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ANDREA VAUPEL KATRIN KLINGE MARTIN BRÄNDLE VOLKER WISSEMANN TEJA TSCHARNTKE ROLAND BRANDL 《Biological journal of the Linnean Society. Linnean Society of London》2007,90(4):619-625
We tested for genetic differentiation between populations of Rhagoletis alternata Fall. (Diptera: Tephritidae) on three different host species. We collected larvae from three rose species of the section Caninae ( Rosa canina L., Rosa corymbifera Borkh . , and Rosa rubiginosa L.) from 15 sites across Germany, where the three roses occurred together. Additionally, we sampled three sites in Switzerland. Roses differ in morphology (e.g. leaf glands) as well as phenology. We were able to score nine allozyme loci (five polymorphic). Populations from the three hosts did not differ in genetic variability. We found significant genetic differentiation between populations from different host species. However, the differentiation was very low (0.9%). Hence, we found no indication for host races. Furthermore, surprisingly little geographical structure of genetic differentiation was found between populations of this fruit fly across central Europe. We offer three mutually non-exclusive explanations for these findings. First, gene flow between populations of Rh. alternata is high. Second, the pattern of genetic differentiation is based on a recent expansion of the distributional range . Third, the ongoing gene flow between roses of the section Caninae acts as a hybrid bridge. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 90 , 619–625. 相似文献
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Birds on migration spend much more time on stopover sites to refuel for the next migration step than aloft, but empirical data on stopover duration are rare, especially for Palearctic trans-Sahara migrants whilst crossing the desert. Previous studies suggest that stopover duration of fat birds in oases is much shorter than that of lean birds. During 2003 and 2004 capture–recapture data of migrating passerines from two inland oases in spring and from one coastal site in autumn in Mauritania, West Africa, were analysed to test whether the probability of being a transient and the stopover duration depend on fuel stores at first capture. The application of capture–recapture models revealed that during autumn migration at the coast the proportion of transients (individuals that stop over only for 1 day) was relatively high (77–90%) in three out of four species investigated and stopover duration was short (1.9–4.6 days). In the inland oases in spring, transients were detected in only four out of 12 analyses. Stopover duration was longer than at the coast in autumn and surprisingly long in some species with durations of up to 30 days. Models taking into account the initial fat load of birds on the first capture occasion were, with one exception, never the most parsimonious ones. This indicates that the time spent after and before capture at the stopover site did not depend on the fat stores at first capture. Therefore, we cannot confirm the assumption that birds arriving at stopover sites in the desert with low fat loads stay longer than birds that arrive with high fat loads. 相似文献
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We assessed the potential of using 14C contents of soil respired CO2 to calculate the contributions of heterotrophic and autotrophic respiration to total soil respiration. The partitioning of these fluxes is of utmost importance to evaluate implications of environmental change on soil carbon cycling and sequestration. At three girdled forest stands in Sweden and Germany, where the tree root (autotrophic) respiration had been eliminated, we measured both flux rates and 14C contents of soil respired CO2 in girdled and control plots in the summers of 2001 or 2002. At all stands, CO2 flux rates were slightly higher in the control plots, whereas the 14C contents of respired CO2 tended to be higher in the girdled plots. This was expected and confirmed that heterotrophically respired CO2 cycles more slowly through the forest ecosystem than autotrophically respired CO2. On the basis of these data, the contributions of hetero‐ and autotrophic respiration to total soil respiration were calculated using two separate approaches (i.e. based on flux rates or 14C). Fractions of heterotrophic respiration ranged from 53% to 87%. Values calculated by both approaches did not differ significantly from each other. Finally, we compared the 14C contents of soil respired CO2 in the girdled plots with the 14C contents of heterotrophically respired CO2 calculated by three different 14C models. None of the models matched the measured data sufficiently. In addition, we suspect that inherent effects of girdling may cause the 14C content of CO2 respired in the girdled plots to be lower than ‘true’ heterotrophically respired CO2 in an undisturbed plot. Nevertheless, we argue that measurements and modeling of 14C can be developed into a valuable tool for separating heterotrophic and autotrophic soil respiration (e.g. when girdling cannot be performed). 相似文献