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排序方式: 共有2216条查询结果,搜索用时 15 毫秒
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Sean A. Parks Carlos Carroll Solomon Z. Dobrowski Brady W. Allred 《Global Change Biology》2020,26(5):2944-2955
Climate connectivity, the ability of a landscape to promote or hinder the movement of organisms in response to a changing climate, is contingent on multiple factors including the distance organisms need to move to track suitable climate over time (i.e. climate velocity) and the resistance they experience along such routes. An additional consideration which has received less attention is that human land uses increase resistance to movement or alter movement routes and thus influence climate connectivity. Here we evaluate the influence of human land uses on climate connectivity across North America by comparing two climate connectivity scenarios, one considering climate change in isolation and the other considering climate change and human land uses. In doing so, we introduce a novel metric of climate connectivity, ‘human exposure’, that quantifies the cumulative exposure to human activities that organisms may encounter as they shift their ranges in response to climate change. We also delineate potential movement routes and evaluate whether the protected area network supports movement corridors better than non‐protected lands. We found that when incorporating human land uses, climate connectivity decreased; climate velocity increased on average by 0.3 km/year and cumulative climatic resistance increased for ~83% of the continent. Moreover, ~96% of movement routes in North America must contend with human land uses to some degree. In the scenario that evaluated climate change in isolation, we found that protected areas do not support climate corridors at a higher rate than non‐protected lands across North America. However, variability is evident, as many ecoregions contain protected areas that exhibit both more and less representation of climate corridors compared to non‐protected lands. Overall, our study indicates that previous evaluations of climate connectivity underestimate climate change exposure because they do not account for human impacts. 相似文献
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Females of Zeiraphera canadensis Mut. & Free., the spruce bud moth, were reared in the laboratory at constant and alternating temperatures, and in an outdoor insectary, to (1) determine the effects of temperature, age and size on several reproductive parameters and, (2) to test the hypothesis that body size-temperature interactions influence longevity and realized fecundity. Egg maturation was linearly related to age and large moths developed eggs at a higher rate than small ones. Mcan lifetime oviposition rate reached a maximum and remained stable at temperatures 20° C while the mean lifetime rate of egg maturation increased linearly with temperature, indicating that higher temperatures adversely affect oviposition. The production of nonviable eggs increased with age but also with temperature, suggesting high temperature (25° C) reduces egg quality and/or hinders fertilization. The realized fecundity and longevity of females reared under an alternating temperature regime (mean 20° C) was significantly less than that of females reared at constant 20° C. Similar realized fecundity, longevity and mean lifetime oviposition rates for females reared at temperatures alternating between 10 and 25° C (mean 20° C) and those at constant 25° C reflected the inability of females to recover from elevated diurnal temperatures. Longevity was positively related to female body size at constant 15 and 20° C but the relationships were negative for moths exposed to diurnal temperatures equal to or exceeding 25° C. Due to the reduced longevity of large moths at high temperatures, linear regressions between size and realized fecundity were only significant at constant temperatures 20° C. At higher temperatures, the size-fecundity relationship became curvilinear as a result of the diminished reproductive output of large individuals. Reduced fecundity and longevity of large females at high temperatures may have been due to elevated internal temperatures of large-bodied moths. Large females in a controlled-environment chamber maintained at 25° C developed an internal temperature excess (i.e. temperature above ambient) of nearly 2° C while small-bodied females exceeded ambient by only 0.3° C. However, when held at 20° C, the temperature excess of large-bodied moths was much less than 1° C and small-bodied females did not differ from ambient. Such interactions between temperature and body size suggest that there should be stabilizing selection toward moderate-sized individuals and may explain the absence of size-related effects on fecundity and longevity previously reported for several other lepidopterans. 相似文献
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OBJECTIVE: To describe the experiences of female family physicians who practise obstetrics in balancing professional obligations with personal and family needs, given the unique challenges that such practice poses for these physicians. DESIGN: Qualitative study. SETTING: Ontario. PARTICIPANTS: A purposefully selected sample of nine female family physicians who met the criteria of being married, having children and currently practising obstetrics. OUTCOME MEASURES: Experiences of female family physicians and their strategies in their personal, family and professional lives that enable them to continue practising obstetrics. RESULTS: All participants continued to practise obstetrics because of the pleasure they derived from it, despite the challenges of balancing the unpredictable demands of obstetrics with their personal and family needs. To continue in obstetrics, they needed to make changes in their lives, either through a gradual, evolutionary process or in response to a critical event. Alterations to work and family arrangements permitted them to meet the challenges and led to increased satisfaction. Changes included making supportive call-group arrangements, limiting work hours and the number of births attended and securing help with household duties. CONCLUSIONS: An in-depth examination, through the use of qualitative methods, showed the reasons why some female family physicians continue to practise obstetrics despite the stressful aspects of doing so. This knowledge may be useful for women who are residents or experienced clinicians and who are considering including obstetrics in their practice. 相似文献
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Zebra patterns in fly embryos: activation of stripes or repression of interstripes? 总被引:10,自引:0,他引:10
S B Carroll 《Cell》1990,60(1):9-16
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Vallabh O. Shah Casey Carroll Ryan Mals Donica Ghahate Jeanette Bobelu Phillip Sandy Kathleen Colleran Ronald Schrader Thomas Faber Mark R. Burge 《PloS one》2015,10(5)