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71.
JESSICA LYN WARD DEBORAH ANN MCLENNAN 《Biological journal of the Linnean Society. Linnean Society of London》2009,96(4):769-783
Using geometric morphometric methods, we evaluated the correlation between phenotypic variation and available historical and habitat information for two genetically differentiated, allopatric lineages of a widespread North American species, the brook stickleback ( Culaea inconstans ). The results obtained revealed strong patterns of structured phenotypic differentiation across the species range with extreme phenotypes occurring at the northwest and southeast range boundaries. Shape variation was broadly congruent with the distribution of two mitochondrial DNA lineages; a deep-bodied eastern form (Atlantic refugium) and a slim-bodied western form (Mississippian refugium); however, the two forms were not lineage-specific and phenotypic cladistic diversification is likely to be an artefact of underlying clinal variation associated with longitudinal and latitudinal gradients. In addition, we found little evidence of diagnosable lake and river forms across North America. Taken together, large-scale patterns of phenotypic diversity observed in C. inconstans suggest that relatively recent factors, such as continually varying natural selection across the range and/or potential local gene flow, may substantially mitigate the effects of historical separation or a generalized adaptive response to alternative habitats. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 769–783. 相似文献
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THOMMES ROBERT C.; HYLKA VINCENT W.; TONETTA SHARNO A.; GRIESBACH DEBORAH A; ROPKA STACIE L.; WOODS JAMES E. 《Integrative and comparative biology》1988,28(2):417-426
SYNOPSIS. In the chick embryo, the period of 10.0 to 13.0 daysof incubation is critical in the maturation of the hypothalamic/adenohypophysealor adenohypophyseal regulation of thyroid function; the establishmentof thyroid regulation at this time is reflected in a markedincrease in thyroid function. There has been general agreementthat the "feed-forward" and the "feed-backward" loops of theadenohypophyseal-thyroid unit are established on or about day11.5, but whether these events were the result of the establishmentof pituitary-thyroid interactions alone or included hypothalamicregulation of the pituitary-thyroid unit has until quite recentlyremained problematical. Data presented in the present reviewindicate that beginning on or about day 11.5 the hypothalamuscan and does regulate the pituitary-thyroid unit. Although thehypothalamus is essential for the maintenance of normal pituitary-thyroidfunction, the data strongly suggest that the immediate eventwhich is responsible for the establishment of a functional hypothalamoadenohypophyseal-thyroid axis in the developing chick embryo is a marked increasein adenohypophyseal thyrotrophs on day 11.5. 相似文献
74.
JAMES A. DVORAK DEBORAH L. HARTMAN MICHAEL A. MILES‡ 《The Journal of eukaryotic microbiology》1980,27(4):472-474
SYNOPSIS. Trypanosoma ( Schizotrypanum ) cruzi clones were derived from isolates of an acute human case of Chagas' disease (strain Esmereldo), a human case of T. cruzi infection (strain CAN-III) and from a naturally infected opossum (strain WA-250). The isoenzyme patterns and growth rates of the clones were stable during long-term cultivation, by serial passages, of the parasites in liquid medium. Both clones of strain Esmereldo were zymodeme II; the 2 clones of strain CAN-III, zymodeme III; and the 5 clones of strain WA-250, zymodeme I. The range in doubling times of the parasite populations in liquid medium were 36–49. 7 h (strain WA-250), 117.2–133.7 h (Esmereldo clones) and 169–208 h (CAN-III clones). 相似文献
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Variation in rates of nitrogen fixation in termites: response to dietary nitrogen in the field and laboratory 总被引:2,自引:0,他引:2
Abstract. Termites contribute nitrogen to their habitat through the nitrogenase activity of their bacterial symbionts. Previous studies indicate that high levels of dietary nitrogen suppress nitrogen fixation in termites. We examined the effects of dietary nitrogen on fixation rates in termites in both field and laboratory experiments. Ten field cplonies of Reticulitermes were collected and assayed for nitrogenase activity in July 1993, October 1993, January 1994, and April 1994. The nitrogen content of the wood collected with each colony was determined. There was no correlation between termite nitrogen fixation rates and the amount of nitrogen in their food for any of the four collection periods. In laboratory experiments, nitrogen fixation rates decreased when termites were fed filter paper treated with 2% and 5% ammonium nitrate or a 5% mixture of the amino acids proline, tryptophan and leucine, compared to water-treated controls. By contrast, the nitrogenase activity of termites fed filter paper treated with 2% and 5% ammonium phosphate, a mixture of the amino acids histidine, serine and aspartic acid, or 2% and 5% urea did not differ from the controls. However, nitrogenase activity increased when termites were fed with 2% uric acid. No clear association exists between termite nitrogen fixation and the nitrogen content of their food. 相似文献
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DEBORAH KAPCHAN 《American anthropologist》2007,109(2):381-382
Berber Culture on the World Stage: From Village to Video . Jane E. Goodman. Bloomington: Indiana University Press, 2005. 239 pp. 相似文献
78.
DEBORAH I. OLSZEWSKI 《American anthropologist》2007,109(2):390-392
Behavioral Ecology and the Transition to Agriculture . Douglas J. Kennett and Bruce Winterhalder, eds. Berkeley: University of California Press, 2006. 394 pp. 相似文献
79.
Stable isotopes, mesocosms and gut content analysis demonstrate trophic differences in two invasive decapod crustacea 总被引:3,自引:0,他引:3
1. Improving our understanding of dietary differences among omnivorous, benthic crustacea can help to define the scope of their trophic influence in benthic food webs. In this study, we examined the trophic ecology of two non‐native decapod crustaceans, the Chinese mitten crab (Eriocheir sinensis) (CMC) and the red swamp crayfish (Procambarus clarkii) (RSC), in the San Francisco Bay ecosystem to describe their food web impacts and explore whether these species are functionally equivalent in their impacts on aquatic benthic communities. 2. We used multiple methods to maximise resolution of the diet of these species, including N and C stable isotope analysis of field data, controlled feeding experiments to estimate isotopic fractionation, mesocosm experiments, and gut content analysis (GCA). 3. In experimental enclosures, both CMC and RSC caused significant declines in terrestrially derived plant detritus (P < 0.01) and algae (P < 0.02) relative to controls, and declines in densities of the caddisfly Gumaga nigricula by >50% relative to controls. 4. Plant material dominated gut contents of both species, but several sediment‐dwelling invertebrate taxa were also found. GCA and mesocosm results indicate that CMC feed predominantly on surface‐dwelling invertebrates, suggesting that trophic impacts of this species could include a shift in invertebrate community composition towards sediment‐dwelling taxa. 5. Stable isotope analysis supported a stronger relationship between CMC and both algae and algal‐associated invertebrates than with allochthonous plant materials, while RSC was more closely aligned with terrestrially derived detritus. 6. The trophic ecology and life histories of these two invasive species translate into important differences in potential impacts on aquatic food webs. Our results suggest that the CMC differs from the RSC in exerting new pressures on autochthonous food sources and shallow‐dwelling invertebrates. The crab's wide‐ranging foraging techniques, use of intertidal habitat, and migration out of freshwater at sexual maturity increases the distribution of the impacts of this important invasive species. 相似文献
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