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81.
Summary Facultative paedomorphosis in salamanders occurs when larvae respond to varying environmental conditions by either metamorphosing into terrestrial metamorphic adults or retaining their larval morphology to become sexually mature paedomorphic adults. Several hypotheses have been proposed for the evolutionary maintenance of this environmentally induced dimorphism, but few data are available to assess them adequately. We studied a montane population of the tiger salamander,Ambystoma tigrinum nebulosum, and measured the adult growth rate and body condition across three growing seasons to assess the relative costs and benefits of each morph. Metamorphic adults grew more than paedomorphic adults in terms of snout—vent length across years and in weight within years. Dietary analyses and foraging experiments revealed some of the proximate factors that may underlie these differential growth patterns. Across all prey, metamorphs had significantly higher biomass and calories per stomach sample than paedomorphs. Metamorphic diets primarily consisted of the fairy shrimpBranchinecta coloradensis, whereas paedomorphic diets contained a variety of benthic and terrestrial invertebrates. Foraging experiments revealed that both morphs are more successful at capturing fairy shrimp relative to other prey types and both show high electivity toward this prey. However, fairy shrimp occurred only in non-permanent ponds and thus are inaccessible to paedomorphs, which can survive only in permanent ponds. Paedomorphs also experience higher levels of intraspecific competition with large larvae in permanent ponds than metamorphs do in non-permanent ponds. Thus, metamorphs obtain a growth advantage over paedomorphs by foraging in non-permanent ponds that contain fairy shrimp and have reduced intraspecific competition. These results suggest that paedomorphs should have decreased fitness relative to metamorphs, primarily because metamorphs can move into the best habitats for growth. The net fitness effect of morph-specific differences in dispersal depend on whether there are trade-offs with other life history traits. Nonetheless, because the relative benefit of metamorph dispersal will change with environmental conditions in permanent ponds and the surrounding habitat, the relative fitness payoff to each morph should track changes in the environment. Thus, facultative paedomorphosis may be maintained in part by variable, environmentally-specific fitness payoffs to each morph. 相似文献
82.
83.
Hong Luo Benoît Van Coppenolle Marc Seguin Marc Boutry 《Molecular breeding : new strategies in plant improvement》1995,1(1):51-63
Using fourteen random mitochondrial DNA probes, we have examined restriction fragment length polymorphism (RFLP) in wild and cultivatedHevea brasiliensis. A total of 395 accessions, including 345 from various prospectings collected in Brazil, Colombia and Peru and 50 cultivated clones, were analyzed. Two other species (H. benthamiana andH. pauciflora) were also included in the study for comparison. The high level of mitochondrial polymorphism allowed us to divide all the accessions analyzed into 212 distinct genotypes. The genetic variability of cultivated clones was limited to four genotypes forming two clusters. In contrast, considerable genetic variation was found in the wild collections. In almost all cases, accessions displaying the same RFLP profile were restricted to the same geographical area (same or neighbor administrative districts). In addition, accessions whose genetic closeness was predicted by RFLP profiles were also clustered according to geographical origin. In a few cases, however, similar RFLP profiles were found for accessions originating from geographically distant districts. This discrepancy can be explained either by seed dispersion (by river) or possibly by similar genetic events occurring independently in different geographical locations. Chloroplast DNA RFLP was also analyzed in 217 accessions, representative of 126 distinct mitochondrial genotypes. Very few differences were found, indicating that the chloroplast genome is more highly conserved than the mitochondrial genome. 相似文献
84.
二核苷酸重复多态性的非同位素检测及其在基因诊断中的应用 总被引:9,自引:1,他引:8
本文报道了一种检测二核苷酸重复多态性的简便的非同位素法,利用重复序列两侧的特异引物进行PCR扩增,产生的等位片段在薄层变性聚丙烯酰胺凝胶电泳上分离,再用灵敏的银染法显色。该方法不需要标记PCR产物,简便、快速,分辨率可达1bp,并可用多对引物同时进行多重PCR分析。用此方法对DMD家系成员dystrophin基因的5'-脑型外显子止游区和3'-非翻译区的两个(CA)。位点进行了扩增片段长度多态性分 相似文献
85.
家鸡和原鸡的线粒体DNA多态性比较 总被引:17,自引:0,他引:17
本文运用11种限制性内切酶分析了家鸡(茶花鸡、尼西鸡、大理漾濞黄鸡)和原鸡共10只个体的线粒体DNA限制性片段长度多态性(RFLP),平均每个个检测到的片段为40条左右。但仅发现3种变异的限制性片制性格局,即StuI-B,Eca-I-b和RI-B.其中StuI-B和ScaI-B为首次报道,而且均为原鸡所物有,EcoRI-B则为大理漾濞黄鸡所特有。茶花鸡和尼西鸡拥有完全相同的限制性格局。经过计算,原 相似文献
86.
K. Bender R. T. Seibert T. F. Wienker V. Kren M. Pravenec S. Bissbort 《Biochemical genetics》1994,32(5-6):147-154
A genetic locus controlling the electrophoretic mobility of a methylglyoxal dehydrogenase (EC 1.2.1.23) in the rat is described. The locus, designatedMgd1, is expressed in liver and kidney. Inbred rat strains have fixed either alleleMgd1
a
or alleleMgd1
b
. Codominant expression is observed in heterozygotes, providing evidence for a tetrameric enzyme structure. Backcross progenies showed the expected 1:1 segregation ratio, and there is evidence thatMgd1 is linked toPep3 andFh1 on chromosome 13. There is also evidence for two additional methylglyoxal dehydrogenases:Mgd2, present in liver and kidney, andMgd3, present only in heart.Supported by the Deutsche Forschungsgemeinschaft (Grant Be 352/18-1). 相似文献
87.
The cellar population of Drosophila melanogaster at the Chateau Tahbilk Winery (Victoria, Australia) was perturbed for alcohol dehydrogenase (Adh) gene frequencies. Phenol oxidase (Phox) frequencies were also perturbed and monitored as a control. Subsequent gene frequency changes, together with information on population structure, indicated that selection acted on the chromosome regions of both loci. Adh gene frequencies returned to preperturbation levels in a predictable manner. A model in which the relative fitness of Adh phenotypes was determined by temperature-dependent specific activities of enzymes of Adh genotypes adequately accounts for the rate of gene frequency change at this locus. Thus temperature behaves as a selective agent in modulating Adh gene frequencies in this cellar environment. 相似文献
88.
Hitoshi Suzuki Kimiyuki Tsuchiya Mitsuru Sakaizumi Shigeharu Wakana Susumu Sakurai 《Journal of molecular evolution》1994,38(2):107-112
An analysis by restriction endonuclease digestion of ribosomal DNA (rDNA) was carried out in natural populations of Apodemus speciosus, a field mouse that is endemic to Japan. Two restriction sites, the EcoRI (E3) and DraI (D4) sites, in the nontranscribed spacer region downstream from the gene for 28S RNA showed polymorphism within and between individuals in the populations from the Japanese main islands. By contrast, populations from the small adjoining islands which are thought to have separated from the main islands 1–2 × 104 years ago showed relatively low levels of polymorphism within and between individuals, i.e., one of the polymorphic bands in the case of each enzyme was predominant in these populations, irrespective of the variants. These results indicate that the rate of fixation of site variations depends on population size and that the direction of fixation is random. Furthermore, each polymorphic restriction site seems to be fixed independently.Correspondence to: H. Suzuki 相似文献
89.
S. Weining L. Ko R. J. Henry 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1994,89(4):509-513
-Amylases are the key enzymes involved in the hydrolysis of starch in plants. The polymerase chain reaction (PCR) was used to detect polymorphisms in the length of amplified sequences between the annealing sites of two primers derived from published -amy1 gene sequences in barley. These two primers (Bsw1 and Bsw7), flanking the promoter region and the first exon, amplified two PCR fragments in barley. One of the amplified products, with the expected length of 820 bp, appeared together with another shorter PCR band of around 750 bp. This 750-bp fragment seems to be derived from an -amylase gene not reported previously. Both of the PCR products could be amplified from the two-rowed barley varieties tested, including cv Himalaya from which the sequence information was obtained. Five of the six-rowed barley varieties also have the two PCR fragments whereas another two have only the long fragment. These two fragments seem to be unique to barley, neither of them could be amplified from other cereals; for example, wheat, rye or sorghum. These two -amylase fragments were mapped to the long arm of 6H, the location of the -amy1 genes, using wheat-barley addition lines. Amplification of genomic DNA from wild barley accessions with primers Bsw1 and Bsw7 indicated that both of the fragments could be present, or the long and short fragments could be present alone. The results also demonstrated that the genes specifying these two fragments could be independent from each other in barley. The conserved banding pattern of these two fragments in the two-rowed barley varieties implies that artificial selection from these genes may have played an important role in the evolution of cultivated barley from wild barley. 相似文献
90.
D. K. X. Chong C. C. Chinnappa F. C. Yeh S. Chuong 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1994,88(5):614-617
Inheritance of chloroplast DNA (cpDNA) was examined in F1 progenies derived from three crosses and three corresponding reciprocal crosses betweenStellaria porsildii andS. longifolia. Chloroplast DNA restriction fragments were analyzed using methods of nonradioactive digoxigenin-11-dUTP labeling and chemiluminescent detection with Lumi-Phos 530. Distinct interspecific restriction fragment polymorphisms were identified and used to demonstrate the mode of cpDNA inheritance. Mode of cpDNA inheritance differed among crosses. Two crosses in whichS. porsildii, SP2920-21, was the maternal parent exhibited three different types of plastids, maternal, paternal and biparental, among the F1 hybrids, suggesting a biparental cpDNA inheritance and plastid sorting-out inStellaria. 相似文献