Browsing by Subject "Population dynamics"

Now showing 1 - 3 of 3
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    Ancient genomes indicate population replacement in Early Neolithic Britain
    (Springer Nature, 2019-05) Brace, Selina; Diekmann, Yoan; Booth, Thomas J.; van Dorp, Lucy; Faltyskova, Zuzana; Rohland, Nadin; Mallick, Swapan; Olalde, Iñigo; Ferry, Matthew; Michel, Megan; Oppenheimer, Jonas; Broomandkhoshbacht, Nasreen; Stewardson, Kristin; Martiniano, Rui; Walsh, Susan; Kayser, Manfred; Charlton, Sophy; Hellenthal, Garrett; Armit, Ian; Schulting, Rick; Craig, Oliver E.; Sheridan, Alison; Parker Pearson, Mike; Stringer, Chris; Reich, David; Thomas, Mark G.; Barnes, Ian; Biology, School of Science
    The roles of migration, admixture and acculturation in the European transition to farming have been debated for over 100 years. Genome-wide ancient DNA studies indicate predominantly Aegean ancestry for continental Neolithic farmers, but also variable admixture with local Mesolithic hunter-gatherers. Neolithic cultures first appear in Britain circa 4000 BC, a millennium after they appeared in adjacent areas of continental Europe. The pattern and process of this delayed British Neolithic transition remain unclear. We assembled genome-wide data from 6 Mesolithic and 67 Neolithic individuals found in Britain, dating 8500-2500 BC. Our analyses reveal persistent genetic affinities between Mesolithic British and Western European hunter-gatherers. We find overwhelming support for agriculture being introduced to Britain by incoming continental farmers, with small, geographically structured levels of hunter-gatherer ancestry. Unlike other European Neolithic populations, we detect no resurgence of hunter-gatherer ancestry at any time during the Neolithic in Britain. Genetic affinities with Iberian Neolithic individuals indicate that British Neolithic people were mostly descended from Aegean farmers who followed the Mediterranean route of dispersal. We also infer considerable variation in pigmentation levels in Europe by circa 6000 BC.
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    Climatic and geographic predictors of life history variation in Eastern Massasauga (Sistrurus catenatus): A range-wide synthesis
    (Plos, 2017-02-14) Hileman, Eric T.; King, Richard B.; Adamski, John M.; Anton, Thomas G.; Bailey, Robyn L.; Baker, Sarah J.; Bieser, Nickolas D.; Bell Jr., Thomas A.; Bissell, Kristin M.; Bradke, Danielle R.; Campa III, Henry; Casper, Gary S.; Cedar, Karen; Cross, Matthew D.; DeGregorio, Brett A.; Dreslik, Michael J.; Faust, Lisa J.; Harvey, Daniel S.; Hay, Robert W.; Jellen, Benjamin C.; Johnson, Brent D.; Johnson, Glenn; Kiel, Brooke D.; Kingsbury, Bruce A.; Kowalski, Matthew J.; Lee, Yu Man; Lentini, Andrew M.; Marshall, John C.; Mauger, David; Moore, Jennifer A.; Paloski, Rori A.; Phillips, Christopher A.; Pratt, Paul D.; Preney, Thomas; Prior, Kent A.; Promaine, Andrew; Redmer, Michael; Reinert, Howard K.; Rouse, Jeremy D.; Shoemaker, Kevin T.; Sutton, Scott; VanDeWalle, Terry J.; Weatherhead, Patrick J.; Wynn, Doug; Yagi, Anne; Department of Biology, School of Science
    Elucidating how life history traits vary geographically is important to understanding variation in population dynamics. Because many aspects of ectotherm life history are climate-dependent, geographic variation in climate is expected to have a large impact on population dynamics through effects on annual survival, body size, growth rate, age at first reproduction, size-fecundity relationship, and reproductive frequency. The Eastern Massasauga (Sistrurus catenatus) is a small, imperiled North American rattlesnake with a distribution centered on the Great Lakes region, where lake effects strongly influence local conditions. To address Eastern Massasauga life history data gaps, we compiled data from 47 study sites representing 38 counties across the range. We used multimodel inference and general linear models with geographic coordinates and annual climate normals as explanatory variables to clarify patterns of variation in life history traits. We found strong evidence for geographic variation in six of nine life history variables. Adult female snout-vent length and neonate mass increased with increasing mean annual precipitation. Litter size decreased with increasing mean temperature, and the size-fecundity relationship and growth prior to first hibernation both increased with increasing latitude. The proportion of gravid females also increased with increasing latitude, but this relationship may be the result of geographically varying detection bias. Our results provide insights into ectotherm life history variation and fill critical data gaps, which will inform Eastern Massasauga conservation efforts by improving biological realism for models of population viability and climate change.
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    Persistence as an Optimal Hedging Strategy
    (Elsevier, 2021) Browning, Alexander P.; Sharp, Jesse A.; Mapder, Tarunendu; Baker, Christopher M.; Burrage, Kevin; Simpson, Matthew J.; Medicine, School of Medicine
    Bacteria invest in a slow-growing subpopulation, called persisters, to ensure survival in the face of uncertainty. This hedging strategy is remarkably similar to financial hedging, where diversifying an investment portfolio protects against economic uncertainty. We provide a new, to our knowledge, theoretical foundation for understanding cellular hedging by unifying the study of biological population dynamics and the mathematics of financial risk management through optimal control theory. Motivated by the widely accepted role of volatility in the emergence of persistence, we consider several models of environmental volatility described by continuous-time stochastic processes. This allows us to study an emergent cellular hedging strategy that maximizes the expected per capita growth rate of the population. Analytical and simulation results probe the optimal persister strategy, revealing results that are consistent with experimental observations and suggest new opportunities for experimental investigation and design. Overall, we provide a new, to our knowledge, way of conceptualizing and modeling cellular decision making in volatile environments by explicitly unifying theory from mathematical biology and finance.