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Seasonal changes in the mean size of tsetse, Glossina pallidipes Austen, as indicated by wing vein length, were monitored during 1983-86 at Nguruman, southwestern Kenya. Changes in size of nulliparous females and wing fray category 1 males were shown to be correlated with the relative humidity 2 months before they were captured. Soil temperature when flies were in the pupal stage had much less effect. Size dependent mortality was demonstrated, with the mean size of flies emerging from pupae significantly less than that of field-caught flies. This mortality must occur at emergence, since there was no evidence of size-dependent mortality once the flies became available to the trap. Size was correlated with density-independent mortality acting on the parent population 2 months previously. It might therefore be possible to use size as an index of the intensity of such mortality. This could be useful when assessing the level of additional mortality required to suppress tsetse populations.  相似文献   
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Nuclear DNA sequences from late Pleistocene megafauna   总被引:6,自引:1,他引:5  
We report the retrieval and characterization of multi- and single-copy nuclear DNA sequences from Alaskan and Siberian mammoths (Mammuthus primigenius). In addition, a nuclear copy of a mitochondrial gene was recovered. Furthermore, a 13,000-year-old ground sloth and a 33,000- year-old cave bear yielded multicopy nuclear DNA sequences. Thus, multicopy and single-copy genes can be analyzed from Pleistocene faunal remains. The results also show that under some circumstances, nucleotide sequence differences between alleles found within one individual can be distinguished from DNA sequence variation caused by postmortem DNA damage. The nuclear sequences retrieved from the mammoths suggest that mammoths were more similar to Asian elephants than to African elephants.   相似文献   
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Conclusion Packard attempted to incorporate cave fauna into a general theory of evolution that would be consistent with the principle of recapitulation, and would have as the primary mechanism the inheritance of the effects of the environment. Beyond this, he also attempted to demonstrate that the evolution of cave fauna was consistent with progressive evolution. The use he made of comparative anatomy and embryology places him within the tradition of classical morphology that was dominant through much of the last half of the nineteenth century, but of waning importance by the time of Packard's death in 1905. The importance Packard gave to cave fauna as evidence for Lamarckian evolution stimulated interest in the phenomenon; this interest, and references to cave fauna in the scientific literature, declined after his death. Since then, the importance of cave fauna in evolutionary theory has declined from their status as the star evidence in Packard's theory to their present status as a difficult anomaly within the modern synthetic theory.  相似文献   
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