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Fred Cooke C. Scott Findlay Robert F. Rockwell Judith A. Smith 《Evolution; international journal of organic evolution》1985,39(1):165-177
Between 1969 and 1977 the frequency of the blue phenotype of the dimorphic Lesser Snow Goose (Anser caerulescens caerulescens) showed a steady increase at the La Pérouse Bay colony near Churchill, Manitoba. Cooch (1961, 1963) suggested the global increase resulted from selection pressures favoring blue individuals. The selection hypothesis was evaluated by examining phenotypic differences in net fecundity. We partitioned the reproductive cycle into a series of stages, each defined by a particular index of fecundity. Despite large samples we were unable to detect any significant differences between the two maternal phenotypes in those indices that could conceivably influence population dynamics. We cannot, however, dismiss selection as the mechanism of population change, nor as a contributor to the maintenance of the polymorphism without assessing potential phenotypic differences in viability, age of maturation, and breeding propensity. These attributes are examined in the following paper (Rockwell et al., 1985). 相似文献
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C. Scott Findlay R. F. Rockwell Judith A. Smith Fred Cooke 《Evolution; international journal of organic evolution》1985,39(4):904-914
The investigated the hypothesis that positive assortative mating for plumage coloration observed in populations of the dichromatic Lesser Snow Goose (Anser caerulescens caerulescens) evolved and persists due to selective advantages accruing to individuals choosing mates phenotypically similar to themselves. We examined potential differences between pure (white × white, blue × blue) and mixed (white × blue, blue × white) pairs for an array of fitness components related to both fecundity and viability. While no differences were detected for most components, mixed pairs consistently enjoyed enhanced nesting success relative to their pure counterparts. In addition, pre-reproductive viability and female offspring recruitment were significantly greater for mixed pairs for some of the cohorts examined. Not only have we failed to find enhanced reproductive success associated with positive assortment, we have provided evidence that there is some advantage associated with negative assortment. In light of our findings, we suggest: 1) that positive assortment results from the use of familial color as one element in species recognition; 2) that the enhanced fitness of mixed pairs, particularly with respect to nesting success, results from complementation of parental behavior; and 3) that while negative assortment will not likely become the rule in this population, the selective advantage of mixed pairs is a potential determinant of pair type frequencies in the La Pérouse Bay population. 相似文献
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Robert F. Rockwell C. Scott Findlay Fred Cooke Judith A. Smith 《Evolution; international journal of organic evolution》1985,39(1):178-189
Cooch (1961, 1963) suggested that changes in the genotypic composition of snow goose colonies comprising the Hudson Bay-Foxe Basin population could be attributed to selection favoring the blue phenotype. In the preceding paper (Cooke et al., 1985), we examined potential differences in net fecundity between the two phenotypes at La Pérouse Bay in northern Manitoba. No substantial differences in any component of fecundity were detected. In the present paper, we examined potential differences in pre-reproductive and adult viability, age of maturation, and breeding propensity. Again, no differences associated with the plumage polymorphism were detected in any of these life history characteristics. Thus, despite a thorough analysis of the complete life cycle, we were unable to uncover any evidence supporting a selection hypothesis for the persistence and dynamics of this conspicuous polymorphism. An alternate hypothesis based primarily on gene flow and assortative mating appears more plausible. 相似文献
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P. J. K. BURTON 《Ibis》1978,120(2):171-177
The Harrier-Hawks Polyboroides spp. and Crane Hawk Geranospiza caerulescens have legs capable of flexing backward as well as forward at the intertarsal joint. This is evidently adaptive to their habit of extracting prey from crevices using the feet. The structure and properties of the intertarsal joint have been investigated using an alcoholic specimen of P. typus and skeletons of P. typus and G. caerulescens; specimens of Circus cayaneus (alcoholic) and C. aeruginosus (skeleton) were used for comparison. Increased mobility of the joint extends to medial-lateral swing as well as flexion; the faculty for backward flexion appears to be somewhat offset by some loss of forward flexion. The tibiotarsus, tarsometatarsus and the ligaments and menisci of the intertarsal joint are described and figured. No significant differences in musculature were found. The most obvious difference between Circus on the one hand, and Polyboroides and Geranospiza on the other is the extreme narrowness of the joint in the latter two genera. This is probably the most important factor permitting increased joint mobility. The possible significance of other structural features observed is also discussed, and related adaptations of the distal tarsometatarsus and foot are pointed out. It is concluded that the resemblances of the hind limbs of these two genera are not strong evidence of phylogenetic relationship. 相似文献
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Leaves of Quercus velutina Lam. parasitized by Taphrina caerulescens (Desm.) Tulanse were examined with the electron microscope to ascertain cellular aberrations that were induced by the fungus. Major changes were most apparent in the lower epidermis, where cellular divisions and enlargement were common, the cell walls becoming irregularly thickened. Many of the ultrastructural features of the diseased cells resembled those of meristematic cells; the absence of a large central vacuole, a disproportionately large nucleus, and an abundance of cytoplasmic organelles. Chloroplasts with large amounts of starch were also routinely observed. 相似文献
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THLASPI CAERULESCENS J. & C. PRESL. (T. ALPESTRE L.) IN BRITAIN 总被引:1,自引:1,他引:0
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沙门菌CWDMs脂代谢检测 总被引:9,自引:2,他引:7
采用毛地黄皂苷敏感试验和菌细胞胆固醇、甘油三脂及胆碱酯酶定性与定量分析法,检测伤寒杆菌和甲型副伤寒杆菌经L 型变异后形成的细胞壁缺陷突变株(CW DM )的脂类代谢活性,了解这些CW DM 变异的性质和探讨细菌细胞壁缺陷突变与细菌演变的关系。结果表明,沙门菌CW DM s 具有显著的胆固醇和甘油三脂代谢活性、对毛地黄皂苷高度敏感并且还具有与白色念珠菌相似的胆固醇和甘油三脂的含量,但未能检出胆碱酯酶活性。CW DM s返祖菌丧失了脂类代谢酶类和胞浆膜不含胆固醇,恢复了与其亲代细菌型相似的代谢特征。提示在沙门菌天然即存在有与脂类及胆固醇代谢相关的基因,细胞壁的缺陷导致这些脂类及胆固醇代谢基因活化,以致 CW DM s 能够表达固醇和甘油三脂代谢活性和胞浆膜含有胆固醇 相似文献
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沙门菌CWDMs氨基酸代谢的检测 总被引:3,自引:0,他引:3
采用氨基氨利用生长试验和谷丙转氨酶(GPT)、谷草转酶(GOT)、乳酸脱氨酶(LDH)、肌酸激酶(CK)、α-闳丁酸脱氢酶(α-HBD)、γ-谷志肽酶(γ-GT),酸性磷酸酶(ACP)定性与定量分析法,检测伤CWDMs变异的特点及其机制,探讨CWDMs变异的性质及其与细胞壁缺陷突变的关系。结果表明,沙门菌CWDMs变异的性质及其与细胞壁缺陷突变的关系。结果表明,沙门菌CWDMs在仅含蛋氨酸或脯氨 相似文献
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采用聚丙烯酰胺凝胶电泳法检测伤寒杆菌和甲型副伤寒杆菌的CWDMs及其宁代细菌型和伤寒杆菌粗糙型的乳酸脱氢酶(LDH)同功酶,以了解沙门菌CWDMs生物氧化的特点和机制,探讨CWDMs变异的性质。结果表明,伤寒杆菌和甲型副伤寒杆菌的细菌型及伤寒杆粗糙型在聚丙烯酰胺凝胶电泳后显示出相同的4种具有不同泳动速率的LDH同功酶,但CWDMs仅显示2种LDH。CWDMs的2种LDH同功酶与其亲代细菌型及伤寒杆 相似文献
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光照对蕨类植物配子体假根向重力性的影响 总被引:3,自引:0,他引:3
对8种蕨类植物配子体假根向重力性反应的研究结果表明,除卷柏Selaginella tamariscina Spring配子体假根无向重力性反应并且其生长方向与光照方向无关外,其它7种的配子体假根均有向重力性反应,并且假根的向重力性反应在配子体发育初期,因光照的方向不同而异,表现为负向光性。随着配子体发育至片状体阶段,光对其向重力性反应的影响逐渐减弱,而重力的影响增强。在蕨类植物配子体发育初期,光对 相似文献
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