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C Moritz

Publications and source records attributed to C Moritz.

At least 19 recordsLinked to original sources
PubMed2000

A molecular phylogeny for the frog genus Limnodynastes (Anura: myobatrachidae).

Members of the genus Limnodynastes are a prominent and widespread feature of the Australian frog fauna. Yet despite their potential to be informative about biogeographic history and mechanisms of speciation, the relationships among these taxa are not well known. We investigated phylogenetic relationships within the genus Limnodynastes via sequencing of mitochondrial (mt)DNA from current members of the genus Limnodynastes and the monotypic genus Megistolotis. a 450-bp fragment of the 16S rRNA gene and a 370-bp fragment of the protein-coding gene ND4 were used to infer a molecular phylogeny. We revise traditional species groupings and now recognize four species groups within Limnodynastes: the L. ornatus group (L. ornatus and L. spenceri), the L. peronii group (L. peronii, L. tasmaniensis, L. fletcheri, the L. depressus), the L. salmini group (L. salmini, L. convexiusculus, and L. lignarius), and the L. dorsalis group (L. dorsalis, L. terraereginae, L. dumerilii and L. interioris). The L. ornatus species group forms a highly distinctive clade that is a sister group to the other Limnodynastes groups. Pending broader phylogenetic studies it could be removed from the genus Limnodynastes. Our results concur with previous suggestions that Megistolotis lignarius is nested within Limnodynastes, and we therefore reclassify this species as Limnodynastes lignarius. Furthermore, specimens identified as L. depressus form a mtDNA lineage distinct from other species in the genus, confirming the validity of the species. Specimens of species from the L. dorsalis group (L. dorsalis, L. dumerilii, L. interioris, and L. terraereginae) are closely related such that L. dumerilii is paraphyletic with two other species. Finally, our study provides broad support for previous phylogenies based on microcomplement fixation.

Animals↗
PubMed2000

Intraspecific phylogeography in the sedge frog Litoria fallax (Hylidae) indicates pre-Pleistocene vicariance of an open forest species from eastern Australia.

The eastern sedge frog Litoria fallax (Anura: Hylidae) is common throughout the open forests and coastal wetlands along the eastern coast of Australia. Its range spans four biogeographical zones from northern Queensland to central New South Wales. Phylogenetic analysis of mitochondrial DNA (mtDNA) haplotypes of 87 L. fallax individuals from 22 populations identified two major mtDNA lineages, differing by 11-12% sequence divergence. The two clades of haplotypes were separated by the McPherson Range, indicating that this mesic upland area has acted as a major long-term barrier to gene flow for this open forest species. Slight isolation by distance was observed within both the northern and southern lineages but was insufficient to explain the large sequence divergence between lineages. Within the northern lineage, additional phylogeographical structure was observed across the relatively dry Burdekin Gap which separates Atherton populations from all populations in the central and eastern Queensland biogeographical zones. There was less phylogeographical structure in the southern lineage suggesting historical gene flow across the drier portions of the Great Dividing Range. These data, together with recent observations of deep phylogeographical divergences in rainforest-restricted Litoria suggest that the east coast hylids of Australia represent an old (Tertiary) radiation. Individual species of Litoria have been strongly affected by climatic and ecological barriers to gene flow during the Quaternary.

Animals↗
PubMed2000

Functional connectivity in the thalamus and hippocampus studied with functional MR imaging.

BACKGROUND AND PURPOSE: With functional connectivity functional MR imaging, co-variance in signal intensity has been shown in functionally related regions of brain in participants instructed to perform no cognitive task. These changes are thought to represent synchronous fluctuations in blood flow, which imply neuronal connections between the regions. The purpose of this study was to map functional connectivity in subcortical nuclei with functional connectivity functional MR imaging. METHODS: Imaging data were acquired with an echo-planar sequence from six volunteers who performed no specific cognitive task. For functional connectivity functional MR imaging, a "seed" voxel or group of voxels was selected from the resting data set in the thalamus or in the hippocampus. Control voxels in gray matter presumed not to be eloquent cortex were also chosen. The correlation coefficient of the seed voxels and the control voxels with every other voxel in the resting data set was calculated. The voxels with correlation coefficients greater than or equal to 0.5 were mapped onto anatomic images for the functional connectivity functional MR images. The anatomic location of these voxels was determined by conventional parcellation methods. RESULTS: For each participant, functional connectivity functional MR imaging maps based on four seed voxels in the thalamus or hippocampus showed clusters of voxels in the ipsilateral and contralateral thalamus or hippocampus. For control voxels, few voxels in the hippocampus or thalamus showed significant correlation. Significantly more pixels in the ipsilateral hippocampus correlated with the seed voxel than in the contralateral hippocampus. The differences between numbers of functionally connected voxels in ipsilateral thalamus and those in contralateral thalamus were not significant. CONCLUSIONS: The thalamus and hippocampus show functional connectivity, presumably representing synchronous changes in blood flow.

Adult↗
PubMed1999

A test of alternative models of diversification in tropical rainforests: ecological gradients vs. rainforest refugia.

Comparison of mitochondrial and morphological divergence in eight populations of a widespread leaf-litter skink is used to determine the relative importance of geographic isolation and natural selection in generating phenotypic diversity in the Wet Tropics Rainforest region of Australia. The populations occur in two geographically isolated regions, and within each region, in two different habitats (closed rainforest and tall open forest) that span a well characterized ecological gradient. Morphological differences among ancient geographic isolates (separated for several million years, judging by their mitochondrial DNA sequence divergence) were slight, but morphological and life history differences among habitats were large and occurred despite moderate to high levels of mitochondrial gene flow. A field experiment identified avian predation as one potential agent of natural selection. These results indicate that natural selection operating across ecological gradients can be more important than geographic isolation in similar habitats in generating phenotypic diversity. In addition, our results indicate that selection is sufficiently strong to overcome the homogenizing effects of gene flow, a necessary first step toward speciation in continuously distributed populations. Because ecological gradients may be a source of evolutionary novelty, and perhaps new species, their conservation warrants greater attention. This is particularly true in tropical regions, where most reserves do not include ecological gradients and transitional habitats.

Animals↗
PubMed1999

Cyclooxygenase-2 inhibition by rofecoxib reverses naturally occurring fever in humans.

Cyclooxygenase (COX) exists as constitutive (COX-1) and inducible (COX-2) isoforms. Nonsteroidal antiinflammatory drugs (NSAIDs) such as ibuprofen and diclofenac inhibit both COX-1 and COX-2. The role of COX-2 in the genesis of fever in monkeys and humans was examined with use of the specific COX-2 inhibitor rofecoxib. Rofecoxib was administered to monkeys made febrile by 6 microg/kg intravenous lipopolysaccharide. Induced pyrexia was followed by oral rofecoxib (1 or 3 mg/kg), diclofenac (3 mg/kg), or vehicle. Rofecoxib and diclofenac rapidly reversed the elevated temperature (P < .05 versus vehicle for 3 mg/kg rofecoxib and diclofenac at 70 to 90 minutes after dosing). A single-dose, parallel-group, double-blind randomized trial was conducted in 94 patients with fever caused by a viral-type illness. Mean baseline temperature was similar for all groups (-38.5 degrees C). Patients received oral doses of 12.5 mg rofecoxib, 25 mg rofecoxib, 400 mg ibuprofen, or placebo and the mean +/- SE change in oral temperature at 4 hours after dosing was -0.97 degrees C +/- 0.11 degrees C, -1.19 degrees C +/- 0.09 degrees C, -1.20 degrees C +/- 0.11 degrees C, and 0.01 C +/- 0.17 C, respectively (P < .001 for active treatments versus placebo). Specific inhibition of COX-2 by rofecoxib results in antipyretic activity in monkeys and humans comparable to dual COX-1/COX-2 inhibitors such as diclofenac or ibuprofen. The data support the hypothesis that it is the COX-2 isoform that is primarily involved in the genesis of fever in humans.

Administration, Oral↗
PubMed1999

Mitochondrial DNA sequence variation within the remnant populations of the endangered numbat (Marsupialia: Myrmecobiidae: Myrmecobius fasciatus).

The numbat has been reduced to two populations in Western Australia. To better understand the effects of range reduction on gene flow and genetic variation, and to address questions crucial for the species' management, we analysed mitochondrial DNA (mtDNA) sequences of free-ranging individuals and museum specimens. The results suggest recent connectivity between the remnant populations, although one of those may have lost significant amounts of genetic diversity during the recent population size reduction. We propose that for management purposes the remnant populations should be treated as a single historical lineage and that, subject to certain caveats, consideration should be given to population augmentation by translocation.

Animals↗
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↗