallus arcticus , in Siberia are extensively characterized based on both molecular genetic (mtDNA control region sequences) and phenotypic (12 meristic characters) data. One lineage, occurring in the delta region of the Lena River as well as all other Arctic draining rivers sampled, corresponds to the subspecific taxon Thymallus arcticus pallasii , whose type locality is the Kolyma River. This taxon is proposed to be a postglacial colonizer of the Lena delta. The second lineage occurs throughout the rest of the Lena basin and is proposed to have survived in a glacial refugium in the middle reaches of the Lena. These lineages form reciprocally monophyletic groups based on mtDNA sequences (net divergence 3.2%), a relationship that is concordant with phenotypic data, and thus reflects distinct taxa. The upper Lena taxon is given the preliminary name of Thymallus arcticus lenensis . Phylogenetic analysis, together with previously published data from North America, reveals that mtDNA sequences from North American populations group within the diverse clade corresponding to T. a. pallasii in Siberia. Despite the relatively close genetic relationship of most North American haplotypes with those in northern Siberia, inferences of fragmentation between the continents are supported, but bidirectional movements between the two continents are seen as likely. Despite inclusion in the clade representing T. a. pallasii in Siberia, the source of the relatively divergent Nahanni refuge haplotypes in North America is not resolved. Otherwise, inferences of postglacial expansion across several thousand kilometres are well supported within North America, but only smaller-scale colonization events among drainages are supported in Siberia.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 88 , 511–525.     

Ecological niche conservatism in North American freshwater fishes

There are many hypotheses of relationships, and also of speciation processes, in North American freshwater fishes, although, to date, there have been no direct tests of whether there is evidence of ecological niche conservatism. In the present study, ecological niche modeling is used to look for evidence of ecological niche conservatism in six clades of freshwater fishes: the starheaded topminnows, sand darters, black basses, Notropis rubellus species group, Notropis longirostris species group, and the Hybopsis amblops species group. This is achieved by evaluating the reciprocal predictivity of distributional predictions based on ecological niche models developed for each individual taxon in a clade under the assumption that high reciprical predictivity between sister species can be taken as evidence of niche conservatism. Omission percentages, total and average commission, and the area under the curve in a receiver operating characteristic analysis, where calculated, are used to evaluate predictive ability. Occurrence data for each species were subset into a training and independent validation data set where possible. Across all clades and species, models predicted the validation data for a given species well. Ecological niche conservatism was found generally across the starheaded topminnows, the sand darters, and the N. longirostris species group. There was some inter-predictivity within the N. rubellus group, but almost no inter-predictivity within the black basses, indicating a lack of conservatism. These results demonstrate that ecological niches generally act as stable constraints on freshwater fish distributions in North America.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 282–295.     

Coevolution of daily activity timing in a host–parasite system

Coevolutionary theories applied in the study of host–parasite systems indicate that lineages exhibit progressive trends in response to reciprocal selective pressures. Avian brood parasites have generated intense interest as models for coevolutionary processes. Similar to avian cuckoos, Polistes wasp social parasites usurp a nest and exploit the parental care of a congeneric species to rear their own brood. In the present study, we show a coevolutionary arms race in the daily activity pattern in a Polistes host–parasite pair. We measured the daily activity rate, in constant laboratory conditions, of both host and parasite females during the period in which nest usurpations occur. The parasites showed a hyperkinesis in the middle of the day. As the field observations suggested, this mid-day activity is used to perform host nest usurpation attempts. Timing the usurpations allows the parasite to maximize its usurpation attempts during daytime when the host defence is lower. A field comparison of host presence on the nest in two populations with different parasitism rates showed that populations under strong parasitic pressure exhibit timing counteradaptations to optimize nest defence. This study provides the first example of a mutual coadaptation in timing activity in a parasite–host system.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 399–405.