荒漠破碎化生境中长爪沙鼠集合种群野外验证研究

近年来,人类活动和自然干扰,导致内蒙古阿拉善荒漠区生境的破碎化,出现了长爪沙鼠在不同斑块间的不连续分布,每一斑块内可能存在一个局域种群,而集合种群建立的前提条件,是局域种群斑块状分布在离散的栖息地环境中。2002~2012年每年的4~10月,在阿拉善荒漠区禁牧、轮牧、过牧和开垦4种人为不同利用方式形成的生境斑块中,采用标志重捕法对长爪沙鼠（Meriones unguiculatus）种群进行定点监测。通过分析长爪沙鼠种群动态,计算各局域种群的灭绝风险,利用Spearman秩相关系数检验种群动态的空间同步性,同时以种群周转率对长爪沙鼠扩散能力进行评估,以检验阿拉善荒漠区长爪沙鼠种群空间结构是否具有经典集合种群的功能。结果表明：（1） 不同生境斑块可被长爪沙鼠局域种群占据,11年间捕获长爪沙鼠2~7次不等;（2） 长爪沙鼠所有局域种群均具有灭绝风险,在轮牧区和禁牧区灭绝率高达1.000 0,开垦区灭绝率最低,也达到0.333 4,而本研究期间最大局域种群（2008年过牧区,26只/hm²）,在2010年发生了局域灭绝;（3） 不同生境斑块间没有明显的空间隔离而阻碍局域种群的重新建立,长爪沙鼠扩散能力较强,绝大部分月份的种群周转率在50.0%以上,特别是周转率达到100.0%的月份较多;（4） 不同生境斑块间仅轮牧区和禁牧区中长爪沙鼠种群密度显著正相关（P<0.05）,而其他生境斑块间相关性均不显著（P >0.05）,长爪沙鼠局域种群整体显示出明显的非同步空间动态。阿拉善荒漠区长爪沙鼠种群满足作为经典集合种群物种区域续存的4个条件,具有作为研究小哺乳动物集合种群的潜在价值。     

Voles on small islands: effects of food limitation and alien predation

Ecosystems of three trophic levels may be bottom-up (by food-plant availability) and/or top-down (by predators) limited. Top-down control might be of greater consequence when the predation impact comes from an alien predator. We conducted a replicated two-factor experiment with field voles (Microtus agrestis) during 2004-2005 on small islands of the outer archipelago of the Baltic Sea, south-west Finland, manipulating both predation impact by introduced American mink (Mustela vison) and winter food supply. In autumn 2004, we live-trapped voles on five islands from which mink had been consistently removed, and on four islands where mink were present, and provided half of these islands with 1.8 kg oats per vole. Body mass of female voles increased as a response to supplementary food, whereas both food supplementation and mink removal increased the body mass of male voles in subsequent spring. During winter, there was a positive effect of supplementary food, but in the subsequent summer, possible positive long-term impacts of food supplementation on field voles were not detected. Mink removal appeared not to affect density estimates of field voles during the winter and summer immediately after food addition. Trapping data from 2004 to 2005 and 2007 suggested, however, that in two out of three summers densities of voles were significantly higher in the absence than in the presence of mink. We conclude that vole populations on small islands in the archipelago of the Baltic Sea are mainly bottom-up limited during winter (outside the growing season of food plants), when food availability is low, and limited by mink predation during summer which slows population growth during the reproductive season of voles.     

Invasive species management in two-patch environments: agricultural damage control in the raccoon (<Emphasis Type="Italic">Procyon lotor</Emphasis>) problem,Hokkaido, Japan

We develop discrete-time models for analyzing the long-run equilibrium outcomes on invasive species management in two-patch environments with migration. In particular, the focus is on a situation where removal operations for invasive species are implemented only in one patch (controlled patch). The new features of the model are that (1) asymmetry in density-dependent migration is considered, which may originate from impact of harvesting as well as heterogeneous habitat conditions, and (2) the effect of density-dependent catchability accounts for the fact that the required effort level to remove one individual may rise as the existing population decreases. The model is applied to agricultural damage control in the raccoon (Procyon lotor) problem that has occurred in Hokkaido, Japan. Numerical illustrations demonstrate that the long-run equilibrium outcomes largely depend on the degree of asymmetry in migration as well as the sensitivity of catchability in response to a change in the population size of the invasive species. Furthermore, we characterize the conditions under which the economically optimal effort levels are qualitatively affected by the above two factors, and conclude that aiming at local extermination of invasive species in the controlled patch is justified. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Vector borne diseases on an urban environment: The effects of heterogeneity and human circulation

We study the effect of human circulation and host/vector heterogeneities on the onset of epidemics of arboviruses. From a meta-population dynamics based on the classical Bailey–Dietz model, we derive a multi-group model under three assumptions: (i) fast host sojourn time-scale; (ii) mosquitoes do not move; (iii) time homogeneity and strong connectivity of human circulation. Within this modelling framework, three different kinds of R₀ appear: (i) the “true” or “global” R₀—derived from the corresponding next generation matrix; (ii) the uniform R₀—obtained if the patches are taken homogeneous; (iii) the local R₀s—obtained if the patches are disconnected. We show that there is relevant epidemiological information associated to all of them. In particular, they can be used to understand the effects of changing the circulation on the value of the global R₀. We also present additional results on the effects on R₀ of different vector control policies, and a simulation with data from the city of Rio de Janeiro, Brazil.     

Genetic diversity patterns in Phragmites australis at the population,regional and continental scales

Genetic diversity, population structure and interrelationships were investigated in eight populations of the common reed, Phragmites australis, in the Po Plain, Italy, by means of amplified fragments length polymorphisms (AFLPs) and random amplified polymorphic DNAs (RAPDs). Patterns of genetic diversity were analysed in relation to size, age and degree of human impact in the wetlands and compared with that of a distant population in Romania. Genetic distances between Po Plain clones and geographically distant clones were measured to determine the geographical extent of the gene pool.     

不同干扰下荒漠啮齿动物种群动态的空间同步性

荒漠啮齿动物是动物生态学研究中的重要类群,对于丰富种群和群落生态学理论具有重要意义.国外关于荒漠啮齿动物的研究较多,尤以北美的研究较为深入,涉及群落组成(Brown,1973)、生态位(Harris, 1984;Kenagy and Bartholomew, 1985)、物种共存(Brown and Munger,1985)、资源分享及微生境选择(Brown and Lieberman,1973;Price,1978)等方面;而国内关于荒漠啮齿动物研究相对较少.     

Viability of meta-populations of wetland birds in a fragmented landscape: testing the key-patch approach

The key patch approach assumes that metapopulations in fragmented landscapes are likely to be viable with at least one “key” sub-population that is sufficiently large to ensure re-colonization of surrounding minor habitat patches. It is based on a minimum viable number of breeding pairs and within-breeding season dispersal distance, linked to size of the animal and longevity. It was tested using census data of 15 wetland bird species (bearded tit, bluethroat, great reed warbler, sedge warbler, Savi’s warbler, grasshopper warbler, spotted crake, water rail, common snipe, common teal, garganey, little bittern, night heron, great bittern and marsh harrier) in 14 wetland complexes of variable size (3–55 km²) spread across the Netherlands (distances ranging 4–156 km). First, for each species it was assessed whether a wetland harbored a key subpopulation, which was the case for the sedge warbler (7 key subpopulations), grass-hopper warbler (2), water rail (2), bearded tit, bluethroat, Savi’s warbler, common teal, garganey, great bittern and marsh harrier (all one key subpopulation).Together with the adjacent sub-populations present within breeding season dispersal distance, 10 out of the 15 studied species formed viable meta-populations. This was compared with the trend in the census data of 13 species for 1990–2000 and was found to correspond significantly (likelihood ratio test, P = 0.003): species without a viable meta-population had declined (2 out of 4) or remained stable (2 out of 4), whereas viable meta-populations had increased (6 out of 9) or remained comparatively stable (2 out of 9). One wetland complex, the Oostvaardersplassen, stood out in that it haboured key sub-populations for 9 out of the 15 species studied. Variation in quantity of specific habitat (area or perimeter marshland, woodland or open water) in a wetland complex was of limited importance explaining abundance patterns, since all covaried strongly with total area among the wetland complexes, with the exception of water perimeter. Apparently, these wetlands on peat harbour largely similar landscapes. Indeed, population sizes of most birds covaried strongly and in a PCA two distinct clusters of species were identified that shared high numbers of breeding pairs in the same, larger, wetland complexes, the first (3 species) including the great reed warbler, and the second (9 species) the water rail.