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C Moritz

Publications and source records attributed to C Moritz.

At least 37 records · Page 2Linked to original sources
PubMed1999

Reticulate evolution and the origins of ribosomal internal transcribed spacer diversity in apomictic Meloidogyne.

Among root knot nematodes of the genus Meloidogyne, the polyploid obligate mitotic parthenogens M. arenaria, M. javanica, and M. incognita are widespread and common agricultural pests. Although these named forms are distinguishable by closely related mitochondrial DNA (mtDNA) haplotypes, detailed sequence analyses of internal transcribed spacers (ITSs) of nuclear ribosomal genes reveal extremely high diversity, even within individual nematodes. This ITS diversity is broadly structured into two very different groups that are 12%-18% divergent: one with low diversity (< 1.0%) and one with high diversity (6%-7%). In both of these groups, identical sequences can be found within individual nematodes of different mtDNA haplotypes (i.e., among species). Analysis of genetic variance indicates that more than 90% of ITS diversity can be found within an individual nematode, with small but statistically significant (5%-10%; P < 0.05) variance distributed among mtDNA lineages. The evolutionarily distinct parthenogen M. hapla shows a similar pattern of ITS diversity, with two divergent groups of ITSs within each individual. In contrast, two diploid amphimictic species have only one lineage of ITSs with low diversity (< 0.2%). The presence of divergent lineages of rDNA in the apomictic taxa is unlikely to be due to differences among pseudogenes. Instead, we suggest that the diversity of ITSs in M. arenaria, M. javanica, and M. incognita is due to hybrid origins from closely related females (as inferred from mtDNA) and combinations of more diverse paternal lineages.

Animals↗
PubMed1998

Phylogeography of Bufo marinus from its natural and introduced ranges.

The marine toad, Bufo marinus, has a broad natural distribution extending from the south-west of the USA to southern Peru and the central Amazon. It was introduced to several localities in the Caribbean and Pacific Oceans to control sugar cane pests. We sequenced 468 bp of mitochondrial DNA (mtDNA) containing the ND3 gene, and flanking tRNA genes from toads spanning the broad natural and introduced ranges. Consistent with the known history of introductions and expected effects of serial bottlenecks, mtDNA within introduced populations in Hawaii and Australia was uniform and most closely related to samples from eastern Venezuela and French Guiana. However, mtDNA nucleotide diversity in the geographic region spanning the source areas is also relative low (0.18-0.46%) and the absence of variation in the introduced populations precludes quantitative assessment of the reduction in genetic diversity. Unexpectedly, there was a large phylogeographic break (5.4% sequence divergence) within the natural range separating populations east and west of the Venezuelan Andes. We hypothesize that the two major lineages of B. marinus were isolated by the uplift of the eastern Andean cordillera which was completed approximately 2.7 Ma. Another species of the marinus group, B. paracnemis, had mtDNA paraphyletic, with marinus, being nested within the eastern lineage. Thus, at least one speciation event within the marinus group postdates the split within marinus. These findings suggest that the taxonomy of B. marinus should be re-evaluated and that the search for pathogens to control Australian populations should be conducted in populations from both lineages in the natural range.

Animals↗
PubMed1998

Phylogenetic relationships between oviparous and viviparous populations of an Australian lizard (Lerista bougainvillii, scincidae).

Viviparity has evolved from oviparity in many vertebrate lineages, and species that contain both oviparous and viviparous populations offer the best opportunity for a detailed examination of the processes involved in this major life-history transition. However, although several such species have been reported, none have been the subject of detailed phylogenetic analyses. We examine such a case within the Australian scincid lizard bougainvillii. Data were obtained by sequencing a 314-bp segment of mitochondrial cytochrome b from 32 individuals from 17 populations of L. bougainvillii and two morphologically similar congeneric species (L. dorsalis L. microtus). Sequences were aligned and analyzed using parsimony and distance methods. The resultant matriarchal phylogeny resolved the populations of L. bougainvillii into three major groups: a population from NSW; a group predominantly from Eyre Peninsula; and a less well-defined group from the central part of the species range. The NSW and Eyre Peninsula groups are oviparous and are quite divergent from other L. bougainvillii populations and from each other. The central group contains both viviparous and oviparous populations, and seem to represent a more recent radiation within the species. Our results indicate that viviparity has evolved at least twice within the genus Lerista, because the viviparous L. microtus is not closely related to viviparous populations of L. bougainvillii. The lack of phylogenetic separation of mtDNAs from viviparous and oviparous populations within L. bougainvillii relative to strong geographic structure within the latter indicates that populations with different reproductive modes are indeed conspecific. Lerista bougainvillii is thus the first vertebrate species for which intraspecific bimodality in reproductive mode can be claimed with any certainty.

Animals↗
PubMed1998

Mitochondrial DNA diversity and historical biogeography of a wet forest-restricted frog (Litoria pearsoniana) from mid-east Australia.

MtDNA sequencing was used to investigate the genetic population structure of Litoria pearsoniana, a wet forest-restricted hylid frog, endemic to southeast Queensland and northeast New South Wales, Australia. L. pearsoniana is regarded as endangered under Queensland legislation. Significant genetic divergence among populations of frogs from different rainforest isolates was identified, but the lack of reciprocal monophyly among adjacent isolates suggests this is the result of a relatively recent disruption to gene flow. A paired catchment study within a single rainforest isolate, the Conondale Range, revealed no substantial genetic structuring, indicating the occurrence of terrestrial dispersal among nearby streams either in the recent past or currently. Two major reciprocally monophyletic clades of mtDNA alleles were identified. These corresponded to two geographical regions separated by the Brisbane River valley; one consisting of the Conondale and D'Aguilar Ranges, and the other of the southern isolates in the Main, Border and Gibraltar Ranges. Sequence divergence between the two regions was more consistent with a late Miocene or Pliocene rather than late Pleistocene separation, and is similar to that found among phylogeographic divisions of rainforest reptiles and amphibians in north Queensland rainforests. The molecular evidence for long-term separation of these two regions is corroborated by the pattern of species turnover in the distributions of species of rainforest-restricted amphibians and reptiles. Bioclimatic modelling suggests that appropriate conditions for L. pearsoniana would have been restricted to isolated refugees in each phylogeographic division under cooler and drier climates, such as predicted for the last glacial maximum. Currently isolated montane areas may have been connected transiently during the past 2000 years. Identification of long-term zoogeographic divisions among southeast Queensland rainforest herpetofauna has important implications for conservation and management. Conservation management of L. pearsoniana should be applied at the scale of major rainforest isolates and the conservation status of the species should be assessed independently north and south of the historical division.

Animals↗
PubMed1998

Molecular population genetics of the red kangaroo (Macropus rufus): mtDNA variation.

The genetic population structure of a large, wide-ranging marsupial, the red kangaroo (Macropus rufus) was assessed using sequence and haplotype frequency data of mitochondrial DNA (mtDNA) from locations across the species range in Australia. Results from sequence data revealed extensive haplotype diversity within the red kangaroo (32/34 sequences were unique). Sequence diversity was distributed within rather than between geographical regions across the species range. Genetic connectivity across the range of the species has therefore been maintained over the long term. On a smaller within-region scale, significant genetic structuring was evident from heterogeneity of haplotype frequencies amongst sampling sites. The geographical scale of panmictic populations differed across the continent with more restricted genetic populations occurring in areas with greater topographic and habitat complexity. We propose that these differences in area of genetic populations are the result of population responses to limiting ecological factors during drought.

Animals↗
PubMed1998

Changes in cortisol secretion during shiftwork: implications for tolerance to shiftwork?

The present study was conducted to determine the size of changes and the time point of those changes in biological rhythms during night-shift and whether they are associated with tolerance to shiftwork. The adrenal hormone cortisol has frequently been investigated in the field of shiftwork since it follows a pronounced circadian variation and has been demonstrated to be affected by night-work. However, studies are restricted with respect to sample size, number of measurements or duration of sampling periods. Therefore, a sample of 24 night-shift workers was investigated in a cardiac emergency unit for seven nights. Saliva samples were collected frequently for determination of cortisol. A total of 28 cortisol measurements in each subject were made in order to decide whether the circadian rhythm changed, and if so at which time point. A clear reversal of circadian function could be observed for the total group (mean cortisol concentrations) after the fifth night. However, inspection of individual patterns revealed that six out of 24 subjects did not change in circadian function. These subjects exhibited lower durations of and less consistency in recovery sleep across the following days after night-work. With respect to personality dimensions a pattern associated with neuroticism can be observed in subjects without appropriate changes in cortisol rhythm. However, owing to the small sample size of non-adapters these results are preliminary and should be replicated with larger samples. The overall relationship between neuroticism and low adaptability has been discussed.

Adaptation, Physiological↗
PubMed1998

Molecular population genetics of the southern elephant seal Mirounga leonina.

Southern elephant seals breed on sub-Antarctic islands and have a circumpolar distribution. We assayed mitochondrial DNA (mtDNA) and nuclear DNA (nDNA) variation in the three main populations in the south Atlantic, south Indian, and south Pacific oceans, and a smaller continental population in South America. Population structure of mtDNA was strong and not consistent with isolation by distance. The nDNA loci, although less informative, were consistent with the mtDNA results. Geographic structure appears to be dominated by historical processes, not contemporary gene flow. Uncorrected levels of nucleotide diversity for mtDNA control region I (2.86%) and nDNA (0.09%) were similar to those in humans and mice. Mutation rates for control region I (75 x 10(-9) substitutions per site per year) and nDNA (1.23 x 10(-9)) were similar to those in other mammals. Female effective population size and total effective population size were roughly equal at approximately 4 x 10(4), indicating a twofold greater rate of drift for mtDNA. Effective breeding sex ratio of four to five females per male was estimated from nucleotide diversity and mutation rates for mtDNA and nDNA, and was much less than behavioral observations would suggest. There was no evidence for selection at any of the assayed loci.

Alleles↗
PubMed1997

Philopatry of male marine turtles inferred from mitochondrial DNA markers.

Recent studies of mitochondrial DNA (mtDNA) variation among marine turtle populations are consistent with the hypothesis that females return to beaches in their natal region to nest as adults. In contrast, less is known about breeding migrations of male marine turtles and whether they too are philopatric to natal regions. Studies of geographic structuring of restriction fragment and microsatellite polymorphisms at anonymous nuclear loci in green turtle (Chelonia mydas) populations indicate that nuclear gene flow is higher than estimates from mtDNA analyses. Regional populations from the northern and southern Great Barrier Reef were distinct for mtDNA but indistinguishable at nuclear loci, whereas the Gulf of Carpentaria (northern Australia) population was distinct for both types of marker. To assess whether this result was due to reduced philopatry of males across the Great Barrier Reef, we determined the mtDNA haplotypes of breeding males at courtship areas for comparison with breeding females from the same three locations. We used a PCR-restriction fragment length polymorphism approach to determine control region haplotypes and designed mismatch primers for the identification of specific haplotypes. The mtDNA haplotype frequencies were not significantly different between males and females at any of the three areas and estimates of Fst among the regions were similar for males and females (Fst = 0.78 and 0.73, respectively). We conclude that breeding males, like females, are philopatric to courtship areas within their natal region. Nuclear gene flow between populations is most likely occurring through matings during migrations of both males and females through nonnatal courtship areas.

Animals↗
PubMed1997

Genetic population structure of the Greater Bilby Macrotis lagotis, a marsupial in decline.

The Greater Bilby has shown a rapid decline in range during this century and now occupies only a small isolated area in south-western Queensland (QLD) and a larger, but mostly low-density area in the north-western deserts of the Northern Territory (NT) and Western Australia (WA). We have examined variation in the control region of mitochondrial DNA (mtDNA) and at nine microsatellite loci in order to investigate the extent of current and historical subdivision across the species range, and to provide a preliminary assessment of genetic structuring and mating system on a finer scale within the QLD population. Both mtDNA and microsatellite loci had substantial variation within and among populations, with mtDNA divergence being greater between QLD and NT than between NT and WA. The QLD population had two unique and divergent mtDNA lineages, but there was no evidence for strong phylogeographical structure across the range. The available evidence suggests that the bilby should be considered as a single Evolutionarily Significant Unit consisting of multiple Management Units. Augmentation of the remnant QLD population from the NT does not appear necessary at this stage, at least not on genetic grounds. Finer-scale analysis of microsatellite variation for two QLD colonies revealed a deficiency of heterozygotes and significantly greater relatedness within than between colonies. However, structuring was observed only for males; relatedness values for females did not depart from those expected under panmixia. Parentage exclusion analysis for one colony allowed the construction of a partial pedigree which indicated strong polygyny, with one male fathering all but one of the eight offspring assigned. The extent to which fine-scale genetic structuring and differences between sexes is due to sex-biased dispersal vs. effects of mating system remain to be determined.

Animals↗
PubMed1997

Geographic structure of mitochondrial and nuclear gene polymorphisms in Australian green turtle populations and male-biased gene flow.

The genetic structure of green turtle (Chelonia mydas) rookeries located around the Australian coast was assessed by (1) comparing the structure found within and among geographic regions, (2) comparing microsatellite loci vs. restriction fragment length polymorphism analyses of anonymous single copy nuclear DNA (ascnDNA) loci, and (3) comparing the structure found at nuclear DNA markers to that of previously analyzed mitochondrial (mtDNA) control region sequences. Significant genetic structure was observed over all regions at both sets of nuclear markers, though the microsatellite data provided greater resolution in identifying significant genetic differences in pairwise tests between regions. Inferences about population structure and migration rates from the microsatellite data varied depending on whether statistics were based on the stepwise mutation or infinite allele model, with the latter being more congruent with geography. Estimated rates of gene flow were generally higher than expected for nuclear DNA (nDNA) in comparison to mtDNA, and this difference was most pronounced in comparisons between the northern and southern Great Barrier Reef (GBR). The genetic data combined with results from physical tagging studies indicate that the lack of nuclear gene divergence through the GBR is likely due to the migration of sGBR turtles through the courtship area of the nGBR population, rather than male-biased dispersal. This example highlights the value of combining comparative studies of molecular variation with ecological data to infer population processes.

Alleles↗
PubMed1997

Evolution of the AT-rich mitochondrial DNA of the root knot nematode, Meloidogyne hapla.

Mitochondrial DNA of the root knot nematode Meloidogyne hapla was investigated for intraspecific diversity and divergence from other parthenogenetic root knot nematodes. A 1,900-bp fragment containing COII, tRNAHis, 16S rRNA, ND3 and Cyt b genes has been cloned and sequenced from one individual and an 1,188-bp region within this region was sequenced from four other Australian isolates. M. hapla mtDNA is more than 80% AT-rich, like other Meloidogyne spp. Nucleotide diversity within M. hapla is some 10-fold higher than across three other parthenogenetic species of root-knot nematode (M. arenaria, M. javanica, and M. incognita), implying an earlier origin for M. hapla. Nucleotide divergence between M. hapla and its congener M. javanica is as great as that between Ascaris suum and Caenorhabditis elegans, members of different nematode subclasses, while amino acid sequence difference between Meloidogyne is more than twice as great. This is interpreted as an AT-bias-induced acceleration of the amino acid substitution rate, over and above saturation of nucleotide divergence in the strongly AT-biased DNA, on three lines of evidence: (1) in conserved blocks in 16S rDNA congeneric Meloidogyne have no more differences than between A. suum and C. elegans; (2) the Meloidogyne lineage has more amino acid changes relative to the Ascaris/Caenorhabditis lineage with respect to four of five outgroups, the exceptional outgroup being the only species (Apis) as AT-rich as Meloidogyne; and (3) between the two Meloidogyne there are more first and second but fewer third codon position changes than between the other nematode species. M. hapla is also found to contain a 102-bp tandem repeat of at least 40 copies; a size, arrangement, and position the same as in M. javanica, but sequence comparisons did not demonstrate homology between the two repeats.

Amino Acid Sequence↗
PubMed1996

Population structure of the yellow-footed rock-wallaby Petrogale xanthopus (Gray, 1854) inferred from mtDNA sequences and microsatellite loci.

The yellow-footed rock-wallaby Petrogale xanthopus is considered to be potentially vulnerable to extinction. This wallaby inhabits naturally disjunct rocky outcrops which could restrict dispersal between populations, but the extent to which that occurs is unknown. Genetic differences between populations were assessed using mitochondrial DNA (control region) sequencing and analysis of variation at four microsatellite loci among three geographically close sites in south-west Queensland (P. x. celeris) and, for mtDNA only, samples from South Australia (P. x. xanthopus) as well. Populations from South Australia and Queensland had phylogenetically distinct mtDNA, supporting the present classification of these two groups as evolutionarily distinct entities. Within Queensland, populations separated by 70 km of unsuitable habitat differed significantly for mtDNA and at microsatellite loci. Populations separated by 10 km of apparently suitable habitat had statistically homogeneous mtDNA, but a significant difference in allele frequency at one microsatellite locus. Tests for Hardy-Weinberg equilibrium and microgeographical variation at microsatellite loci did not detect any substructuring between two wallaby aggregations within a colony encircling a single rock outcrop. Although the present study was limited by small sample sizes at two of the three Queensland locations examined, the genetic results suggest that dispersal between colonies is limited, consistent with an ecological study of dispersal at one of the sites. Considering both the genetic and ecological data, we suggest that management of yellow-footed rock-wallabies should treat each colony as an independent unit and that conservation of the Queensland and South Australian populations as separate entities is warranted.

Alleles↗
PubMed1995

Molecular support for vicariance as a source of diversity in rainforest.

The origin of high diversity in tropical rainforests is attributed to divergence amongst relatively mesic, late Pleistocene refuges. To test this hypothesis we analysed sequence variation within the mitochondrial DNA of populations of six rainforest-dwelling vertebrate species (one lizard and five birds) in the Wet Tropical rainforests of northeastern Australia. Vicariance among historical refuges was indicated by geographically congruent variation across a historical climatic barrier previously predicted by modelling. Sequence divergence across the barrier varied widely, being highest in species with lowest vagility and greatest restriction to rainforest. A high altitude, rainforest-restricted species was exceptional in lacking mtDNA variation. These data support the suggested role of vicariance in promoting evolutionary diversity in rainforests but also indicate variation in the timing of vicariance events, with most speciation or divergence events occurring well before the late Pleistocene. The relation between the amount of molecular divergence and current ecology suggests a sequence of isolation events, perhaps of increasing severity, occurring between the late Tertiary and the late Pleistocene.

Animals↗
PubMed1995

Acute glaucoma and intracranial hypertension in a child on long-term peritoneal dialysis treated with growth hormone.

A 7-year-old boy with end-stage renal disease on long-term peritoneal dialysis is described. The child developed intracranial hypertension and acute glaucoma during therapy with recombinant human growth hormone (rhGH), 18 months after the onset of treatment. Symptoms developed within 1.5 days and required neurosurgical treatment to reduce the intracranial hypertension because of imminent impaction of the cerebellum and brain stem. After ventricular cerebrospinal fluid drainage and cessation of growth hormone, all symptoms of intracranial hypertension and increased intraocular pressure disappeared. To our knowledge this is the first report of intracranial hypertension or hydrocephalus and acute glaucoma during rhGH therapy. Continuous and long-term control of the ophthalmological and neurological status of patients treated with rhGh is indicated.

Acute Disease↗
PubMed1995

Natural atmospherics and occurrence of seizures in six adolescents with epilepsy: a cross correlation study.

As already seen in a former study of 315 epileptic seizures in adults, subsequent investigation of 3333 epileptic seizures in six adolescents revealed a significant increase of the seizure frequency during days with a higher mean frequency of 28 kHz atmospherics, and a decrease during days with a (Baumer apparatus) distinctly higher amount of 10 kHz when compared with the daily mean frequency within the whole period. However, one patient showed an opposite behaviour regarding the correlations of 28 and 10 kHz atmospherics and the mean numbers of seizures.

Adolescent↗
PubMed1995

Conservation and dynamics of microsatellite loci over 300 million years of marine turtle evolution.

Microsatellite loci consisting of (CA)n repetitive arrays were obtained from three species of marine turtle, and primers were designed to test for polymorphism within species and the persistence of microsatellites across species. Homologous loci were found in each test of six marine species within two families (Cheloniidae and Dermochelyidae), as well as in a freshwater species (Emydidae, Trachemys scripta), which indicates a conservation of flanking sequences spanning approximately 300 million years of divergent evolution. The persistence of homologous microsatellites across marine turtles was confirmed by direct sequencing of loci across species and by the discovery of polymorphism in 24 of 30 cross species tests. The conservation of flanking sequences could be due to a slow rate of base substitution in turtle nuclear DNA, as previously reported for mtDNA. In contrast, the presence of up to 25 alleles per locus per species indicates that the replication slippage events responsible for changes in allele length operate as in mammals. Comparisons of alleles among species revealed that alleles of the same length may not be homologous due to mutations within the flanking sequences. Levels of heterozygosity were consistently higher in species from which the primers were designed, which suggests problems with cross-species comparisons of variability. Within species, microsatellite variation between divergent populations was consistent with results from previous mtDNA studies indicating the usefulness of microsatellites for comparing male- versus female-mediated gene flow.

Animals↗
PubMed1994

Extreme population structuring in the threatened ghost bat, Macroderma gigas: evidence from mitochondrial DNA.

The ghost bat, Macroderma gigas, has undergone a major range contraction and is currently restricted around a few, highly disjunct maternity sites. The amount and distribution of mitochondrial DNA (mtDNA) variation within extant populations has been used to assess levels of current and historical maternal gene flow between these populations. An approximately 330 base pair fragment spanning a hypervariable area of the mtDNA control region was amplified and sequenced by using 22 individuals from four current ghost bat populations. The mean sequence diversity of 4.5% between populations was six times higher than that within populations (0.68%), and alleles within populations were monophyletic. Restriction enzyme analysis of amplified products from an additional 100 individuals revealed fixed allelic differences in the distribution of control region genotypes between the four populations. It is suggested that this extreme genetic subdivision is a consequence of long-term female philopatry. For the purposes of management each population should be treated as an independent entity. The depth of the genetic structuring suggests that the isolation of extant populations preceded the historical range contraction.

Alleles↗