印度瓜野螟种群的增长力及其密度制约

在养虫室内群体饲养条件下,对印度瓜野螟种群动态的测定结果表明:第二代和第三代的种群内禀增长力(rm)分别为0.0792和0.0487,它们的累计产卵率随时间而表现出逻辑斯蒂曲线变化。在相同的生活和取食空间内,幼虫的发育速率和存活率随种群密度的增长而下降;每对成虫的每天产卵量随成虫密度的增加而递减,单对成虫密度下的产卵率比17对成虫密度下的产卵率高达18倍左右。     

寄生3种夜蛾卵的夜蛾黑卵蜂种群增长潜能

夜蛾黑卵蜂是草地贪夜蛾卵期的一种重要寄生性天敌,适宜的寄主是实现其规模化繁育及应用的基础。本文应用实验种群生命表方法,分析、评价了草地贪夜蛾、斜纹夜蛾及甜菜夜蛾这3种夜蛾卵上夜蛾黑卵蜂的生长发育及种群增长潜能。结果表明,夜蛾黑卵蜂在3种夜蛾卵上均能顺利完成幼期发育且出蜂日期较为整齐,羽化当日即为产卵高峰日,羽化后3 d内的寄生卵量占总产卵量的80%以上。子代羽化率介于77.90%～85.56%之间,雌性比率介于0.53～0.59之间。不同寄主繁育的夜蛾黑卵蜂雄蜂后足胫节长度无明显差异,但以甜菜夜蛾卵繁育的雌蜂的后足胫节最长(152.00μm),斜纹夜蛾卵繁育的次之(146.33μm),草地贪夜蛾卵繁育的最短(142.67μm)。以甜菜夜蛾卵繁育的夜蛾黑卵蜂的内禀增长率(r_m)、净生殖力(R₀)及周限增长率(λ)均最高,分别为0.3486、57.94和1.4171,以斜纹夜蛾卵繁育的次之(r_m,0.3091;R₀,49.60;λ,1.3623),而以草地贪夜蛾卵繁育的最小(r_m,...     

大丰自然保护区麋鹿种群增长模型以及种群密度对种群增长影响的研究

创建了一个关于大丰自然保护区半散养麋鹿种群增长的Logistic模型,该模型准确地预测了麋鹿种群的增长规律.作者通过对比和分析相关数据揭示了种群密度对糜鹿种群增长的影响并给出两个导致种群增长发生改变的临界值.     

大丰麋鹿种群的增长与管理

大丰自然保护区于１９８６年引入麋鹿３９头,到１９９４年发展为１９１头,其成体平均产仔率为８３．５％,周岁内仔鹿成活率为９１％。周岁后年存活率平均为９７％。根据Ｌｅｓｌｉｅ矩阵模型,到１９９８年,麋鹿将发展到４００余头,接近其环境容纳量,到２０００年将发展到约１６００头。届时它将逐渐达到稳定年龄分布。雌性麋鹿４岁时繁殖价最高。约为新产仔鹿的１．８倍。将麋鹿种群调整到环境容纳量水平上的固定年龄分布后,每年从１～２龄麋鹿中调出约２８只（７０．９６％）。即可维持在种群规模为４００头的固定年龄分布。     

种群增长模型中的增长率和增长速率的比较

针对在一道高考题中出现的种群增长率与高中必修(人教版)教材中增长率的涵义不同,通过介绍种群增长模型的三种类型,旨在辨析增长率和增长速率.     

松嫩草原拂子茅种群密度制约的研究

植物种群的密度制约机制是种群生态学研究的重要内容之一。自６０年代初开始,国外已进行了大量的研究,但国内关于这方面的报道很少。本文研究了松嫩草原低湿地拂子茅种群密度的制约规律,结果表明,拂子茅种群生物量与密度呈极显著正相关,并按ｙ＝９９．６１＋２．４１ｅ－０．０１２ｘ曲线消长。平均个体重和平均个体体积与种群密度也呈极显著相关关系,并分别按ｙ＝４．８９ｘ－０．４７和ｙ＝４．０２ｘ－０．７１幂函数变化。但种群密度与以营养枝高度计算的种群体积没有显著的相关关系。     

)种群密度制约实验的统计分析

本文研究了我国特有、分布区极狭窄的一年生草本植物——杭州石荠苎(Mosla hangchowensis)种群的密度制约规律。结果表明：在生长季内,种群的死亡率与密度密切相关。种群的最适密度为200～1000株/m²左右。不同密度种群的平均株高、开花数等性状随时间的动态关系均符合“logistic”模型。高密度种群中60%左右的个体能完成生活史;低密度种群中80%以上的个体能完成生活史。种群密度较高制约杭州石荠苎的植株形态和繁殖投资。     

温度对萼花臂尾轮虫卵的发育、种群增长和生产量的影响

1981—1983年,在不同的培养温度下,观察了萼花臂尾轮虫(Brachionus calyeiflorus)卵的发育时间、种群的增长并用3种不同方法测算生产量。在5—30℃的培养温度下,轮虫卵的发育时间(D)随温度(T)升高而缩短,其曲线迴归方程为：LnD;=2.0539 0.1097LnT-0.3046(LnT)^2在10,15,20,25℃的培养温度下,从休眠卵孵化出来的孤雌生殖雌体,其繁殖的种群增长曲线都呈“S”形,或称逻辑斯蒂曲线(Logistic curvc)。不同的温度,种群达到高峰所需的时间有所不同,温度高者短,低者长;容纳量(carrying capacity)却随温度增加而有所增加。用线性和指数方法计算轮虫种群的生产量所得的结果相似;而与世代时间方法计算所获得的结果相比,差距很大。这种差距随着温度增加而增加。根据本文的研究结果和文献中报道的数据,获得了在0．6—35．2℃温度范围内,卵的发育时间(D)与温度(-I)之间的迴归方程：LnD=2.1869—0．1919LnT-0.2218(LnT)^2     

萼花臂尾轮虫有性生殖、种群增长和休眠卵产量间的关系

利用种群指数增长和Logistic增长模型,通过计算机模拟研究了萼花臂尾轮虫有性生殖发生的频率,后代中的混交雌体发率对种群增长和休眠卵产量的影响。在所模拟的参数范围内,随有性生殖发生频率由100％减小到20％,获得了大休眠卵产量所需的混交雌体百分率由9％增大到69％,随密度制约作用的增大（环境容纳量K值由1000减小到100）,该混交雌体百分率由18％增大到69％,休眠卵产量由1072．10降低至133．67,种群的内禀增长率与获得最大休眠卵产量所需的混交雌体百分率间呈曲线相关。当有性生殖发生得越频繁,种群增长所受的密度制约作用较小时,后代中10％－30％的个体为混交雌体时的种群中休眠卵产量较大。     

二个新的种群增长方程

本文提出了二个新的种群增长方程,方程Ⅰ和方程Ⅱ．对Gause的草履虫实验数据的拟合结果表明,这二个方程与逻辑斯谛方程相比,可以有效地降低拟合的残差平方和．     

Different paths to sexual size dimorphism in two praying mantids,Pseudomantis albofimbriata and Hierodula majuscula

Sexual size dimorphism （SSD） is widespread among diverse animal taxa and has attracted the attention of evolutionary biologists for over a century. SSD is likely to be adaptive and the result of divergent selection on different size optima for males and females, given their different roles in reproduction. The developmental trajectory leading to SSD may help us to understand how selection acts on male and female size. Here, we describe the growth and development of two Australian praying mantids, Pseudomantis albofimbriata and Hierodula majuscula including the number of moults, time to adulthood, size at each moult, and the degree of SSD. While both species exhibit the common pattern of female-biased SSD, the number of moults required for individuals to reach adulthood differed between males and females and between species. Despite their larger adult size, P. albofimbriata females require fewer moults and less time than males to reach adulthood, but are significantly larger than males from the second instar onwards. In contrast, H. majuscula males reached adulthood in fewer moults, and less time than females, however males and females did not differ in size until females went through their final moult into adulthood. H. majuscula also required more time and more moults to reach adulthood than 17. albofimbriata. We discuss these different developmental pathways in light of the existing knowledge of reproductive biology for each species. We also suggest that these differences may relate to the different phenologies that occur in strongly seasonal temperate environments compared with those in the tropics. This study provides evidence that SSD can result from two different patterns of growth and development in closely related species.     

Mnemonic factors in a learning process of praying mantids

Adult female mantids (Stagmatoptera biocellata) learn not to attack a black star figure in movement. The influence of different mnemonic factors in the aquisition, the speed, and/or the retention of this learning was tested. Results demonstrate that learning depends on the number of trials, the span of the intersession period, the presence or absence of a load on the mantid's head, and the greater or smaller constancy in the stimulus presentation. On the other hand, the presence or absence of an intertrial interval seems to have no influence on the process. Mantids without a load on their heads, i.e. without an experimental trick that facilitates learning, can only overcome their strong tendency to attack when two conditions are fulfilled: a massive number of presentations (80 trials, at least) and great constancy in the stimulus presentation. Three principal points are discussed concerning these results: (1) The survival value of these findings. (2) The importance of mnemonic factors to minimize in an experimental design the difference in the learning concomitants between a group that learns and another group which does not learn. (3) The classification of this learning process as a case of negative reinforced conditioning and not one of simple habituation, because there is a punishment effect during every strike due to the load on the mantid's head.     

Episodes of unpalatable prey reduce consumption and growth of juvenile praying mantids

Third-instar praying mantids (Tenodera sinensisSaussure: Mantidae) were fed either a sequence of unpalatable milkweed bugs (Oncopeltus fasciatusDallas: Lygaeidae) and palatable fruit flies (Drosophila melanogasterMeigen: Drosophilidae) or a control diet of palatable flies only. Mantids fed a sequence of 3 days of unpalatable bugs and 4 days of palatable flies took, on average, 5 days longer to develop to the fourth instar than the controls, and consequently, their growth rate was less than that of the controls. They ate 10–15 unpalatable bugs in that time, but also, because the stadium was prolonged, they ended up eating as many flies as the faster-growing controls and therefore attained similar biomass. Mantids subjected to episodes of 2 days with unpalatable bugs followed by 4 days of flies had reduced growth rates that were a function of both more time spent in the stadium and less weight gained than the controls. Mantids subjected to episodes of 1 day with unpalatable bugs followed by 4 days of flies did not gain as much weight as the controls but had similar growth rates. Mantids fed unpalatable bugs on Days 1 and 6 and palatable flies on the other days and mantids fed flies for 4 days and then 1 day without food grew at the same rate. In this case, eating unpalatable prey for 2 days of 7 (with 7 days = average stadium duration) slowed weight gain as much as missing food for a day. We conclude that, depending on the sequence, episodes (in this case, 1 or more days) of eating unpalatable prey can reduce the daily rate of consumption sufficiently to have a negative impact on biomass gained, stadium duration, and growth rate.     

Contrasting scales of oviposition and parasitism in praying mantids

We report on spatial patterns of parasitism of oothecae (egg cases) of praying mantises (Stagmomantis limbata) by torymid wasps, Podagrion spp. Using collections of mapped mantid oothecae from Riparian sites in the Sonoran desert and Grassland sites in the Chiricahua Mountains (both in Arizona, USA), we characterized the spatial distributions of oothecae and parasitism. The likelihood of an egg case suffering some parasitism was higher at Grassland sites, which had high oothecal densities, than at low-density Riparian sites. However, experimental isolation of Grassland oothecae to densities comparable to Riparian sites reduced parasitism rates. At Riparian sites, parasitized oothecae exhibited on average the same extent of parasitism as parasitized oothecae at high densities but with much greater variation. Indeed, large fractions of Riparian oothecae suffered both severe (>50%) and light (<20%) parasitism, whereas most parasitized Grassland oothecae suffered intermediate levels of parasitism. Analysis of first nearest neighbor distances indicated that the parasite load of an ootheca did not depend on its immediate isolation. However, extending the analysis to include subsequent nearest neighbors (using a technique from spatial statistics called the R(K) function), we found that even though oothecae of S. limbata were spatially clustered, some oothecae in a (statistically defined) cluster escaped parasitism when overall oothecal densities were low. This pattern suggests that when oothecae are sparsely distributed, Podagrion wasps exploit only a fraction of the oothecae available locally, even though the oothecae are strongly aggregated relative to their overall density. We suggest this lack of congruency in the scales of oothecal deposition and parasitism at low densities (which is absent when oothecae are at high densities) may be explained in part by behavioral aspects of the parasite's reproduction, including increased host fidelity by relatively sedentary female parasites. Received: June 13, 2000 / Accepted: October 16, 2000     

Geographic variation in genital morphology of Ciulfina praying mantids

Geographic variation in morphological traits is widespread and important to our current understanding of evolutionary processes. Although male genitalia are perhaps the most divergent morphological traits in animals, geographic variation in genital traits has received little attention and the mechanism driving such variation is unclear. The species isolation hypothesis of genital evolution makes explicit predictions about geographic variation in genitalia predicting patterns of genital divergence that reflect the risk of mating with related but incompatible species. The sexual selection and pleiotropy hypotheses, however, predict general levels of geographic variation that reflect divergent sexual selection pressures or genetic drift. To test these predictions, we investigated geographic variation in genital morphology in the praying mantid genus Ciulfina (Mantodea: Liturgusidae) using elliptic Fourier analysis. We found significant levels of geographic variation in the genital morphology of four Ciulfina species irrespective of the relative proximity of different populations to contact zones with other species. These results reject the species isolation hypothesis, and instead support either the sexual selection or pleiotropy hypotheses to explain patterns of genital evolution in this genus.     

The effects of initial population density on the competition for limiting nutrients in two freshwater algae

Eighteen long-term competition experiments were performed on two freshwater algae, a blue-green alga, Anabaena flos-aquae, and a diatom, Cyclotella sp., under controlled light and temperature conditions and various nutrient limitations. As predicted, Anabaena displaced Cyclotella when nitrate was in short supply to both species, whereas Cyclotella became dominant when both species were phosphate-limited. The two species stably coexisted when phosphate and silicate were limited. Anabaena either displaced or coexisted with Cyclotella when nitrate and phosphate or nitrate, phosphate and silicate were limited, depending on their initial density ratios. This study revealed strong effects of initial population densities on the outcomes of algal competition for limiting nutrients.