Reintroductions of rare plants require detailed knowledge of habitat requirements, species interactions,and restoration techniques. Thus, incremental experimentation over many years may be required to develop adequate...Reintroductions of rare plants require detailed knowledge of habitat requirements, species interactions,and restoration techniques. Thus, incremental experimentation over many years may be required to develop adequate knowledge and techniques for successful reintroduction. To determine drivers of extinction in historical reintroductions of a federally endangered perennial(Astragalus bibullatus), we developed a reintroduction experiment to disentangle the relative importance of habitat quality, herbivores, and restoration technique on reintroduction success. In a factorial design, we manipulated access to vertebrate herbivores across different habitat types(mesic ecotone vs. xeric barren), and used founder populations comprised of more transplants and genetic sources than previous reintroduction attempts.In mesic ecotones where historical reintroductions failed, excluding herbivores, thinning woody encroachment to improve habitat quality, outplanting across a greater array of microhabitats, and increasing founder population size did not improve demographic rates over previous attempts.Compared to mesic ecotones, transplant survival rates and cumulative fruit production were more than two and ten times greater, respectively, in a xeric barren ecotone characterized by open, grassy, and dry microenvironmental conditions. Across all sites, herbivores decreased probabilities of survival and flowering of larger adult plants. Flowering rates were 80% greater inside relative to outside herbivore exclusion cages. Over a four-year period, only a single uncaged plant produced fruit. Our study demonstrates that habitat quality and vertebrate herbivory are key drivers of long-term persistence in rare plant reintroductions. Using incremental experiments that build on previous knowledge gained from long-term monitoring can improve reintroduction outcomes.展开更多
Genetic changes over space and time provide insights into the relative roles of evolutionary factors in shaping genetic patterns within plant populations. However, compared with spatial genetic structure, few studies ...Genetic changes over space and time provide insights into the relative roles of evolutionary factors in shaping genetic patterns within plant populations. However, compared with spatial genetic structure, few studies have been conducted on genetic changes over time. In this study, we used six polymorphic microsatellite loci to assess genetic variation of six size-classes of the population of Liushan, Cryptomeriajaponica var. sinensis, in the Tianmushan National Nature Reserve, whose origin was debatable. The mean number of alleles per locus and expected heterozygosity were 4.583 and 0.5999 respectively, lower than other conifers with the same life history characteristics. FST was 0.0024-0.003, and the pairwise test revealed no significant differentiation in any pair of size classes. Significant heterozygosity excesses were detected in five size classes except the oldest one, indicating bottleneck event（s）. The above results support the hypothesis that Tianmushan population was introduced and followed by natural regeneration.展开更多
基金supported by the United States Department of Interior National Park Service Challenge Cost-Share Program (Grant: H55901000010)the Tennessee Department of Environment and Conservation-Division of Natural Areas (Grants: 32701-00385, 32701-0899, and 32701-01236)
文摘Reintroductions of rare plants require detailed knowledge of habitat requirements, species interactions,and restoration techniques. Thus, incremental experimentation over many years may be required to develop adequate knowledge and techniques for successful reintroduction. To determine drivers of extinction in historical reintroductions of a federally endangered perennial(Astragalus bibullatus), we developed a reintroduction experiment to disentangle the relative importance of habitat quality, herbivores, and restoration technique on reintroduction success. In a factorial design, we manipulated access to vertebrate herbivores across different habitat types(mesic ecotone vs. xeric barren), and used founder populations comprised of more transplants and genetic sources than previous reintroduction attempts.In mesic ecotones where historical reintroductions failed, excluding herbivores, thinning woody encroachment to improve habitat quality, outplanting across a greater array of microhabitats, and increasing founder population size did not improve demographic rates over previous attempts.Compared to mesic ecotones, transplant survival rates and cumulative fruit production were more than two and ten times greater, respectively, in a xeric barren ecotone characterized by open, grassy, and dry microenvironmental conditions. Across all sites, herbivores decreased probabilities of survival and flowering of larger adult plants. Flowering rates were 80% greater inside relative to outside herbivore exclusion cages. Over a four-year period, only a single uncaged plant produced fruit. Our study demonstrates that habitat quality and vertebrate herbivory are key drivers of long-term persistence in rare plant reintroductions. Using incremental experiments that build on previous knowledge gained from long-term monitoring can improve reintroduction outcomes.
基金the Program for New Century Excellent Talents in University (NCET-05-0431)funding from the Commission of Science and Technol-ogy of Lin'an City to XY Chen
文摘Genetic changes over space and time provide insights into the relative roles of evolutionary factors in shaping genetic patterns within plant populations. However, compared with spatial genetic structure, few studies have been conducted on genetic changes over time. In this study, we used six polymorphic microsatellite loci to assess genetic variation of six size-classes of the population of Liushan, Cryptomeriajaponica var. sinensis, in the Tianmushan National Nature Reserve, whose origin was debatable. The mean number of alleles per locus and expected heterozygosity were 4.583 and 0.5999 respectively, lower than other conifers with the same life history characteristics. FST was 0.0024-0.003, and the pairwise test revealed no significant differentiation in any pair of size classes. Significant heterozygosity excesses were detected in five size classes except the oldest one, indicating bottleneck event（s）. The above results support the hypothesis that Tianmushan population was introduced and followed by natural regeneration.
