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Carruthers, T. J. B., Carter, S. L., Lookingbill, T. R., Florkowski, L. N., Hawkey, J. M., & Dennison, W. C. (2012). A Habitat-Based Framework for Communicating Natural Resource Condition. ISRN Ecology, 2012, 13pp.
Abstract: Progress in achieving desired environmental outcomes needs to be rigorously measured and reported for effective environmental management. Two major challenges in achieving this are, firstly, how to synthesize monitoring data in a meaningful way at appropriate temporal and spatial scales and, secondly, how to present results in a framework that allows for effective communication to resource managers and scientists as well as a broader general audience. This paper presents a habitat framework, developed to assess the natural resource condition of the urban Rock Creek Park (Washington, DC, USA), providing insight on how to improve future assessments. Vegetation and stream GIS layers were used to classify three dominant habitat types, Forest, Wetland, and Artificial-terrestrial. Within Rock Creek Park, Forest habitats were assessed as being in good condition (67% threshold attainment of desired condition), Wetland habitats to be in fair condition (49% attainment), and Artificial-terrestrial habitats to be in degraded condition (26% attainment), resulting in an assessed fair/good condition (60% attainment; weighted by habitat area) for all natural resources in Rock Creek Park. This approach has potential to provide assessment of resource condition for diverse ecosystems and provides a basis for addressing management questions across multiple spatial scales.
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Newton, A., Carruthers, T. J. B., & Icely, J. (2012). The coastal syndromes and hotspots on the coast. Estuar. Coast. Shelf Sci., 96, 39–47.
Abstract: Human intervention has resulted in a number of global and river syndromes that are mirrored by coastal syndromes caused by erosion, subsidence, salinization of aquifers, urbanization, eutrophication, invasive species and over exploitation of natural resources. These problems are now global, with few coastal zones remaining unaffected and pristine. However, the problems are particularly severe at “hotspots” in the coastal zone. These include river-mouth systems where fluxes of water, sediment, fertilizers and contaminants are focused; urbanized coasts and megacities where vulnerable populations are concentrated; Arctic coasts where the effects of climate change are accelerating a fundamental state change; and, at low lying coasts that are at risk of flooding, storm surges, sea-level rise and subsidence such as Micronesian island states where managed realignment and setback is not an option. A range of societal responses and appropriate governance frameworks will be necessary to treat the coastal syndromes. (C) 2011 Elsevier Ltd. All rights reserved.
Keywords: Arctic; river-mouth; Islands; urban coasts; vulnerability; global syndromes
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Taylor, D. R., & Keller, S. R. (2007). Historical range expansion determines the phylogenetic diversity introduced during contemporary species invasion. Evolution, 61(2), 334–345.
Abstract: For a species rapidly expanding its geographic range, such as during biological invasion, most alleles in the introduced range will have their evolutionary origins in the native range. Yet, the way in which historical processes occurring over evolutionary time in the native range contribute to the diversity sampled during contemporary invasion is largely unknown. We used chloroplast DNA (cpDNA) gene genealogies and coalescent methods to study two congeneric plants, Silene latifolia and S. vulgaris. We examined how phylogenetic diversity was shaped by demographic growth and historical range expansions in the native European range, and how this history affected the diversity sampled during their recent invasion of North America. Genealogies from both species depart from neutrality, likely as a result of demographic expansion in the ancestral range, the timing of which corresponds to shortly after each species originated. However, the species differ in the spatial distribution of cpDNA lineages across the native range. Silene latifolia shows a highly significant phylogeographic structure that most likely reflects different avenues of the post-glacial expansion into northern Europe from Mediterranean refugia. By contrast, cpDNA lineages in S. vulgaris have been widely scattered across Europe during, or since, the most recent post-glacial expansion. These different evolutionary histories resulted in dramatic differences in how phylogenetic diversity was sampled during invasion of North America. In S. latifolia, relatively few, discrete invasion events from a structured native range resulted in a rather severe genetic bottleneck, but also opportunities for admixture among previously isolated lineages. In S. vulgaris, lack of genetic structure was accompanied by more representative sampling of phylogenetic diversity during invasion, and reduced potential for admixture. Our results provide clear insights into how historical processes may feed forward to influence the phylogenetic diversity of species invading new geographic ranges.
Keywords: chloroplast DNA; coalescent; invasion; mismatch distribution; phylogeography; range expansion; Silene
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Barr, C. M., Keller, S. R., Ingvarsson, P. K., Sloan, D. B., & Taylor, D. R. (2007). Variation in mutation rate and polymorphism among mitochondrial genes of Silene vulgaris RID G-2748-2010 RID D-4152-2011. Mol. Biol. Evol., 24(8), 1783–1791.
Abstract: The prevailing wisdom of the plant mitochondrial genome is that it has very low substitution rates, thus it is generally assumed that nucleotide diversity within species will also be low. However, recent evidence suggests plant mitochondrial Genes may harbor variable and sometimes high levels of within-species polymorphism, a result attributed to variance in the influence of selection. However, insufficient attention has been paid to the effect of among-gene variation in mutation rate on varying levels of polymorphism across loci. We measured levels of polymorphism in seven mitochondrial gene regions across a geographically wide sample of the plant Silene vulgaris to investigate whether individual mitochondrial genes accumulate polymorphisms equally. We found that Genes vary significantly in polymorphism. Tests based on coalescence theory show that the genes vary significantly in their scaled mutation rate, which, in the absence of differences among genes in effective population size, suggests these genes vary in their underlying mutation rate. Further evidence that among-gene variance in polymorphism is due to variation in the underlying mutation rate comes from a significant positive relationship between the number of segregating sites and silent site divergence from an outgroup. Contrary to recent studies, we found unconvincing evidence of recombination in the mitochondrial genome, and generally confirm the standard model of plant mitochondria characterized by low substitution rates and no recombination. We also show no evidence of significant variation in the strength or direction of selection among genes; this result may be expected if there is no recombination. Tile present study provides some of the most thorough data on plant mitochondrial polymorphism, and provides compelling evidence for mutation rate variation among genes. The study also demonstrates the difficulty in establishing a null model of mitochondrial genome polymorphism, and thus the difficulty. in the absence of a comparative approach, in testing the assumption that low substitution rates in plant mitochondria lead to low polymorphism.
Keywords: plant mitochondria; polymorphism; mutation rate; recombination; Silene vulgaris
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Sloan, D. B., Barr, C. M., Olson, M. S., Keller, S. R., & Taylor, D. R. (2008). Evolutionary rate variation at multiple levels of biological organization in plant mitochondrial DNA RID D-4152-2011. Mol. Biol. Evol., 25(2), 243–246.
Abstract: We examined patterns of mitochondrial polymorphism and divergence in the angiosperm genus Silene and found substantial variation in evolutionary rates among species and among lineages within species. Moreover, we found corresponding differences in the amount of polymorphism within species. We argue that, along with our earlier findings of rate variation among genes, these patterns of rate heterogeneity at multiple phylogenetic scales are most likely explained by differences in underlying mutation rates. In contrast, no rate variation was detected in nuclear or chloroplast loci. We conclude that mutation rate heterogeneity is a characteristic of plant mitochondrial sequence evolution at multiple biological scales and may be a crucial determinant of how much polymorphism is maintained within species. These dramatic patterns of variation raise intriguing questions about the mechanisms driving and maintaining mutation rate heterogeneity in plant mitochondrial genomes. Additionally, they should alter our interpretation of many common phylogenetic and population genetic analyses.
Keywords: molecular clock; mtDNA; mutators; Silene latifolia; Silene noctiflora; Silene vulgaris
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