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321.
VINCENT DEVICTOR ‡ ROMAIN JULLIARD DENIS COUVET ALEXANDRE LEE† FRÉDÉRIC JIGUET 《Conservation biology》2007,21(3):741-751
Abstract: We studied the community richness and dynamics of birds in landscapes recently affected by urbanization to test the prediction that biotic communities living in degraded landscapes are increasingly composed of generalist species. We analyzed bird communities in 657 plots monitored by the French Breeding Bird Survey from 2001 to 2005, accounting for the probability of species detection and spatial autocorrelation. We used an independent land-cover program to assess urbanization intensity in each FBBS plot, from 1992 to 2002. We found that urbanization induced community homogenization and that populations of specialist species became increasingly unstable with increasing urbanization of the landscape. Our results emphasize that urbanization has a substantial impact on the spatial component of communities and highlight the destabilizing effect of urbanization on communities over time. These results illustrate that urbanization may be a strong driving force in functional community composition and that measuring community homogenization is a powerful tool in the assessment of the effects of landscape changes and thus aides sustainable urban planning. 相似文献
322.
Juliana Valencia Elena Solís Gabriele Sorci Carlos de la Cruz 《Behavioral ecology and sociobiology》2006,60(3):399-404
In cooperatively breeding species, helpers may contribute to the success of the brood by increasing the number of independent offspring, but also, they may affect offspring condition and, hence, their survival and recruitment into the breeding population. This second type of benefits is rarely included in theoretical models or assessed in field studies. Immune response is a good proxy of individual quality and fitness, and there is good evidence that the performance of the immune system of chicks during the nestling phase is related to their chances of survival and future reproduction. However, no study has so far explored whether helpers at the nest might contribute to enhance immune functioning of nestlings in species with a cooperative breeding system. Here we investigate this issue in the azure-winged magpie (Cyanopica cyanus) and found for the first time a positive correlation between the number of helpers at nest and the cell-mediated immune response of nestlings. This effect was not explained by a general improvement of body condition of chicks because it was independent of individual variation in body mass or tarsus length. Our results suggest that helping can have subtle effects on the quality of offspring that may influence their survival and future reproduction. 相似文献
323.
J. Haydock Patricia G. Parker Kerry N. Rabenold 《Behavioral ecology and sociobiology》1996,38(1):1-16
We investigated parentage using multilocus DNA fingerprinting for 222 juveniles produced during 99 group-years in the bicolored
wren Campylorhynchus griseus, a cooperatively breeding bird of the Venezuelan savanna. Young adult bicolored wrens (auxiliaries) remain in their natal
territories and substantially enhance the production of young there. We have previously used behavioral indicators of dominance
by a single male/female pair (principals) to infer breeding status, resulting in the commonly applied model of helping in
which current fitness accrues to auxiliaries only indirectly, in proportion to their relatedness to the principals and the
effect of their assistance on breeding success. Our parentage analysis has demonstrated that 8.6% of the juveniles found on
territories were not produced by the principal pair. Parentage of 4.1% of the juveniles was completely outside the social
group; these appear to result from early dispersal of juveniles rather than from brood parasitism, most likely resulting from
breakup of nearby groups. Principal females mated outside of their group (2.3%), or with an auxiliary male (2.3%), in the
remaining cases of parentage outside the principal pair. No matings were detected between close relatives (e.g. mother-son);
matings detected between the principal female and an auxiliary male followed a typical replacement of the principal female
by an unrelated immigrant female. Our finger-printing results indicate that: (1) current fitness benefits accruing to most
auxiliaries do not exceed their likely reproductive success had they dispersed successfully to a breeding position; (2) nearly
all wren mating is monogamous and (3) behavioral dominants (especially females) can monopolize breeding.
Received: 23 September 1994/Accepted after revision: 10 June 1995 相似文献
324.
Linking Wild and Captive Populations to Maximize Species Persistence: Optimal Translocation Strategies 总被引:2,自引:0,他引:2
BRIGITTE TENHUMBERG§ REW J. TYRE KATRIONA SHEA† HUGH P. POSSINGHAM‡ 《Conservation biology》2004,18(5):1304-1314
Abstract: Captive breeding of animals is widely used to manage endangered species, frequently with the ambition of future reintroduction into the wild. Because this conservation measure is very expensive, we need to optimize decisions, such as when to capture wild animals or release captive-bred individuals into the wild. It is unlikely that one particular strategy will always work best; instead, we expect the best decision to depend on the number of individuals in the wild and in captivity. We constructed a first-order Markov-chain population model for two populations, one captive and one wild, and we used stochastic dynamic programming to identify optimal state-dependent strategies. The model recommends unique sequences of optimal management actions over several years. A robust rule of thumb for species that can increase faster in captivity than in the wild is to capture the entire wild population whenever the wild population is below a threshold size of 20 females. This rule applies even if the wild population is growing and under a broad range of different parameter values. Once a captive population is established, it should be maintained as a safety net and animals should be released only if the captive population is close to its carrying capacity. We illustrate the utility of this model by applying it to the Arabian oryx ( Oryx leucoryx ). The threshold for capturing the entire Arabian oryx population in the wild is 36 females, and captive-bred individuals should not be released before the captive facilities are at least 85% full. 相似文献
325.
重庆库区不同海拔段繁殖鸟类群落的物种多样性 总被引:1,自引:0,他引:1
1996~1997年,对三峡工程重庆库区的鸟类群落的物种组成和种群数量进行了调查,共调查记录库区繁殖鸟类12目40科170种,数量17326只,其中留鸟有104种,占繁殖鸟总数的61.2%,夏侯鸟66种,占38.8%.用秩-多度曲线对不同海拔段的繁殖鸟类群落进行多样性分析的结果显示:1)秩-多度曲线方法的结果比Shannon-Wiener等物种多样性指数更直观,能更全面地反映多样性状况,该曲线可以对不同群落或相同群落在不同时间的物种多样性进行比较,是分析生物多样性的一种最直观的方法;2)人类干扰是影响各海拔段繁殖鸟类群落物种多样性的主要因素,人类干扰越强烈,鸟类群落物种多样性越低.图2表3参20 相似文献
326.
Susan M. Haig Jeffrey R. Walters Jonathan H. Plissner 《Behavioral ecology and sociobiology》1994,34(4):295-303
We examined the genetic relationship among putative parents, offspring, and helpers in 224 red-cock-aded woodpeckers (Picoides borealis) from the Sandhills of North Carolina. Comparison of DNA similarity with a pedigree constructed from 3,823 individually-marked birds observed from 1979 to 1992 provided verification of observed relatedness in the sampled population (R
2 = 0.87, df = 14, P < 0.001). In this population, breeding pairs may or may not have helpers, most of which are males that remain on their natal territory. Our sample included helpers assisting their parents, helpers assisting a related male and an unrelated female, and helpers assisting an unrelated pair. Band by band comparison and examination of similarity among DNA profiles indicated that all offspring from non-helped nests were sired by their putative parents (n = 28 families). Similarly, all but one offspring in helped nests were also sired by their putative parents (n = 16 families). In the exceptional case, the offspring evidently was sired by a male external to the group. Analysis of similarity values supported the conclusion that matings by helpers or extra-group males are rare or non-existent. Our results indicate that in this species advantages gained by individuals remaining on their natal territories as helpers do not generally include siring offspring.
Correspondence to: S. Haig 相似文献
327.
中国猪的优良种性及其对世界养猪业的贡献 总被引:3,自引:0,他引:3
中国养猪业有着悠久的历史,早在距今约9000-6000年前,中国先民们即已驯养了当地的野猪,中国古代人民十分重视猪种的选育工作,因而中国猪种的优良种性,早在汉代就驰名海内外了。汉代华南小耳猪被大泰国(罗马帝国)所引入,遂育成了古代罗马猪(又名拿波利坦猪)。迨至17、18世纪,中国猪(广东猪种)复被英、美等国所引入,对当时各该国猪种的改良,又起了很大的作用。近年以来,一些畜牧业发达的国家,在世界猪种资源日感贪乏的今天,特别重视引进繁殖力高的中国猪以改进西方国家猪种中母猪的生产力,并由此获得了令人瞩目的改良效果。因此,法、英、日、荷等国纷纷进行试验研究,希望能对世界猪种的改良,再度做出重要的贡献。中国猪的优良种性及其相适应的选种、饲养、管理技术,已为各国所瞩目,并且成为世界各国珍视的财富。我们能拥有如此丰富的宝贵遗产,应引以自豪。 相似文献
328.
中国牦牛品种资源的研究进展 总被引:8,自引:0,他引:8
论文通过对大量的资料和论文查阅、分析和总结,以牦牛资源近十几年研究和生产为线索,从牦牛的资源研究现状、生态生理生化、遗传、种间杂交、本品种选育、野牦牛资源及利用、生产性能、营养及饲养管理、产品品质分析和开发利用以及牦牛疾病等研究内容着手,较全面而系统地阐述了我国牦牛科学近十几年的研究进展,并总结了牦牛科研和生产中存在的主要问题,为了解牦牛科学发展及对今后牦牛科研和生产具有一定的参考价值。 相似文献
329.
Summary. How warning colouration first appeared remains a disputed question in evolutionary biology. A density-dependent transition from crypsis to aposematism that occurs during phase change in the desert locust (Schistocerca gregaria) provides insight into the conditions under which acquiring warning colouration is adaptive. When crowded for only a few hours, solitarious locusts cease avoiding each other and actively aggregate. This occurs well before they acquire warning colouration. We show that accompanying this early behavioural gregarisation is a remarkable shift in feeding behaviour, in which solitarious insects switch from being deterred by a toxic plant alkaloid to feeding avidly upon foods containing it. A computer simulation shows how crypsis ceases to be effective as an anti-predator strategy when solitarious locusts are crowded, how chemical defence becomes essential as conspicuousness increases with local density, and how warning colouration becomes advantageous under these conditions. These findings provide empirical evidence for an adaptive route for the change from a cryptic edible phenotype to a brightly coloured toxic one. 相似文献
330.
Summary. Following herbivory, induced responses involving plant secondary metabolites have been reported in a number of tree species.
Although a wide range of plant secondary metabolites appear to operate as constitutive plant defences in trees belonging to
the Eucalyptus genus, no induced responses have as yet been reported following foliar-chewing insect damage. We empirically tested whether
branch defoliation (artificial and larval) of 2-year-old Eucalyptus globulus Labill. trees altered the abundance of specific plant secondary metabolites immediately (3 months after initial larval feeding)
and 8 months after the cessation of larval feeding. Metabolites assayed, included essential oils, polyphenolic groups and
foliar wax compounds and in all cases their abundance was not significantly altered by defoliation. However, the level of
foliar tannins after 3 months of larval feeding did display a trend that suggested elevated levels as the result of defoliation,
though this trend was not evident 8 months later, indicating that, if real, the response was a rapid and not a delayed induced
response. The level of foliar tannins was also negatively correlated to both average larval survival and average percentage
branch defoliation, suggesting that foliar tannins may operate as toxins and/or anti-feedants to M. privata larval feeding. 相似文献