Article Abstract:
The population dynamics of Rorippa columbiae, a threatened plant species, have been studied on Pierce Island, Washington, through use of viability analysis. Managing rare species to conserve them often requires making decisions based on existing inadequate sets of data. It is important to maintain multiple working hypotheses related to controls of population growth when looking at population trends from limited data. For the Washington study, a number of hypotheses were developed. Importance of density dependence and spatial heterogeneity could not be determined. Models which used and did not use spatial heterogeneity brought very different predictions. It would be valuable to have data on ecological differences among sites and correlates of population vigor. The island is protected, partly because R. columbiae is there, but density for the plant seems to have gone down after the preserve was set up.
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Article Abstract:
Research on prairie phlox indicates that genetic stresses do not always lead to developmental instability. Since fragmentation often results in inbreeding, researchers posited that smaller populations would exhibit greater levels of instability. Instead, certain larger populations showed greater instability, suggesting that developmental mechanisms outside genetics are also responsible for instability.
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Article Abstract:
Results show that population size and number of capsules matured per ramet are significantly correlated and the capsule production is determined at the pollination stage. Data further indicate that to keep Phlox population viable, a population of at least 1000-2000 flowering ramets are needed.
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