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Renfroe Farms, a family business with David, Don, Kevin Renfroe and Kim Renfroe-Johnson harvest corn, part of their operation that focuses on utilizing conservation practices developed with the U.S. Department of Agriculture (USDA) Farm Production and Conservation (FPAC) Natural Resources Conservation Service (NRCS) to balance land stewardship and production in Carroll County, TN, on Sept 18, 2019.
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Generic Indicators for Loss of Resilience Before a Tipping Point Leading to Population Collapse
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Theory predicts that the approach of catastrophic thresholds in natural systems (e.g., ecosystems,
the climate) may result in an increasingly slow recovery from small perturbations, a phenomenon
called critical slowing down. We used replicate laboratory populations of the budding yeast
Saccharomyces cerevisiae for direct observation of critical slowing down before population
collapse. We mapped the bifurcation diagram experimentally and found that the populations
became more vulnerable to disturbance closer to the tipping point. Fluctuations of population
density increased in size and duration near the tipping point, in agreement with the theory.
Our results suggest that indicators of critical slowing down can provide advance warning of
catastrophic thresholds and loss of resilience in a variety of dynamical systems.
SCIENCE VOL 336 1
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Climate Science Documents
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Genetic change for earlier migration timing in a pink salmon population
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To predict how climate change will influence populations, it is necessary to understand the mechanisms, particularly microevolution and phenotypic plasticity, that allow populations to persist in novel environmental conditions. Although evidence for climate-induced phenotypic change in populations is widespread, evidence documenting that these phenotypic changes are due to microevolution is exceed- ingly rare. In this study, we use 32 years of genetic data (17 complete generations) to determine whether there has been a genetic change towards earlier migration timing in a population of pink salmon that shows phenotypic change; average migration time occurs nearly two weeks earlier than it did 40 years ago. Experimental genetic data support the hypothesis that there has been directional selection for earlier migration timing, resulting in a substantial decrease in the late-migrating phenotype (from more than 30% to less than 10% of the total abundance). From 1983 to 2011, there was a significant decrease—over threefold—in the frequency of a genetic marker for late-migration timing, but there were minimal changes in allele frequencies at other neutral loci. These results demonstrate that there has been rapid microevolution for earlier migration timing in this population. Circadian rhythm genes, however, did not show any evidence for selective changes from 1993 to 2009.
Keywords: microevolution; genetic change; salmon; circadian rhythms; climate change; migration timing
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Genetic consequences of climate change for northern plants
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Climate change will lead to loss of range for many species, and thus to loss of genetic diversity crucial for their long-term persistence. We analysed range-wide genetic diversity (amplified fragment length poly- morphisms) in 9581 samples from 1200 populations of 27 northern plant species, to assess genetic consequences of range reduction and potential association with species traits. We used species distri- bution modelling (SDM, eight techniques, two global circulation models and two emission scenarios) to predict loss of range and genetic diversity by 2080. Loss of genetic diversity varied considerably among species, and this variation could be explained by dispersal adaptation (up to 57%) and by genetic differentiation among populations (FST; up to 61%). Herbs lacking adaptations for long-distance disper- sal were estimated to lose genetic diversity at higher rate than dwarf shrubs adapted to long-distance dispersal. The expected range reduction in these 27 northern species was larger than reported for tem- perate plants, and all were predicted to lose genetic diversity according to at least one scenario. SDM combined with FST estimates and/or with species trait information thus allows the prediction of species’ vulnerability to climate change, aiding rational prioritization of conservation efforts.
Keywords: conservation genetics; FST; genetic diversity; range reduction; species distribution model; species traits
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Genetic diversity in widespread species is not congruent with species richness in alpine plant communities
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The Convention on Biological Diversity (CBD) aims at the conservation of all three levels of biodiversity, that is, ecosystems, species and genes. Genetic diversity represents evolutionary potential and is important for ecosystem functioning. Unfortunately, genetic diversity in natural populations is hardly considered in conservation strategies because it is difficult to measure and has been hypothesised to co-vary with species richness. This means that species richness is taken as a surrogate of genetic diversity in conservation plan- ning, though their relationship has not been properly evaluated. We tested whether the genetic and species levels of biodiversity co-vary, using a large-scale and multi-species approach. We chose the high-mountain flora of the Alps and the Carpathians as study systems and demonstrate that species richness and genetic diversity are not correlated. Species richness thus cannot act as a surrogate for genetic diversity. Our results have important consequences for implementing the CBD when designing conservation strategies.
Keywords
alpine vascular plants, Alps, biodiversity conservation, Carpathians, genetic diversity, species richness.
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Genetic signatures of a demographic collapse in a large-bodied forest dwelling primate
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It is difficult to predict how current climate change will affect wildlife species adapted to a tropical rainforest environment. Understanding how population dynamics fluctuated in such species throughout periods of past climatic change can provide insight into this issue. The drill (Mandrillus leucophaeus) is a large-bodied rainforest adapted mammal found in West Central Africa. In the middle of this endangered monkey’s geographic range is Lake Barombi Mbo, which has a well-documented palynological record of environmental change that dates to the Late Pleistocene. We used a Bayesian coalescent-based framework to analyze 2,076 base pairs of mitochondrial DNA across wild drill populations to infer past changes in female effective population size since the Late Pleistocene. Our results suggest that the drill underwent a nearly 15-fold demographic collapse in female effective population size that was most prominent during the Mid Holocene (approximately 3-5 Ka). This time period coincides with a period of increased dryness and seasonality across Africa and a dramatic reduction in forest coverage at Lake Barombi Mbo. We believe that these changes in climate and forest coverage were the driving forces behind the drill population decline. Furthermore, the warm temperatures and increased aridity of the Mid Holocene are potentially analogous to current and future conditions faced by many tropical rainforest communities. In order to prevent future declines in population size in rainforest-adapted species such as the drill, large tracts of forest should be protected to both preserve habitat and prevent forest loss through aridification. Bayesian Skyline Plot, bottleneck, climate change, Cross-Sanaga-Bioko forests, drill, Mandrillus.
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Genome diversity in wild grasses under environmental stress
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Patterns of diversity distribution in the Isa defense locus in wild- barley populations suggest adaptive selection at this locus. The extent to which environmental selection may act at additional nuclear-encoded defense loci and within the whole chloroplast genome has now been examined by analyses in two grass species. Analysis of genetic diversity in wild barley (Hordeum spontaneum) defense genes revealed much greater variation in biotic stress-related genes than abiotic stress-related genes. Genetic diversity at the Isa defense locus in wild populations of weeping ricegrass [Microlaena stipoides (Labill.) R. Br.], a very distant wild-rice relative, was more diverse in samples from relatively hotter and drier environments, a phenomenon that reflects observations in wild barley populations. Whole-chloroplast genome sequences of bulked weeping ricegrass individuals sourced from contrasting environments showed higher levels of diversity in the drier environment in both coding and noncoding portions of the genome. Increased genetic diversity may be important in allowing plant populations to adapt to greater environmental variation in warmer and drier climatic conditions.
adaptive variation | genomics | molecular evolution | disease resistance | abiotic stress resistance
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Gentner Hopkins 1966.pdf
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FIN-GEN
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George Benz Aquatic Ecology Fellowship at Tennessee Aquarium
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The Tennessee Aquarium is now taking applications for the George Benz Aquatic Ecology Fellowship.
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Gerhesich 1981.pdf
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FIN-GEN
