565 research outputs found
Micro-geographic landscape features demarcate seedling genetic structure in the stream lily, Helmholtzia glaberrima
No full textCopyright © 2007 Elsevier B.V. All rights reserved.Peter J. Prentis and Peter B. Matherhttp://www.elsevier.com/wps/find/journaldescription.cws_home/503303/description#descriptio
Statistical phylogeographic tests of competing 'Lake Carpentaria hypotheses' in the mouth-brooding freshwater fish, Glossamia aprion (Apogonidae)
No full textGlacial cycles during the Pleistocene reduced sea levels and created new land connections in northern Australia, where many currently isolated rivers also became connected via an extensive paleo-lake system, ‘Lake Carpentaria’. However, the most recent period during which populations of freshwater species were connected by gene flow across Lake Carpentaria is debated: various ‘Lake Carpentaria hypotheses’ have been proposed. Here, we used a statistical phylogeographic approach to assess the timing of past population connectivity across the Carpentaria region in the obligate freshwater fish, Glossamia aprion. Results for this species indicate that the most recent period of genetic exchange across the Carpentaria region coincided with the mid- to late Pleistocene, a result shown previously for other freshwater and diadromous species. Based on these findings and published studies for various freshwater, diadromous and marine species, we propose a set of ‘Lake Carpentaria’ hypotheses to explain past population connectivity in aquatic species: (1) strictly freshwater species had widespread gene flow in the mid- to late Pleistocene before the last glacial maximum; (2) marine species were subdivided into eastern and western populations by land during Pleistocene glacial phases; and (3) past connectivity in diadromous species reflects the relative strength of their marine affinity.Benjamin D. Cook, Mark Adams, Peter B. Mather, and Jane M. Hughe
Fine-scale patterns of genetic variation indicate non-equilibrium gene frequency divergence in the stream lily, Helmholtzia glaberrima
No full textThe definitive version is available at www.blackwell-synergy.comSummary1. Helmholtzia glaberrima (Philydraceae) is a rare plant, endemic to streams of the border ranges of Queensland and New South Wales, Australia.2. We used AFLP markers to investigate genetic diversity and patterns of differentiation among 19 populations of H. glaberrima (24 for demographic analyses), and also collected data on the size, distribution and altitude of populations.3. Based on the distribution of populations, altitude significantly influenced the spatial arrangement of H. glaberrima along stream systems, with population size and frequency greatest in upstream habitat.4. Patterns of genetic diversity within populations were not related to population size or distribution. Altitude and genetic diversity were related, with upstream and downstream populations having higher genetic diversity than mid‐stream populations. Differentiation among populations was pronounced at all spatial scales and did not conform to a hierarchical model of gene flow.5. Both genetic diversity and differentiation data sets indicated that strong non‐equilibrium conditions associated with persistent founder effects, and not landscape characteristics, have shaped patterns of genetic diversity and differentiation in H. glaberrima. Patterns of distribution indicate that populations are distributed over a discontinuous ecological gradient, which becomes marginal at lower altitudes.Peter J. Prentis and Peter B. Mathe
Significance of post-germination buoyancy in Helmholtzia glaberrima and Philydrum lanuginosum (Philydraceae)
No full text© CSIRO 2006Post-germination buoyancy has been proposed to reduce seedling establishment in amphibious plants if seeds germinate under flooded conditions. We tested this hypothesis in two amphibious species, Helmholtzia glaberrima (Hook.) and Philydrum lanuginosum (Banks & Sol.). We tested whether seed germination was affected by different levels of inundation, whether seedlings germinating underwater floated and whether seedlings established after prolonged floatation at rates comparable to seedling establishment in waterlogged soil. Germination underwater and in waterlogged soil was similar for both species. Seeds germinating underwater exhibited post-germination buoyancy and established at similar rates to seedlings in waterlogged soil. The results demonstrated that if seeds germinated underwater, post-germination buoyancy conferred the potential to avoid inundation and promote establishment, when waters recede and/or in areas of high soil moisture that are not submerged. More generally, this finding showed that post-germination buoyancy can promote seedling dispersal and the deposition of seedlings in conditions more favourable for establishment if seeds germinate under flooded conditions or in permanent wetlands.Peter J. Prentis, Noel M. Meyers and Peter B. Mathe
Bulletin d'histoire de la culture matérielle #30
No full textArticles: Retrospective analysis of folk history: a Nova Scotian case history by Diane Tye -- The Krug Brothers' furniture factory, Chelsey, Ontario: industrialization and furniture design in the late nineteenth century by Jennifer Trant. -- Technology and textile mill architecture in Canada by A.B. McCullough -- Material history in situ--original furniture at O'Keefe Historic Ranch by Ken Mather -- Research Reports: Musées d'agriculture et recherches sur les anciennes techniques rurales en France par Jean-René Trochet -- Saint Anne's Chapel, Fredericton, New Brunswick: a living exhibit of material culture by Peter Malmberg -- Reviews -- Notes and CommentsThe Material History Bulletin was published 1976-Fall 1990 (nos. 1-32). The name was then changed to the Material History Review, published Spring 1991-Fall 2005 (nos. 33-62). The name changed again to Material Culture Review, Spring 2006 (no. 63)-present. Published semiannually
L-optimal transportation for Ricci flow
No full textWe introduce the notion of L-optimal transportation, and use it to construct a natural monotonic quantity for Ricci flow which includes a selection of other monotonicity results, including some key discoveries of Perelman [13] (both related to entropy and to L-length) and a recent result of McCann and the author [11]
Reconciling geography and genealogy: phylogeography of giant freshwater prawns from the Lake Carpentaria region
No full textThere is convincing geological evidence for the historical existence of an ancient lake on the Australian–New Guinea continental shelf during the late Pleistocene. Lake Carpentaria was a vast fresh- to brackishwater lake that would presumably have provided habitat for, and facilitated gene flow among, aquatic taxa that tolerate low to moderate salinities in this region. Moreover, it has been argued that the outflow of Papua New Guinea's Fly River was diverted westward into Lake Carpentaria during this period, although this hypothesis is controversial. We predicted that these events, if a true history, would have promoted gene flow and population growth via range-expansion events in the giant freshwater prawn (Macrobrachium rosenbergii) and restricted gene flow subsequently by way of a vicariant event as sea levels rose during the late Pleistocene, and a marine environment replaced Lake Carpentaria. We tested these hypotheses using phylogeographical and phylogenetic analyses of mitochondrial DNA variation in M. rosenbergii populations sampled from the Lake Carpentaria region. Our results support the hypothesis that Lake Carpentaria facilitated gene flow among populations of M. rosenbergii that are today isolated, but contest claims of a westward diversion of the Fly River. We inferred the timing of initial expansion in the ‘Lake Carpentaria lineage’ and found the timing of this event to be broadly concordant with geological dating of the formation of Lake Carpentaria. Reconciling geological and molecular data, as presented here, provides a powerful framework for investigating the influence of historical earth history events on the distribution of biological (i.e. molecular) diversity
Comparative analysis of gill transcriptomes of two freshwater crayfish, Cherax cainii and C. destructor
No full textWe undertook deep sequencing of gill transcriptomes from two freshwater crayfish, Cherax cainii and Cherax destructor, in order to generate genomic resources for future genomics research. Over 83 and 100 million high quality (quality score (Q) ≥ 30) paired-end Illumina reads (150 bp) were assembled into 147,101 and 136,622 contigs in C. cainii and C. destructor, respectively. A total of 24,630 and 23,623 contigs received significant BLASTx hits and allowed the identification of multiple gill expressed candidate genes associated with pH and salinity balance. These functionally annotated transcripts will provide a resource to facilitate comparative genomic research in the genus Cherax, and in particular allow insights into respiratory and osmoregulatory physiology of this group of animals
A comparative study of cellulase and xylanase activity\ud in freshwater crayfish and marine prawns
No full textCellulase and xylanase digestive enzyme activities were compared in four freshwater crayfish (Genus Cherax) and three marine prawn (Genus Penaeus) species.Temperature and pH profiles for cellulase (endoglucanase)were found to be very similar in all species,\ud
with maximum activity occurring at 60oC and pH 5.0.Temperature and pH profiles for xylanase (endoxylanase)were also very similar in all cray¢sh species,with maximum activity occurring at 50oC and pH 5.0. Xylanase activity was not detected in the\ud
three prawn species examined. In addition, in vitro studies showed thatmost species were able to liberate glucose from carboxymethyl cellulose, indicating that cellulose substrates can be a source of energy for both crayfish and prawn species
Habitat heterogeneity influences connectivity in a spatially structured pest population
No full text1. Patterns of connectivity influence pest population system dynamics, and it is essential to consider connectivity when planning effective management strategies. Traditional connectivity models often consider populations embedded in a matrix of unsuitable habitat. This approach is unlikely to be applicable to those pest species that can utilize most of the landscape in which they live. There is therefore a need for a simple and flexible tool to assess connectivity in such systems.\ud
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2. In this study, we developed a new model in which contiguous resource patches that differ in quality, and landscape elements that impede dispersal, impact on connectivity within a population system. The model was applied to a wild rabbit population system, a well-studied pest species in Australia. An independent population genetic data set was used to validate the model.\ud
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3. There was a highly significant association between pairwise population connectivity and the genetic data (Mantel test, r=−0·502, P= 0·002). As predicted, two populations that showed very low connectivity were strongly isolated genetically. These sites appeared to be substantially isolated because of forests, which acted to impede rabbit dispersal. When these sites were excluded from analysis, connectivity indices again explained the pattern of genetic data (Mantel test, r=−0·46, P= 0·037). This showed that both spatial variation in resource quality and forests influenced connectivity in this system. Sensitivity analyses confirmed that the distribution and extent of forests was important in limiting connectivity to some sites. The model was relatively robust to changes in population parameters.\ud
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4. Synthesis and applications. Connectivity among wild rabbit populations in this system was strongly influenced by habitat heterogeneity, rather than factors such as geographical distance or major landscape elements such as rivers, both of which are traditionally considered to influence system dynamics. This may have substantial implications for many pest systems, and suggests that the impact of habitat heterogeneity on connectivity should be considered when planning efficient management strategies
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