Dispersal, landscape occupancy and population structure in the butterfly Melanargia galathea

Dispersal is a key ecological process linking metapopulation dynamics in the landscape to distribution patterns at larger spatial scales. In this study, we investigated the landscape occupancy and genetic population structure of a butterfly species, Melanargia galathea. Several landscapes differing in composition and structure were sampled as well as populations at different spatial scales. We found that M. galathea occupied 91.3% of all habitat patches available within a particular landscape, probably due to a dominance of landscape scale processes such as rescue effect and recolonisation. A high level of genetic polymorphism within the sampled populations and a very low amount of genetic differentiation between populations was observed (G_st=0.034), characteristic of species with high dispersal capacity and/or high density. High dispersal rates ensured considerable gene mixing at the landscape scale while the influence of distance on dispersal success was detected at the regional and continental scales by a significant amount of isolation by distance. We also found that, at the landscape scale, the dispersal of this butterfly species was influenced by the spatial distribution of its habitat patches.

Zusammenfassung

Die Ausbreitung ist ein ökologischer Schlüsselprozess, der die Metapopulationsdynamik in einer Landschaft mit den Verbreitungsmustern auf einer größeren räumlichen Skala verbindet. In dieser Studie untersuchten wir die Verbreitungsmuster und die genetische Populationsstruktur einer Schmetterlingsart, Melanargia galathea. Es wurden sowohl einige Landschaften beprobt, die sich in der Zusammensetzung und der Struktur unterschieden, als auch Populationen auf verschiedenen räumlichen Skalen. Wir fanden, dass M. galathea 91.3% aller verfügbaren Habitatflecken in einer bestimmten Landschaft besetzte, möglicherweise aufgrund der Dominanz von Landschaftsskalenprozessen wie “Rescue-Effekt” und Rekolonisation. Es wurde ein hoher genetischer Polymorphismuslevel und ein sehr geringer Umfang genetischer Differenzierung innerhalb der beprobten Populationen beobachtet (G_st=0.034), was charakteristisch für Arten mit einer großen Ausbreitungsfähigkeit und/oder hoher Dichte ist. Hohe Ausbreitungsraten sicherten eine beträchtliche Genvermischung auf der Landschaftsskala, während der Einfluss der Entfernung auf den Verbreitungserfolg auf der regionalen und kontinentalen Skala durch einen signifikanten Anteil der Isolation aufgrund von Entfernung festgestellt wurde. Wir fanden auch, dass auf der Landschaftsskala die Ausbreitung dieses Schmetterlings durch die räumliche Verteilung der Habitatflecken beeinflusst wurde.     

Tolerance to habitat fragmentation influences the colonization of new habitat by forest birds

We examined the relationship between the ability of bird species to persist in fragmented forests and their ability to colonize new forest habitat. Using a long-term data set on the colonization of a forest plantation, we tested the hypothesis that bird species tolerant to habitat fragmentation would detect and colonize the new habitat faster than intolerant species. The forest plantation under study is situated on an area of land reclaimed from the sea (a polder) in the central part of The Netherlands. We constructed an index of tolerance to habitat fragmentation and included it as a predictor variable in a set of three logistic regression models that compared the probability of colonization over four consecutive time periods. After controlling statistically for the effects of regional incidence, preferred habitat and life-history characteristics, there was a significant effect of tolerance to fragmentation on the ability of species to colonize the plantation, and a marginal effect on the timing of colonization. We then examined the effect of the same index of tolerance to fragmentation on colonization patterns over a larger spatial scale. Multivariate regression models showed that the proportion of three polders of different ages occupied by forest bird species was dependent upon the regional incidence of a species, its preferred habitat and its tolerance to fragmentation. The results support the hypothesis that species tolerant to habitat fragmentation detect and colonize new habitat faster than those intolerant to habitat fragmentation.     

黄河三角洲景观组分判定与景观破碎化分析

以地理信息系统（ＡＲＣ／ＩＮＦＯ）为手段,利用遥感卫星图片（ＴＭ５）及其他相关图件,以地貌、土壤与植被作为景观分类指标,把黄河三角洲的景观分成８大类型,３０个景观类型．在此基础上,以斑块的周长面积比值、相对面积及与其他景观类型之间的空间相关关系作为识别基质的指标,判定黄河三角洲景观的基质是柽柳芦苇潮盐土斜平地景观;根据斑块的周长面积比值识别廊道,并进行定量化研究．采用斑块密度对黄河三角洲景观的破碎化进行分析,发现生态交错带内斑块密度大;老河道附近景观破碎化严重     

基于遥感数据源的景观分析系统的设计与实现

在Ｖｉｓｕａｌ Ｃ＋＋环境下,设计并实现了一个景观分析系统。该系统采用提取斑块边界象素集的方法,提高了斑块搜索的速度,而且提供了斑块间距离计算、相邻斑块间边界长度计算等景观分析功能。该系统被应用到北京西北郊同分析中。通过分析表明,该系统不仅能计算面积、周长、中心坐标和最近同类型斑块的距离等单个斑块指数,而且能在此基础上计算景观类型和整个景观层次上的各种指数,从而弥补了目前多数地理信息系统在分析应用     

Vegetation responses to landscape structure at multiple scales across a Northern Wisconsin,USA, pine barrens landscape

Increasing awareness of the importance of scale and landscape structure to landscape processes and concern about loss of biodiversity has resulted in efforts to understand patterns of biodiversity across multiple scales. We examined plant species distributions and their relationships to landscape structure at varying spatial scales across a pine barrens landscape in northern Wisconsin, U.S.A. We recorded plant species cover in 1×1 m plots every 5 m along a 3575 m transect, along with variables describing macro- and micro-landscape structure. A total of 139 understory plant species were recorded. The distributions of many species appeared to be strongly associated with landscape structural features, such as distinct management patches and roads. TWINSPAN and detrended correspondence analysis (DCA) identified three groups of species that overlapped extensively in the ordination, possibly reflecting the relatively homogeneous nature of disturbance in the pine barrens landscape. Distribution of understory plants did not reflect all of the patch types we identified along the transect; plot ordination and classification resulted in three to five plot groups that differed in niche breadth. Wavelet transforms showed varying relationships between landscape features and plant diversity indices (Shannon–Weiner, Simpson's Dominance) at different resolutions. Wavelet variances indicated that patterns of Shannon diversity were dominated by coarse resolutions ranging from 900–1500 m, which may have been related to topography. Patterns of Simpson's Dominance were dominated by 700 m resolution, possibly associated with canopy cover. However, a strong correspondence between overstory patch type and diversity was found for several patch types at ranges of scales that varied by patch type. Effects of linear features such as roads were apparent in the wavelet transforms at resolutions of about 5–1000 m, suggesting roads may have an important impact on plant diversity at landscape scales. At broad scales, landscape context appeared more important to diversity than individual patches, suggesting that changes in structure at fine resolutions could alter overall diversity characteristics of the landscape. Therefore, a hierarchical perspective is necessary to recognize potential large-scale change resulting from small-scale activities.     

景观健康概念、特征及其评价

景观健康是近年来出现景观生态学与新兴的生态系统健康学领域的一个新的生态学概念,旨在探讨人类强烈活动干扰下遭受严重污染与退化,甚至会逐渐消失的景观生态系统的健康问题。本文针对目前所存在的有关景观健康的基本概念,景观健康的特征与标准进行了详细介绍,并就景观健康评价指标的确立,评价时空尺度与等级以及评价方法分别进行了探讨。最后,还强调了在进行景观健康评价时应运用比较的,综合的以及发展的观点开展研究。     

The influences of habitat, landscape structure and climate on local distribution patterns of the nuthatch (Sitta europaea L.)

The nuthatch, Sitta europaea L., is a small (23 g), cavity-nesting woodland bird which, since the 1970s, has been expanding its range in Britain. However, within this range, the species is notably scarce in an area of eastern England. This gap in the species distribution could arise for several reasons including habitat quality, local landscape structure, regional landscape structure and climate. Field surveys and logistic models of breeding nuthatch presence/absence were used to investigate the relative influences of habitat quality, landscape structure and climate on the prevalence of nuthatches in eastern England. Field surveys of woods in the study area indicated that habitat quality was sufficient to support a nuthatch population. A model of habitat occupancy in relation to local landscape structure, developed in the Netherlands, was applied to the study area. The number of breeding pairs predicted for the study area by the model was lower than expected from habitat area alone, suggesting an additional effect of isolation. However, observed numbers were even lower than those predicted by the model. To evaluate the possible roles of climate and large-scale landscape structure on distribution, presence/absence data of breeding nuthatches at the 10-km grid square scale were related to variables describing climate and the amount and dispersion of broadleaved woodland. While climate in the study area appeared suitable, models including landscape variables suggested that the study area as a whole was unlikely to support nuthatches. Although suitable habitat was available, woodland in the study area appeared to be too isolated from surrounding nuthatch populations for colonisation to be successful. This situation may change if current increases in both national and regional populations continue, thus increasing the number of potential colonists reaching the study area. Received: 3 November 1997 / 22 January 1998     

The effect of an agro-pasture landscape on diversity and migration patterns of frugivorous butterflies in Chiapas, Mexico

Few relevant data are available to analyze how landscape structure and composition affect the abundance and movement patterns of tropical insects. Using mark-release recapture experiments we examine the effect of an agro-pasture matrix on changes in diversity and migration of frugivorous butterflies in a tropical fragmented landscape in southern Mexico. In total, 53 frugivorous butterfly species were recorded in the entire landscape. Butterfly species composition was much more similar between sites than plant composition. A total of 3,501 individuals belonging to 41 butterfly species were captured, out of which 23 species (56%) were recaptured at least once. A large fraction of individuals was recaptured at the site of release (91%). We failed to find a significant relationship between the proportion occupied by the matrix and rates of residence, emigration, and immigration. Our results suggest that matrix quality in this and other traditionally managed agro-pasture landscapes plays a key role in both keeping important levels of biodiversity and maintaining constant movements of butterflies between otherwise isolated habitat patches.     

沈阳西郊景观格局变化的研究

景观格局变化的主要原因在于外界的干扰作用,其显著变化具有3种典型类型。本文对景观格局的研究,采用了几种计测指标:(1)各类嵌块体的数目和面积大小;(2)嵌块体的转移矩阵;(3)嵌块体的优势度指数;(4)景观的多样性指数。研究结果表明,沈阳西部景观在经历了30年的变化后,变得更加破碎,出现了较多的块状和岛状嵌块体。景观基质发生了改变,城市化现象较为明显,土地利用的经济效益也有所提高。但由于人口的剧增,人均土地面积在不断减少,荒地开发殆尽,这预示着土地承载能力的饱和与危机的开端。     

武钢厂区景观结构与绿地空间布局研究

应用景观生态学原理对武钢厂区景观结构及结地景观的空间布局进行了调查分析,结果表明,构成武钢厂区景观结构的主体是以建筑铺装玻璃块,工业预留地斑块,公路和铁路廊道组成的人工景观要求,其面积占景观总面积的74．37％,班块优势率达57．70％,其中,建筑铺装斑块面积比率最高（56．43％）,优势度最大（35．59％）,专用绿地斑块破碎化指数高（5．0591ind.hm^-2),分布范围广,道路廊道密度大（13．7772km.km^-2),且公路比铁路对景观的影响更大,既体现了工业区景观结构的基本特征,也反映了武钢厂区趋于合理的景观格局,在绿地景观中,道路绿带斑块数目多,面积比率高（66．07％）,优势度最大（75．31％）,以乔木树种为主体的防护林斑块平均面积大（8454．45m2),环境效益高,观赏绿地斑块植物种类丰富,景观效果好,以道路绿带为骨架,成片防护林和观赏绿地为中心,将各分厂绿地接成四大绿化区域的武钢厂区绿地系统已初步形成,但厂区荒草地斑块优势度偏高,防护林面积较小,道路绿带仍不完整,应进一步重视厂区废弃地开发和绿地系统建设。     

Stabilizing effects in spatial parasitoid-host and predator-prey models: a review

We review the literature on spatial host-parasitoid and predator-prey models. Dispersal on its own is not stabilizing and can destabilize a stable local equilibrium. We identify three mechanisms whereby limited dispersal of hosts and parasitoids combined with other features, such as spatial and temporal heterogeneity, can promote increased persistence and stability. The first mechanisms, "statistical stabilization", is simply the statistical effect that summing a number of out-of-phase population trajectories results in a relatively constant total population density. The second mechanism involves decoupling of immigration from local density, such that limited dispersal between asynchronous patches results in an effect that mimics density-dependence at the local patch level. The third mechanism involves altering spatially averaged parameter values resulting from spatial heterogeneity in density combined with non-linear responses to density. Persistence in spatially explicit models with local dispersal frequently associated with self-organized spatial patterning.     

景观指数分类、应用及构建研究

在景观生态学研究中,理解与把握景观格局变化的生态学原则至关重要,用景观指数描述景观格局及变化,建立格局与景观过程之间的联系,是景观生态学最常用的定量化研究方法,本文在综合前人对景观指数的基础上,对景观指数研究从景观指数的分类研究,指数对景观格局的描述研究,指数之间的相关性研究及指数构建研究等4方面进行了总结,并从单个景观指数与指数体系两个层次上提出了判定景观指数优劣及景观指数应用的一般性原则。     

Impact of landscape and corridor design on primates in a large-scale industrial tropical plantation landscape

Tropical plantations are rapidly expanding as a source of industrial wood. In Indonesia, such large-scale industrial plantations are generally made of large mono-specific blocks interspersed with natural forest remnants. The extent and biodiversity value of these remnants vary as laws and regulations on their design and management are either unclear, without solid scientific basis or left to the interpretation of private companies responsible for the plantations. Our study area comprises of three Acacia mangium plantations, which have on average 18% of their total area set aside from production and conserved as natural forests. These remnant natural forests may, if appropriately designed and managed, be used to mitigate the negative impact of plantations on biodiversity by providing some degree of connectivity with and between remaining natural forest patches (such as the Tesso Nilo conservation area). We sampled natural vegetation in one and primate diversity in all three plantation sector and examined patterns of primate species richness and abundance with relation to spatial arrangement and dimensions of conservation area, which has been set aside from plantation production. We demonstrate unambiguously the critical importance of a well-connected network of natural forest corridors in the plantation landscape to maintain primates and discuss the potential biodiversity value of natural forest remnants in broad-scale industrial landscapes.     

辽河三角洲湿地的景观破碎化分析

利用遥感、ＧＩＳ手段对辽河三角洲的湿地景观进行研究,并选用６种不同的方法对研究区的景观破碎化程度进行分析．结果表明,研究区的景观破碎化程度较低,总体斑块密度为０．２８６个·ｋｍ－２,廊道密度为１．０９８ｋｍ·ｋｍ－２,聚集度指数为０．９５５．景观破碎化与人类活动密切相关,随着人类活动的增加,景观破碎化程度加深．廊道景观的发展是景观破碎化的前提与动因．     

Invertebrate dispersal and habitat heterogeneity: Expression of biological traits in a seagrass landscape

Seagrass meadows harbour diverse faunal assemblages, but the relative importance of landscapes attributes, settlement processes and biological traits of individual species for recruitment patterns is poorly understood. To quantify the influence of habitat heterogeneity on larval, juvenile and adult post-larval dispersal, invertebrates (> 125 µm) were collected in benthic settlement traps at five occasions (June-August) in three habitats; continuous seagrass, seagrass patches and bare sand. The study was carried out by SCUBA diving in a subtidal (2.5 m depth) seagrass landscape dominated by Zostera marina L. in the Baltic Sea. Traps collected totally > 30 taxa, with non-significant effects of habitat on species richness and total abundance. Total number of invertebrates exhibited strong temporal variability, probably driven by wind-induced bedload and water column transport. Surprisingly, traps located in small (< 12 m²) patches contained on average almost twice as many individuals as traps located in the continuous vegetation. Dominating taxa such as nematodes, copepods, and oligochaetes were found in similar densities across the landscape. In contrast, location within the landscape had strong effects on bivalve settlement and redistribution patterns, resulting in significantly lower densities in continuous vegetation compared to patches and bare sand. A biological trait analysis indicated that semi-mobile taxa with annual protracted direct development, and short-distance dispersal are probably of higher importance for the community assembly process in this environment than long-distance larval dispersal. Results suggest that seagrass landscapes are highly dynamic environments, characterized by time and species-specific effects of landscape attributes on animal dispersal and recruitment. A conceptual model illustrating interactions between settling larvae and landscape heterogeneity is presented.     

Gypsy moth response to landscape structure differs from neutral model predictions: implications for invasion monitoring

Simulations of dispersal across computer-generated neutral landscapes have generated testable predictions about the relationship between dispersal success and landscape structure. Models predict a threshold response in dispersal success with increasing habitat fragmentation. A threshold is defined as an abrupt, disproportionate decline in dispersal success at a certain proportion of habitat in the landscape. To identify potential empirical threshold responses in invasion success to landscape structure, we quantified the relationship between progression of the gypsy moth (Lymantria dispar) invasion wavefront across Michigan (1985–1996) and the structure of the Michigan landscape using two indices of invasion success and six landscape metrics. We also examined the effect of scale of analysis and choice of land cover characterization on our results by repeating our analysis at three scales using two different land cover maps. Contrary to simulation model predictions, thresholds in invasion success did not correspond closely with thresholds in landscape structure metrics. Increased variation in invasion success indices at smaller scales of analysis also suggested that invasion success should be studied at larger spatial extents (≥75 km²) than would be appropriate for characterizing individual dispersal events. The predictions of individual dispersal models across neutral landscapes may have limited applications for the monitoring and management of vagile species with excellent dispersal capabilities such as the gypsy moth.     

Resource concentration hypothesis: effect of host plant patch size on density of herbivorous insects

The resource concentration hypothesis (Root 1973) predicts that specialist herbivorous insects should be more abundant in large patches of host plants, because the insects are more likely to find and stay longer in those patches. Between August 1989 and January 1990 we experimentally tested Root's hypothesis by analyzing the numerical response of four species of herbivorous insects associated with patches of 4, 16, 64 and 225 cabbage plants, Brassica oleracea var. capitata. In addition, we studied the colonization of patches by adults of Plutella xylostella (L.) (Lepidoptera: Plutellidae), and the migration of their larvae in patches of different sizes. No herbivorous insect densities differed significantly with patch size. Adults of P. xylostella colonized all kind of patches equally. Larvae did not migrate between patches, and their disappearance rate did not differ between patches. The resource concentration hypothesis is organism-dependent, being a function of the adult and juvenile herbivore dispersal behavior in relation to the spatial scale of patchiness.     

景观分类与评价的生态原则

在分析景观定义的基础上 ,概述了景观分类的生态学原则 ,提出了自然、经营和人工等不同景观类型的特性和研究重点 ,并对景观的独特性、多样性、功效性、宜人性及美学价值的评价进行了探讨 .文章还介绍了景观保护的概念和实践