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81.
Two species of the green alga genusCaulerpa are considered as invasive in Tunisia:Caulerpa racemosa andC. taxifolia. C. racemosa is found in a many new localities at the central and southern Tunisian coast, and even in the North of the country in colder
water. These new observations lead to the hypothesis of the multiplicity of the origins of the introduction of the species
and suggest possible invasive potentialities. The general thallus, and more particularly the number, the shape as well as
the arrangement of ramelli on fronds allowed us to identify four morphologically different groups. These groups could be either
different systematic entities or polymorphic variations of the same taxon due to different ecological conditions.Caulerpa taxifolia was observed for the first time in Tunisia at the roadstead of Sousse in the beginning of the year 2000. It is recognized
as identical to that found in the other Mediterranean localities (GenBank number AJ228960). Up to the end of March 2000, a
submarine prospecting campaign revealed an affected area of about 350 ha in front of 2 km of coast. Colonies ofCaulerpa taxifolia disseminating in this area appear in isolated spots. form, In the growing stage, they form surfaces varying between 0.5 to
6 m2 and located 20 to 100 m from each other. The total covered surface was estimated to be between 0.5 and 1 ha. 相似文献
82.
Qinghui Sun Juan Li Chen Wang Anqi Chen Yanli You Shupeng Yang Huihui Liu Guibin Jiang Yongning Wu Yanshen Li 《Frontiers of Environmental Science & Engineering》2022,16(1):1
83.
Wolf U. Blanckenhorn James W. A. Grant Daphne J. Fairbairn 《Behavioral ecology and sociobiology》1998,42(1):63-70
The monopolization of resources plays an important theoretical role in the literature on competition for food and mates.
We used 12 groups of male water striders (Aquariusremigis) to: (1) test the general prediction that monopolization of both food and mates decreases as the temporal clumping of resources
increases, (2) compare the efficiency of two indices of resource monopolization, coefficient of variation and Q (Ruzzante et al. 1996), and (3) quantitatively assess the resource queue model of Blanckenhorn and Caraco (1992). Each group
of six males competed for both food items and mates released from the upstream end of a laboratory stream. The mean inter-arrival
time for resource units (food or females) was 10 min, with four levels of temporal clumping (variance in inter-arrival time:
0, 25, 50 or 320 min2). As predicted, the monopolization of both food and mates decreased as the temporal clumping of resource arrival increased,
although monopolization was greater for food than for mates. Q detected the difference in monopolization of food and mates, whereas the coefficient of variation did not, because Q is independent of mean resource abundance. The resource queue model successfully predicted monopolization of both resource
types, explaining 89% and 76% of variation in the proportion of food and mates acquired by the six males. The success of the
model suggests that the scaling of handling time to the variance in resource inter-arrival time should play an important role
in any general theory of resource monopolization.
Received: 28 February 1997 / Accepted after revision: 26 September 1997 相似文献
84.
Marion Valeix Hervé Fritz Andrew J. Loveridge Zeke Davidson Jane E. Hunt Felix Murindagomo David W. Macdonald 《Behavioral ecology and sociobiology》2009,63(10):1483-1494
A central question in the study of predator–prey relationships is to what extent prey behaviour is determined by avoidance
of predators. Here, we test whether the long-term risk of encountering lions and the presence of lions in the vicinity influence
the behaviour of large African herbivores at waterholes through avoidance of high-risk areas, increases in group size, changes
in temporal niche or changes in the time spent in waterhole areas. In Hwange National Park, Zimbabwe, we monitored waterholes
to study the behaviour of nine herbivore species under different risks of encountering lions. We radio-collared 26 lions in
the study area which provided the opportunity to monitor whether lions were present during observation sessions and to map
longer-term seasonal landscapes of risk of encountering lions. Our results show that the preferred prey species for lions
(buffalo, kudu and giraffe) avoided risky waterholes. Group size increased as encounter risk increased for only two species
(wildebeest and zebra), but this effect was not strong. Interestingly, buffalo avoided the hours of the day which are dangerous
when the long-term and short-term risks of encountering lions were high, and all species showed avoidance of waterhole use
at night times when lions were in the vicinity. This illustrates well how prey can make temporal adjustments to avoid dangerous
periods coinciding with predator hunting. Additionally, many herbivores spent more time accessing water to drink when the
long- and short-term risks of encountering lions were high, and they showed longer potential drinking time when the long-term
risk of encountering lions was high, suggesting higher levels of vigilance. This study illustrates the diversity of behavioural
adjustments to the risk of encountering a predator and how prey respond differently to temporal variations in this risk. 相似文献
85.
In order to measure groundwater age and design nuclear waste disposal sites, it is important to understand the sorption behavior of tritium on soils. In this study, batch tests were carried out using four soils from China: silty clays from An County and Jiangyou County in Sichuan Province, both of which could be considered candidate sites for Very Low Level Waste disposal; silty sand from Beijing; and loess from Yuci County in Shanxi Province, a typical Chinese loess region. The experimental results indicated that in these soil media, the distribution coefficient of tritium is slightly influenced by adsorption time, water/solid ratio, initial tritium specific activity, pH, and the content of humic and fulvic acids. The average distribution coefficient from all of these influencing factors was about 0.1-0.2 mL/g for the four types of soil samples. This relatively modest sorption of tritium in soils needs to be considered in fate and transport studies of tritium in the environment. 相似文献
86.
Jan Peters Niko E.C. Verhoest Roeland Samson Marc Van Meirvenne Liesbet Cockx Bernard De Baets 《Ecological modelling》2009
Ensemble learning techniques are increasingly applied for species and vegetation distribution modelling, often resulting in more accurate predictions. At the same time, uncertainty assessment of distribution models is gaining attention. In this study, Random Forests, an ensemble learning technique, is selected for vegetation distribution modelling based on environmental variables. The impact of two important sources of uncertainty, that is the uncertainty on spatial interpolation of environmental variables and the uncertainty on species clustering into vegetation types, is quantified based on sequential Gaussian simulation and pseudo-randomization tests, respectively. An empirical assessment of the uncertainty propagation to the distribution modelling results indicated a gradual decrease in performance with increasing input uncertainty. The test set error ranged from 30.83% to 52.63% and from 30.83% to 83.62%, when the uncertainty ranges on spatial interpolation and on vegetation clustering, respectively, were fully covered. Shannon’s entropy, which is proposed as a measure for uncertainty of ensemble predictions, revealed a similar increasing trend in prediction uncertainty. The implications of these results in an empirical distribution modelling framework are further discussed with respect to monitoring setup, spatial interpolation and species clustering. 相似文献
87.
焦荣华 《湖南环境生物职业技术学院学报》2009,15(3):24-27
分析了湖南衡阳地区乙型肝炎病毒基因型分布特征,并探讨HBV各基因型与血清HBVDNA水平之间的关系.采用荧光定量PCR结合TaqmanMGB探针技术,对湖南衡阳地区164份乙型肝炎患者血清中的HBVDNA进行基因分型和定量检测.结果164例血清中,C型110A.(67.1%),B、C型37人(22.3%),B型8人(5.1%),D型1人(0.6%),A型1人(0.6%).C型与B、C混合型在HBVDNA水平上存在显著差异(t=2.433,P〈0.05),B、C混合型的HBVDNA水平明显高于C型.由此得出湖南衡阳地区HBV基因型以C型为主、B、C混合型次之,B型较少,D型、A型极少;B、C混合型患者的HBVDNA数量水平显著高于C型.表1.参11. 相似文献
88.
模糊综合评价法在水质变化和水体管理中的应用 总被引:1,自引:0,他引:1
应用模糊数学中的模糊综合评价法,对徐州市的地面水体的水质变化趋势进行了探讨,结果表明模糊综合评价法能及时发现水质恶化现象,对水体的管理具有指导作用. 相似文献
89.
The age at which worker honey bees begin foraging varies under different colony conditions. Previous studies have shown that
juvenile hormone (JH) mediates this behavioral plasticity, and that worker-worker interactions influence both JH titers and
age at first foraging. These results also indicated that the age at first foraging is delayed in the presence of foragers,
suggesting that colony age demography directly influences temporal division of labor. We tested this hypothesis by determining
whether behavioral or physiological development can be accelerated, delayed, or reversed by altering colony age structure.
In three out of three trials, earlier onset of foraging was induced in colonies depleted of foragers compared to colonies
depleted of an equal number of bees across all age classes. In two out of three trials, delayed onset of foraging was induced
in colonies in which foragers were confined compared to colonies with free-flying foragers. Finally, in three out of three
trials, both endocrine and exocrine changes associated with reversion from foraging to brood care were induced in colonies
composed of all old bees and devoid of brood; JH titers decreased and hypopharyngeal glands regenerated. These results demonstrate
that plasticity in age-related division of labor in honey bee colonies is at least partially controlled by social factors.
The implications of these results are discussed for the recently developed ‘‘activator-inhibitor” model for honey bee behavioral
development.
Received: 8 November 1995/Accepted after revision: 10 May 1996 相似文献
90.
John?YangEmail author Jianguo?Sun David?Hammer Robert?Blanchar 《Environmental Chemistry Letters》2004,2(3):159-162
Soil pH, a log-transformed form of hydrogen ion (H+) activity, is often used for various statistics. However whether soil pH meets the requirement of distribution normality for statistical analyses is unknown. We studied the statistical suitability of both soil pH and H+ activity by examining their distribution normalities. Results show that the variability of H+ activity is higher and its distribution is skewer, which is significantly different from the normal and soil pH, regardless of soil conditions and analytical methods. Here we demonstrate that soil pH is more appropriate than the H+ activity for performing statistical analysis in terms of distribution normality. 相似文献