共查询到20条相似文献，搜索用时 62 毫秒
1.
基于Kendall-Goodman模型,提出了一个两性具有不同生理性态的随机配对的两性模型．如果不考虑密度制约因素,那么模型存在一个全局渐近稳定的指数解;如果考虑密度制约因素,对于给定的一个出生函数,得到了唯一正平衡态存在及全局稳定的充要条件．结论表明,无论是否考虑密度制约因素,种群的性比总是稳定的． 相似文献
2.
棉蚜田间种群特定死亡率分析戈峰丁岩钦（中国科学院动物研究所,北京１０００８０）ＡｎａｌｙｓｉｓｏｆｔｈｅＴｉｍｅ┐ｓｐｅｃｉｆｉｃＭｏｒｔａｌｉｔｙｏｆＣｏｔｔｏｎＡｐｈｉｄ（Ａｐｈｉｓｇｏｓｓｙｐü）Ｐｏｐｕｌａｔｉｏｎ．ＧｅＦｅｎｇ,ＤｉｎｇＹａ... 相似文献
3.
4.
计算机模拟昆虫的种群数量动态变化对于昆虫种群预测和害虫治理十分重要。本文介绍以年龄-龄期两性生命表(age-stage, two-sex life table)为基础,利用计算机模拟预测昆虫的种群动态、种群捕食、寄生和取食的波动、害虫防治时机以及模拟的变异性。利用年龄-龄期两性生命表软件(程式)TWOSEX-MSChart与捕食率软件CONSUME-MSChart分析生命表与捕食率数据,再将分析结果用模拟软件TIMING-MSChart模拟预测种群增长过程中龄期结构以及捕食能力、寄生能力和取食能力的变化。依据种群动态可以预测害虫危害、天敌捕食、寄生蜂寄生能力,再用这些数据确定杀虫剂的施药时机和施药次数,预测生物防治中天敌释放的适当时机、释放数量和释放次数等;同时还可以依据生命表的变异性,利用自我重复取样(bootstrap)技术得到的2.5和97.5百分位(percentiles)或其他百分位的生命表预测种群增长的不确定性。借助基于两性生命表理论的计算机模拟可以预测害虫种群增长以及化学防治和生物防治的最佳时期,以达到经济有效的害虫综合治理,并为农业可持续性提供理论与技术支撑。 相似文献
5.
网湖似刺鳊Ju种群生长和死亡率研究 总被引：7，自引：1，他引：7
本文根据６６９尾标本,研究长江中游网湖小型经济鱼类似刺鳊Ｊｕ的种群生长和死亡率,从理论推导证明,鱼类的生长拐点与其临界年龄是一致的,并据以对网湖似刺鳊Ｊｕ等小型经济鱼类的合理渔业对策问题进行了初步分析讨论。 相似文献
6.
林麝是濒危资源动物,林麝驯养是保育濒危林麝资源及可持续利用麝香的有效方式。基于对2001至2012年间的陕西凤县林麝驯养的监测和调查,分析了其种群动态、性比和年龄结构。结果表明,陕西凤县的林麝驯养在近10余年获得了快速发展,全县共有150余个麝场,麝场数呈指数式增长,增长率达27.33%,但其平均驯养规模无明显增长,平均存栏种群仅为16.38头。凤县的驯养麝种群总体增长近似指数式增长,增长率达27.22%,目前存栏种群已达3712头。区分性别和年龄,各亚群的增长均呈指数式增长,幼年麝的增长率(30.30%)高于成年麝(27.16%),雄麝的增长率(28.30%)高于雌麝(27.78%)。在2001至2012年间,幼麝种群的雌雄性比((102.64±3.15)%,n=12)和成年麝种群的雌雄性比((100.85±2.585)%,n=10)均显著偏雌(P0.01),但幼麝、成年麝种群间的性比差异不显著(P0.05)。在2005年及2010—2012年间,幼麝(0.5岁龄)占种群的比例为31.91%,亚成体麝(1.5岁龄)占种群的比例为21.11%,成麝(2.5—12.5岁龄)比例为42.72%,老年麝(13.5岁龄及以上)仅占种群的4.26%。合并年龄分析,育龄前个体(幼麝和亚成体麝)的平均比例为53.02%,表明凤县驯养林麝属快速增长种群,其增长潜力较大。在林麝驯养实践中,管理部门可制定准入制度或适当重组现有麝场,促进较大的驯养种群构建,并建立通畅的麝香交易渠道,控制林麝种源的过热交易,以利于林麝驯养种群的性比平衡及可持续的繁育、增长。 相似文献
7.
为分析黑龙江省完达山林区马鹿种群生存状态,制定科学有效地保护措施,从分子水平研究了种群数量和性比。2006、2007两年冬季跟踪马鹿足迹链,于五泡林场共搜集210份粪便,以成功提取DNA的167份作为分析样本。通过多态性较高的7个微卫星位点进行了基因分型分析,显示167份粪便DNA分属66只个体。基于非损伤性标志重捕法,统计出林场内马鹿数量2a平均47(39—60)只,密度0.302(0.251—0.386)只/km2,与2002年大样方法调查结果相比有减无增。SRY基因性别鉴定显示,种群雌雄性比1.00∶2.00(22♀,44♂),存在较多雄性个体,分析认为偷猎是导致性比失衡的最主要原因。数量的持续下降和性比失衡提示完达山林区马鹿种群数量的恢复需要更好地保护工作。 相似文献
8.
沈承烨;禹洋;雷书瑶;向左甫 《兽类学报》2025,45(1):70-77
在国内现存的6个猕猴亚种中;福建亚种(Macaca mulatta littoralis)是受关注较少的亚种之一。本研究在湖南武陵源风景区;通过野外跟踪调查;在个体识别的基础上对该地区猕猴种群大小、交配和出生季节进行了调查研究;旨在探究猕猴福建亚种的种群结构和繁殖参数。结果表明:(1)研究地区内现有18个猴群;群体平均大小为(47.78 ±22.51)只(范围16~79);总体性比(雄/雌)为1∶1.57;成年个体为1∶2.47;亚成年个体为1∶3.25;青少年个体为1∶1.08;婴猴为1∶1.05;(2)射精交配发生在10月到翌年2月;11月交配频次达到顶峰;(3)出生季节分布在3—6月;4—5月为高峰期;平均出生日期为4月28日;出生日期中位数为5月1日;标准差为19.11 d;表明猴群为季节性繁殖类型;符合脉冲模型;(4)种群出生率为66.27%;死亡率为1.80%;种群增长率为18.09%。本研究结果可为武陵源风景区猕猴的生态、行为及保护生物学等研究提供基础数据。 相似文献
9.
10.
11.
Emily G. Butka Steven Freedberg 《Evolution; international journal of organic evolution》2019,73(1):99-110
Spatial structure has been shown to favor female‐biased sex allocation, but current theory fails to explain male biases seen in many taxa, particularly those with environmental sex determination (ESD). We present a theory and accompanying individual‐based simulation model that demonstrates how population structure leads to male‐biased population sex ratios under ESD. Our simulations agree with earlier work showing that the high productivity of female‐producing habitats creates a net influx of sex‐determining alleles into male‐producing habitats, causing larger sex ratio biases, and lower productivity in male‐producing environments (Harts et al. 2014). In contrast to previous findings, we show that male‐biasing habitats disproportionately impact the global sex ratio, resulting in stable male‐biased population sex ratios under ESD. The failure to detect a male bias in earlier work can be attributed to small subpopulation sizes leading to local mate competition, a condition unlikely to be met in most ESD systems. Simulations revealed that consistent male biases are expected over a wide range of population structures, environmental conditions, and genetic architectures of sex determination, with male excesses as large as 30 percent under some conditions. Given the ubiquity of genetic structure in natural populations, we predict that modest, enduring male biased allocation should be common in ESD species, a pattern consistent with reviews of ESD sex ratios. 相似文献
12.
《African Journal of Aquatic Science》2013,38(1):81-85
Aspects of the reproductive biology and population structure of Labeo senegalensis were investigated in the Ouémé River between April 2005 and March 2006. Reproductive strategy was investigated using gonadosomatic index, ovarian structure and fecundity. Average size-at-first-maturity (L 50) was estimated at 29 cm TL for females and 25.7 cm TL for males. The average sex ratio (1:0.96) was not significantly different from unity. Oocyte diameter frequency distribution suggests synchronous development with a single total spawning. Absolute fecundity ranged between 12 948 and 74 832 eggs. Labeo senegalensisis a highly fecund fish that presents a seasonal cycle of reproduction from May to October during the rainy season. 相似文献
13.
David E. McCauley Marcus T. Brock 《Evolution; international journal of organic evolution》1998,52(1):30-36
In gynodioecious plants the selective processes that determine the relative number of female and hermaphroditic individuals are often frequency dependent. Frequency-dependent fitness can occur in the two sexes through a variety of mechanisms, especially given pollen limitation and inbreeding depression when hermaphrodites are rare. Frequency dependence in several components of the fitness of female and hermaphroditic Silene vulgaris was tested in experiments in which the relative numbers of the two sexes was varied among 12 artificial populations. In females, the proportion of flowers that set fruit covaried positively among populations with the frequency of hermaphrodites in two separate experiments, whereas the number of flowers/plant covaried negatively in one case. In hermaphrodites, the number of seeds/fruit covaried positively with the frequency of hermaphrodites, whereas the fitness of hermaphrodites estimated through pollen transfer covaried negatively. The results are discussed as they relate to the selective maintenance of gynodioecy in S. vulgaris and in light of a recent model of the effect of population structure on selection in gynodioecious systems. 相似文献
14.
Maternal sex ratio distorters (MSDs) are selfish elements that enhance their transmission by biasing their host's sex allocation in favor of females. While previous models have predicted that the female‐biased populations resulting from sex ratio distortion can benefit from enhanced productivity, these models neglect Fisherian selection for nuclear suppressors, an unrealistic assumption in most systems. We used individual‐based computer simulation modeling to explore the intragenomic conflict between sex ratio distorters and their suppressors and explored the impacts of these dynamics on population‐level competition between species characterized by MSDs and those lacking them. The conflict between distorters and suppressors was capable of producing large cyclical fluctuations in the population sex ratio and reproductive rate. Despite fitness costs associated with the distorters and suppressors, MSD populations often exhibited enhanced productivity and outcompeted non‐MSD populations in single and multiple‐population competition simulations. Notably, the conflict itself is beneficial to the success of populations, as sex ratio oscillations limit the competitive deficits associated with prolonged periods of male rarity. Although intragenomic conflict has been historically viewed as deleterious to populations, our results suggest that distorter–suppressor conflict can provide population‐level advantages, potentially helping to explain the persistence of sex ratio distorters in a range of taxa. 相似文献
15.
利用2012年2月至2013年1月在钱塘江桐庐段水域的渔获物中采集的样本,对该水域花（Hemibarbus maculatus Bleeker）种群的叉长和体质量组成,性别组成和性比、年龄组成等渔业种群结构特征进行了初步研究。结果表明,渔获群体的叉长范围为11.2~33.1 cm,平均叉长为（20.2±3.45）cm;体质量范围为26.0~540.8 g,平均体质量为（171.6±81.9）g。雌性个体大于雄性个体,雌性渔获群体的平均叉长为（23.5±3.58）cm,平均体质量为（183.2±79.87）g;雄性渔获群体的平均叉长为（22.7±3.77）cm,平均体质量为（168.8±78.99）g。雌性群体数量多于雄性群体数量,雌、雄性比约为1.47∶1。渔获群体由4个年龄组组成,以2龄为主。 相似文献
16.
The female-biased sex ratio in the genus Silene is the most widely documented example of sex ratio bias in plants. It has recently been shown that the genetic basis of sex ratio in this species involves a system of sex ratio distorters and restorers, but it is not known if these genetic elements are of fundamental importance in natural populations. I crossed plants from natural populations with known testers to examine the frequencies of sex ratio distorters and restorers in eight populations of S. alba, and to determine the extent that these elements are responsible for the sex ratio variation in nature. The genetic basis of sex ratio varied from one population to another, suggesting that sex ratio evolution occurs over a relatively small spatial scale and is asynchronous among local demes. The resulting variation in the frequency of sex ratio alleles among populations explained most of the sex ratio variation seen in nature, which suggests that the ecology and evolution of this trait in natural populations is governed primarily by underlying dynamics of selfish genetic elements. The possible causes and the evolutionary consequences of population structure at genes controlling sex ratio are discussed, as are the implications of these results for the overall importance of selfish genetic elements in natural populations. 相似文献
17.
GREGORY D. D. HURST MICHAEL E. N. MAJERUS LINDA E. WALKER 《Biological journal of the Linnean Society. Linnean Society of London》1993,49(2):195-202
Adalia bipunctata , the two spot ladybird, is polymorphic for a cytoplasmically inherited element which produces female-biased sex ratios by effecting the death of male offspring during embryogenesis. The levels of this element were assessed in Cambridge populations. Six out of 82 females tested showed both a female-biased sex ratio and low egg hatch rates consistent with the presence of this element. Population sex ratios were assessed by collecting pupae from the Cambridge area. The population sex ratio was found to be 1.15: 1, female biased, significantly different from 1:1, and consistent with predictions based on a model incorporating the observed level of the sex ratio element in the population. 相似文献
18.
19.
Many organisms display oscillations in population size. Theory predicts that these fluctuations can be generated by predator–prey interactions, and empirical studies using life model systems, such as a rotifer-algae community consisting of Brachionus calyciflorus as predator and Chlorella vulgaris as prey, have been successfully used for studying such dynamics. B. calyciflorus is a cyclical parthenogen (CP) and clones often differ in their sexual propensity, that is, the degree to which they engage into sexual or asexual (clonal) reproduction. Since sexual propensities can affect growth rates and population sizes, we hypothesized that this might also affect population oscillations. Here, we studied the dynamical behaviour of B. calyciflorus clones representing either CPs (regularly inducing sex) or obligate parthenogens (OPs). We found that the amplitudes of population cycles to be increased in OPs at low nutrient levels. Several other population dynamic parameters seemed unaffected. This suggests that reproductive mode might be an important additional variable to be considered in future studies of population oscillations. 相似文献
20.
Rahel Sollmann;Tim Caro; 《Ecology and evolution》2024,14(8):e70168
Species experience a variety of environmental and anthropogenic conditions across their ranges leading to spatial variation in population dynamics. Understanding population dynamics under different conditions is important but it is challenging to allocate limited effort to spatial and temporal subpopulation monitoring. Using GLMMs, we analyze survey data of a metapopulation of coconut crabs spanning 7 years and 15 sites in and near the Pemba archipelago, Zanzibar, to estimate trends in population size (based on catch per unit effort), weight and sex ratio at the meta- and subpopulation level and investigate anthropogenic drivers of these trends. We found that the overall metapopulation has remained stable in terms of size and composition over the survey period, but observed diverging trends in population size and sex ratio at some subpopulations. Formal protection of sites was associated with positive population trends. Of nine sites for which we could estimate site-specific trends, three showed increasing and two decreasing trends, whereas four sites had stable subpopulations. Although anthropogenic factors affected the average weight, and the incidence of small and large individuals, we found no temporal trends in any weight-related measures. Furthermore, there were no apparent patterns between weight-related measures and subpopulation trends. The metapopulation was biased toward males, and exploitation appeared to be associated with declining trends in the proportion of females, likely an artifact of a strong decline in the proportion of females in one of only two exploited sites in the dataset. Educational campaigns implemented in 2020 at six sites were not related to higher population sizes in later surveys. The variable trends in subpopulation sizes and composition highlight the need for spatially replicated monitoring in metapopulations. The analyses further provide a detailed baseline for future subpopulation studies of this vulnerable species in one of its last remaining metapopulations in the Western Indian Ocean. 相似文献