景观生态学:两栖动物生态学研究的新途径

全球两栖动物正以远超过自然灭绝的高速率灭绝,这与生境丧失和景观破碎化有着直接关系。生境丧失导致两栖动物的生存空间减少,使局部种群消失,而景观破碎化则导致两栖动物种群之间的隔离度增加,不利于动物的繁殖和扩散。但两者往往是同时出现,相互作用。复合种群、景观连接度、景观遗传学及景观模型模拟等理论和方法的发展,为在生境丧失与破碎化景观下两栖动物的种群结构、组成和动态变化研究提供了理论基础和技术方法。同时景观生态学中特别重视研究的尺度,生境破碎化是发生在景观尺度下的生境变化过程,因此对生境破碎化的影响应该从现有的主要集中在斑块尺度和斑块-景观尺度转变到景观尺度上来。     

生境破碎化对植物-昆虫及昆虫之间相互关系的影响

生境破碎化对生物多样性和生态系统功能影响是当前国内外生态学家研究的热点问题之一。文章针对生境破碎化的内涵、量度指标进行介绍,着重分析生境破碎化对植物-昆虫关系的影响,包括植物与植食性昆虫的关系、植物与传粉昆虫的关系、种子与种子捕食者的关系,植物及其分解者的关系,还分析生境破碎化对昆虫-昆虫关系的影响,包括昆虫及其拟寄生物的关系、捕食者与猎物的关系。通过对上述方面的阐述,旨在更好地理解生境破碎化对动植物群落相互关系产生的深刻影响,并提出今后研究中应注意的问题和研究热点。     

Spatial structure of avifauna along urban-rural gradients

We examined the pattern of species composition of breeding birds along urban-rural gradients in the Osaka Prefecture, western Japan. We recorded the proportion of nine types of land-use and the presence/absence of each of 76 breeding birds in 5 km square quadrats on a map of the Prefecture. The proportion of woodland and farmland which increased from urban to rural areas were two major enviornmental gradients according to Principal Component Analysis of the nine types of land-use. Ordination by Canonical Correspondence Analysis (CCA) showed that the breeding bird distribution differentiated along the two major clines, woodland and farmland. The avifauna changed successively along these environmental gradients. There were no discrete boundaries of the distribution of bird species groups. We tentatively classified five groups of quadrats on the ordination plane of the sample score. The geographic position of these five groups on a map preserved the environmental gradient, but showed that water (seashore and river) was a stronger influence on bird species composition than land-use pattern. Although the diversity of land-use seemed to raise species richness in the third group, the less diverse, woodland-rich group contained as many species as the third group. Four groups of bird species, and one group in which species occurred in more than 90% of the quadrats, were classified in the CCA-ordination plane. The occurrence of these bird groups correlated with land-use; the first group with woodland area, the second with scatter woodland, the third with farmland and the fourth with seashore.     

黑龙江省完达山地区马鹿生境破碎化及其影响因子

应用景观生态学原理和地理信息系统技术,分析黑龙江省完达山地区马鹿生境相关因子重要性、对景观连接度进行模糊相对赋值,建立了景观连接度评价模型及景观斑块指数,研究了黑龙江省完达山地区关于马鹿生境的景观连接度水平、生境的适宜性以及景观的空间结构。结果表明:(1)在155.6km2的面积中,适宜地区的总面积仅为14.81km2,占研究地区的9.52%;次适宜地区的总面积为9.57km2,占研究地区的6.15%;一般适宜地区的总面积为130.05km2,占研究地区的83.58%;不适宜地区的总面积为1.17km2,占研究地区的0.75%;(2)研究地区马鹿各类适宜地区呈多个斑块且相互隔离,在空间分布上处于破碎状态,而且不适宜地区斑块(人为活动景观)的面积比例虽小,在生态系统中形态上的破碎化程度较小,但对马鹿的生境的生态功能的丧失起到重要作用。     

Modelling the effect of habitat fragmentation on range expansion in a butterfly

There is an increasing need for conservation programmes to make quantitative predictions of biodiversity responses to changed environments. Such predictions will be particularly important to promote species recovery in fragmented landscapes, and to understand and facilitate distribution responses to climate change. Here, we model expansion rates of a test species (a rare butterfly, Hesperia comma) in five landscapes over 18 years (generations), using a metapopulation model (the incidence function model). Expansion rates increased with the area, quality and proximity of habitat patches available for colonization, with predicted expansion rates closely matching observed rates in test landscapes. Habitat fragmentation constrained expansion, but in a predictable way, suggesting that it will prove feasible both to understand variation in expansion rates and to develop conservation programmes to increase rates of range expansion in such species.     

Composition of an avian guild in spatially structured habitats supports a competition-colonization trade-off

Assuming better colonization abilities of inferior competitors, the competition-colonization trade-off (CCTO) is one of the hypotheses that explains spatial variation of species composition in fragmented habitats. Whereas this mechanism may structure some plant and insect communities, ecologists have failed to document its operation in other natural systems, and its generality has been questioned. We combined fieldwork and published data to study the composition of a guild of passerines (Parus cristatus, Parus montanus, Parus ater and Regulus regulus) inhabiting 10 landscapes that differed in the amount of forest habitat. The species were ordered in a stable, well-defined competitive hierarchy, and the dispersal ability of each species was inversely correlated with its position in this hierarchy. In functionally continuous landscapes, superior competitors occupied most fragments and all guild members commonly occurred. The relative incidences of superior and inferior competitors were reversed, and differences amplified, in landscapes where patches were physically (distance) or functionally (matrix hardness) isolated. We found little support for two competing hypotheses, namely reduced habitat quality in isolated patches and lower abundance of a keystone predator (Glaucidium passerinum) in fragmented landscapes. We concluded that the CCTO offered the most probable explanation for variation in the composition of the Parus guild across landscapes.