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应用随机扩增多态性DNA（RAPD）技术及细胞色素b（Cytｂ）基因序列,分析了长江口及其南部邻近地区大弹涂鱼（Boleophthalmus pecinirostris）群体遗传结构及种群历史,结果显示这一区域大弹涂鱼群体的遗传多样性水平很高。（1）RAPD分析结果：从100个10碱基随机引物中筛选出30个多态性引物,对长江口九段沙湿地、浙江舟山定海、福建霞浦群体各20个体进行RAPD分析,3个群体分别获得236、270、274条带,共301个有效位点。3群体多态位点比例（P）、Nei基因多样性指数（H）、Shannon多样性指数（I）分别在93.02%—96.35%、0.3890—0.4219、0.5618—0.6044。分子方差分析（AMOVA）表明,大弹涂鱼群体间存在显著的遗传分化（Fst= 0.03004-0.03254,P<0.05）,但仅3.2%的遗传变异来自群体间。（2）Cytｂ基因序列分析结果：从采自九段沙、定海、霞浦及浙江慈溪的42尾大弹涂鱼样本中,共获得33个Cytｂ基因单倍型（序列长1 141 bp）。4群体的平均单倍型多样性（h）、核甘酸多样性（π）分别为0.9814、0.0048。4群体间的遗传分化指数Fst为0.00043—0.07814,仅1.93%的变异来自群体间（AMOVA分析）,而基因交流值却达14.50—30.79,群体间K2-P遗传距离为0.0040—0.0056,从而显示大弹涂鱼群体间没有发生明显的地理分化。以Cyt b基因序列构建的NJ树揭示4个群体的个体组成2个谱系,但这2个谱系与地理分布并不相关。中性检验、错配分析和网络亲缘关系分析皆表明大弹涂鱼群体有过种群扩张,扩张时间约在更新世末期的0.057—0.023百万年前。 相似文献
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四川大头茶种群生殖生态学研究：I.生殖年龄,生殖年龄结构及其影响… 总被引：6，自引：0，他引：6
系统地研究了缙云山大头茶种群的生殖年龄、生殖年龄结构及其影响因子。研究结果表明：大头茶种群的Ａｒｍｉｎ、Ａｒｍａｘ、Ａ↑－ｒ和Ａｐｃ值分别为１０ａ、８８ａ、３４ａ和７８ａ,但随群落结构复杂性程度的增加其生殖年龄逐渐递增。缙云山大头茶种群的生殖年龄结构和兴文地区的相似,均为增长型,但前者生殖年龄结构较后者复杂,且前者之生殖年龄结构在不同生境（甚至同一群落的不同海拔样地）中呈现不同类型。影响大头茶种群 相似文献
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研究了我国4个地区3种生活史类型的烟蚜在烟草上的种群繁殖特征,并用Weibull模型对种群存活特征和生殖特征进行了分析。结果表明:25±1℃、14L:10D、70%±10%RH条件下,长春地区烟蚜的生殖前期和产仔高峰日分别为大于等于7d和第11d,而南京、湖南郴州和河南宜阳烟蚜的生殖前期和产仔高峰日分别为小于7d和第9d。烟蚜种群的R0、T和rm在同一地区不同体色之间以及不同地区同一体色之间均存在有差异显著性,平均寿命仅在不同地区的红色烟蚜和褐色烟蚜中有显著性差异,在黄绿色之间差异均不显著。 相似文献
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于光镜下对大弹涂鱼性腺切片作了组织学观察,对大弹涂鱼卵细胞和精子发育规律进行研究。结果表明:大弹涂鱼在一个生殖季节中只能产卵1次,大弹涂鱼属于一次性产卵类型。大弹涂鱼3月卵母细胞进入大生长期发育阶段,4—6月为繁殖盛期,7—8月为繁殖末期。10月卵巢基本修整完毕,进入Ⅱ′恢复期。卵细胞发育可分为6个时相:卵原细胞、卵母细胞单层滤泡、卵母细胞出现脂滴和卵黄、卵母细胞卵黄充满、卵母细胞核极化、卵母细胞退化时相。卵母细胞膜单层,由具有辐射纹的放射带构成,滤泡膜细胞分泌而成的次级卵膜成为成熟卵子的附着丝。大弹涂鱼2月精巢开始发育,5月GSI值达最高值,平均成熟系数达0.70%,排精量最旺盛,出现高峰。7—9月GSI值明显下降。11月至翌年2月GSI值波动于0.08%—0.20%之间,变辐小,此期间精巢处于静止发育状态。大弹涂鱼的精巢属于小叶型结构。精子发育分为6个时期:精原细胞期、精原细胞增殖期、精母细胞生长成熟期、精子细胞变态期、精子成熟期和退化吸收期。繁殖季节精小叶内充满精子,精小囊消失。 相似文献
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探讨大苞山茶(Camelliagranthamiana)的野外种群结构,揭示大苞山茶种群的更新过程及发展趋势,可为其保护及可持续利用提供科学依据。该研究以广东省紫金县内的两个大苞山茶种群作为研究对象,通过编制静态生命表,计算数量动态指数,绘制存活曲线和种群生存力函数曲线,并采用种群数量时间序列预测的方法对大苞山茶种群的结构和动态特征进行分析。主要结果如下:1)两个大苞山茶的种群均为幼龄个体占比高的金字塔型结构,鹿子嶂种群和杨梅坝种群的幼龄个体(Ⅰ、Ⅱ龄级)分别占总数的71.48%、64.32%,但幼苗死亡率高;2)两个种群的存活曲线均趋近于Deevey-Ⅱ型,说明大苞山茶各龄级死亡率基本相同;3)两个种群在忽略外部干扰时的数量动态指数(Vpi)和考虑外部干扰时的数量动态指数(V′pi)均大于0,而V′pi趋近于0,属于不稳定的增长型种群,其中,杨梅坝种群的稳定性相对较好;4)生存函数分析表明,两个种群的生存率和累计死亡率在Ⅰ、Ⅱ龄级达到了平衡, Ⅴ龄级后生存曲线变化幅度变小,有限的个体开始进入生理衰退期; 5)时间序列预测的结果为:在经历未来2、4、6、8龄级后,每个龄级的个体数量均有... 相似文献
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植物种群营养生长和生殖生长的关系是植物生殖生态学研究的重要内容之一,自本世纪７０年代,国外已有大量报道,但国内的研究报道很少。本在种群水平上研究了人工油松种群一年生雌性枝条和雄性枝条在枝长、直径、叶数、叶生物量、枝生物量及新生枝条在大小孢子球生物量、雌雄枝条长度和生物量等方面的差异,结果表明,一年生枝条除在西方向上雌雄枝条直径差异显和在东、西方向上雌雄枝条生物量差异显外,其它处理条件下雌雄枝 相似文献
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羊草种群能量生殖分配的研究 总被引：18，自引：4，他引：18
对羊草种群能量生殖分配规律研究表明,在羊草种群中,各构件热值的大小顺序为穗〉营养枝叶鞘〉生殖枝叶鞘〉营养枝叶〉营养枝茎〉生殖枝茎〉生殖枝叶〉凋落物;营养生长和生殖生长的能量分配比例的大小顺序为营养枝〉根茎〉凋落物〉生殖枝;各构件能量分配比例的季节动态也有差异,在羊草种群的生殖枝构件中,茎和叶鞘的分配比例较大,而穗和叶的能量分配比例较小。 相似文献
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Markow TA Castrezana S Pfeiler E 《Evolution; international journal of organic evolution》2002,56(3):546-552
Between sister species of Drosophila, both pre- and postzygotic reproductive isolation commonly appear by the time a Nei's genetic distance of 0.5 is observed. The degree of genetic differentiation present when allopatric populations of the same Drosophila species exhibit incipient reproductive isolation has not been systematically investigated. Here we compare the relationship between genetic differentiation and pre- and postzygotic isolation among allopatric populations of three cactophilic desert Drosophila: D. mettleri, D. nigrospiracula, and D. mojavensis. The range of all three is interrupted by the Gulf of California, while two species, D. mettleri and D. mojavensis, have additional allopatric populations residing on distant Santa Catalina Island, off the coast of southern California. Significant population structure exists within all three species, but only for allopatric populations of D. mojavensis is significant isolation at the prezygotic level observed. The genetic distances for the relevant populations of D. mojavensis were in the range of 0.12, similar to that for D. mettleri whose greatest D = 0.11 was unassociated with any form of isolation. These observations suggest further investigations of Drosophila populations with genetic distances in this range be undertaken to identify any potential patterns in the relationship between degree of genetic differentiation and the appearance of pre- and/or postzygotic isolation. 相似文献
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In sexual reproduction the genetic similarity or dissimilarity between mates strongly affects offspring fitness. When mating partners are too closely related, increased homozygosity generally causes inbreeding depression, whereas crossing between too distantly related individuals may disrupt local adaptations or coadaptations within the genome and result in outbreeding depression. The optimal degree of inbreeding or outbreeding depends on population structure. A long history of inbreeding is expected to reduce inbreeding depression due to purging of deleterious alleles, and to promote outbreeding depression because of increased genetic variation between lineages. Ambrosia beetles (Xyleborini) are bark beetles with haplodiploid sex determination, strong local mate competition due to regular sibling mating within the natal chamber, and heavily biased sex ratios. We experimentally mated females of Xylosandrus germanus to brothers and unrelated males and measured offspring fitness. Inbred matings did not produce offspring with reduced fitness in any of the examined life-history traits. In contrast, outcrossed offspring suffered from reduced hatching rates. Reduction in inbreeding depression is usually attributed to purging of deleterious alleles, and the absence of inbreeding depression in X. germanus may represent the highest degree of purging of all examined species so far. Outbreeding depression within the same population has previously only been reported from plants. The causes and consequences of our findings are discussed with respect to mating strategies, sex ratios, and speciation in this unusual system. 相似文献
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Joel R. Peck David Waxman 《Evolution; international journal of organic evolution》1997,51(4):1036-1043
Simple evolutionary models typically assume a homogeneous environment in which all individuals have equal access to resources. However, when dispersal is limited this assumption is unlikely to correspond to reality. Instead, the offspring of relatively fecund parents can be expected to find that resources are scarce because of competition from their relatively large number of siblings. We show that these factors lead to selection for decreased variation in the number of offspring produced. We investigate the relationship between fitness and variation in fertility for a variety of different circumstances. Our results indicate that, in some cases, selection for reduced variation in fertility can be very substantial. 相似文献
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Cyrus Rumisha; 《African Journal of Ecology》2024,62(2):e13259
In the past 24 years, the Southwestern Indian Ocean (SWIO) region has lost about 4% of its mangroves due to unsustainable extraction, land clearance for agriculture and climate change impacts. Since this loss risks fragmenting mangrove fauna, this study analysed 179 D-loop sequences (329 base pairs) of Barred mudskipper (Periophthalmus argentilineatus) sampled from estuarine mangroves in the SWIO to test two hypotheses: (1) whether Barred mudskipper populations in the region display genetic connectivity along the fragmented mangroves and (2) whether these populations have experienced demographic declines in recent history. The populations showed low and insignificant indices of genetic differentiation (FST = −0.00068, p > 0.05; ΦST = 0.005, p > 0.05), and haplotypes from different localities did not cluster according to their geographical origins. Similarly, Bayesian phylogenetic analysis grouped all SWIO haplotypes into one cluster, suggesting the hypothesis of genetic interconnectedness could not be rejected. Furthermore, the populations showed high haplotype diversity (0.96 ± 0.007) combined with low nucleotide diversity (1.09 ± 0.61%). They also showed significant negative Tajima's D values (−1.71, p < 0.02) and a unimodal mismatch distribution, indicating the hypothesis of demographic expansion post a historical bottleneck could not be rejected. Nevertheless, the Bayesian skyline plot indicated an increase in population size post-bottleneck, suggesting an ongoing recovery. These findings indicate that, despite varying management approaches in the SWIO, Barred mudskipper populations exhibit genetic exchange that transcends geographical and administrative borders. This implies that their populations should be considered a single stock within the region. These findings underscore the need for coordinated management approaches among the SWIO countries. This is crucial because inconsistencies in conservation measures across borders could disrupt the population's interconnectedness, potentially impacting their genetic integrity and long-term survival. 相似文献
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V. Vaughan Symonds Pamela S. Soltis Douglas E. Soltis 《Evolution; international journal of organic evolution》2010,64(7):1984-2003
Polyploidy is a major feature of angiosperm evolution and diversification. Most polyploid species have formed multiple times, yet we know little about the genetic consequences of recurrent formations. Among the clearest examples of recurrent polyploidy are Tragopogon mirus and T. miscellus (Asteraceae), each of which has formed repeatedly in the last ～80 years from known diploid progenitors in western North America. Here, we apply progenitor‐specific microsatellite markers to examine the genetic contributions to each tetraploid species and to assess gene flow among populations of independent formation. These data provide fine‐scale resolution of independent origins for both polyploid species. Importantly, multiple origins have resulted in considerable genetic variation within both polyploid species; however, the patterns of variation detected in the polyploids contrast with those observed in extant populations of the diploid progenitors. The genotypes detected in the two polyploid species appear to represent a snapshot of historical population structure in the diploid progenitors, rather than modern diploid genotypes. Our data also indicate a lack of gene flow among polyploid plants of independent origin, even when they co‐occur, suggesting potential reproductive barriers among separate lineages in both polyploid species. 相似文献
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Anisha Prasad Melanie J. F. Croydon‐Sugarman Rosalind L. Murray Asher D. Cutter 《Evolution; international journal of organic evolution》2011,65(1):52-63
Populations of organisms separated by latitude provide striking examples of local adaptation, by virtue of ecological gradients that correlate with latitudinal position on the globe. Ambient temperature forms one key ecological variable that varies with latitude, and here we investigate its effects on the fecundity of self‐fertilizing nematodes of the species Caenorhabditis briggsae that exhibits strong genetically based differentiation in association with latitude. We find that isogenic strains from a Tropical phylogeographic clade have greater lifetime fecundity when reared at extreme high temperatures and lower lifetime fecundity at extreme low temperatures than do strains from a Temperate phylogeographic clade, consistent with adaptation to local temperature regimes. Further, we determine experimentally that the mechanism underlying reduced fecundity at extreme temperatures differs for low versus high temperature extremes, but that the total number of sperm produced by the gonad is unaffected by rearing temperature. Low rearing temperatures result in facultatively reduced oocyte production by hermaphrodites, whereas extreme high temperatures experienced during development induce permanent defects in sperm fertility. Available and emerging genetic tools for this organism will permit the characterization of the evolutionary genetic basis to this putative example of adaptation in latitudinally separated populations. 相似文献
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Life History Evolution in the Genus Trillium 总被引：1，自引：0，他引：1