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901.
Stephanie A. Blain Dolph Schluter Colin E. Adams Per-Arne Amundsen Rune Knudsen Louise Chavarie 《Global Ecology and Biogeography》2023,32(12):2257-2270
Aim
High repeatability among assemblages of closely related but ecologically distinct ecotypes implies predictability in evolution and assembly of communities. The conditions under which ecotype assemblages form predictably, and the reasons, have been little investigated. Here, we test whether repeatability declines as the number of ecotypes builds.Location
Postglacial lakes with a circumboreal distribution.Time Period
Data were extracted from studies published between 1982 and 2019.Major Taxa Studied
Ecotype assemblages from two Salmonid genera – Salvelinus and Coregonus. Fish in postglacial lakes commonly occur as pairs of ecotypes, typically with a pelagic and a littoral/benthic form, but in Salvelinus and Coregonus, assemblages commonly contain multiple sympatric ecotypes.Methods
We used a meta-analysis of Salvelinus and Coregonus to empirically assess how repeatability varies across assemblages of two to seven ecotypes. We examined repeatability of use of broad niche categories as well as underlying phenotypic traits.Results
Within Coregonus, repeatability across multi-ecotype assemblages did not break down with the addition of a third or fourth ecotype. However, in Salvelinus, repeatability was largely absent and independent of the number of ecotypes. Repeatability of trait frequency distributions was absent in both genera, yet associations between trait means and niche categories were evident, especially in Coregonus.Main Conclusions
These results show that repeatability can vary greatly between lineages; that repeatability need not break down as the number of ecotypes builds; and that high repeatability of broad niche categories may result despite marked differences in the underlying frequency distribution of trait means. These findings not only affirm the presence of repeatable ecotype assembly and early stages of divergence in postglacial fishes at a global scale, but also highlight variability among taxa and underlying phenotypic traits. 相似文献902.
903.
904.
M. N. Obeyesekere E. S. Knudsen J. Y. J. Wang & S. O. Zimmerman 《Cell proliferation》1997,30(3):171-194
A mathematical model integrating the roles of cyclin D, cdk4, cyclin E, cdk2, E2F and RB in control of the G1 phase of the cell cycle is described. Experimental results described with murine embryo fibroblasts (MEFs), either Rb+/+ or Rb−/−, and with the RB-deficient osteosarcoma cell line, Saos-2, served as the basis for the formulation of this mathematical model. A model employing the known interactions of these six proteins does not reproduce the experimental observations described in the MEFs. The appropriate modelling of G1 requires the inclusion of a sensing mechanism which adjusts the activity of cyclin E/cdk2 in response to both RB concentration and growth factors. Incorporation of this sensing mechanism into the model allows it to reproduce most of the experimental results observed in Saos-2 cells, Rb−/− MEFS, and Rb+/+ MEFs. The model also makes specific predictions which have not been tested experimentally. 相似文献
905.
906.
The nitrogen response of a barley C-hordein promoter is controlled by positive and negative regulation of the GCN4 and endosperm box 总被引:22,自引:2,他引:20
The 431 bp C-hordein promoter of λ- 1 - 17 exhibits a specific response to amino acids and NH4 NO3 in developing barley ( Hordeum vulgare L.) endosperms. With the aid of particle bombardment it is shown that the GCN4 motif ATGA(C/G)TCAT is the dominating cis -acting element in this response. But synergistic interaction with the neighbouring endosperm motif TGTAAAGT within the bifactorial prolamin element and cooperation with upstream sequences including a second prolamin-like element is an absolute requirement for a strong, positive regulation by an optimal nitrogen regime. Low nitrogen levels convert the GCN4 box into a negative motif. In contrast the endosperm box on its own exerted a silencing activity, independent of nitrogen nutrition. Sequence comparisons revealed that GCN4- and endosperm-like motifs are widely distributed among plant promoters. Their putative role in nitrogen regulation is discussed. 相似文献
907.
Cell adhesion molecules in myogenesis 总被引:7,自引:0,他引:7
K A Knudsen 《Current opinion in cell biology》1990,2(5):902-906