用空间直观模型是否足以从斑块占据性资料中推断集合种群的动态过程?

在集合种群的研究中,经常要根据空间占据性数据应用斑块模型来推断种群的动态过程,在保护生物学应用中,斑块占据性模型的参数估测对于阐释集合种群动态和预测种群对生境破坏的反应极为重要。我们探讨了一种广泛应用的空间直观模型——率函数模型(Incidence function model)中参数估测的不确定性问题,通过构建由50个斑块组成的网络和两个假想的已知参数的集合种群,应用模拟模型产生集合种群随时间变化的斑块占据性数据系列：即快照(snapshot)。然后,根据这些快照,应用率函数模型和最大似然法估测种群动态参数。此外,我们还给出了传统的率函数模型的一个变形,这个变形包含了目标区效应(Target area effect)：即一个斑块的占据概率不但取决于空间隔离度,也取决于斑块本身面积的大小。结果表明：根据同一个集合种群不同的快照所估测的参数可以有很大差异,一个快照得出的参数提示的是占据性强但存活率低的集合种群,而另一个快照可能反映的是一个占据性弱但存活率高的集合种群。应用传统的率函数模型于一个包含了目标区效应的集合种群,导致斑块大小相关的灭绝率参数估测的正偏差。因此,仅根据一个快照的空间占据性数据来推测集合种群的过程有很大的不确定性[动物学报49(6)：787～794,2003]。     

Reconciling theoretical approaches to stochastic patch-occupancy metapopulation models

There appear to be two different kinds of theoretical results about stochastic patch-occupancy metapopulation models: those recently proposed by Gyllenberg and Silvestrov about metapopulations including a very stable patch, and those by Darroch and Seneta about more general metapopulations. Based on the spectral theory of linear operators, it is shown that the results by Gyllenberg and Silvestrov are a limiting case of those by Darroch and Seneta. Taking the examples proposed by Gyllenberg and Silvestrov as a case study, the application and relevance of these results are discussed, with a particular stress to their bearing on real metapopulations.     

Metapopulation dynamics: Does it help to have more of the same?

With the interest in conservation biology shifting towards processes from patterns, and to populations from communities, the theory of metapopulation dynamics is replacing the equilibrium theory of island biogeography as the population ecology paradigm in conservation biology. The simplest models of metapopulation dynamics make predictions about the effects of habitat fragmentation - size and isolation of habitat patches - on metapopulation persistence. The simple models may be enriched by considerations of the effects of demographic and environmental stochasticity on the size and extinction probability of local populations. Environmental stochasticity affects populations at two levels: it makes local extinctions more probable, and it also decreases metapopulation persistence time by increasing the correlation of extinction events across populations. Some controversy has arisen over the significance of correlated extinctions, and how they may affect the optimal subdivision of metapopulations to maximize their persistence time.     

Combining larval habitat quality and metapopulation structure – the key for successful management of pre-alpine Euphydryas aurinia colonies

This study aims to analyse larval habitat preferences and landscape level population structure of the threatened Marsh Fritillary butterfly, Euphydryas aurinia, and discusses implications for the conservation and management of this strongly declining species in central Europe. Whereas current management strategies are mainly based on studies of habitat requirements of adult individuals, we intend to emphasise larval habitat quality and population processes at the landscape level as additional key factors. Microhabitat preference analysis of egg-laying females showed that eggs were predominantly laid on prominent large-sized host plant individuals. Additionally, when Succisa pratensis was used as a host plant (as opposed to Gentiana asclepiadea), host individuals in open vegetation structure were preferred. Optimal oviposition conditions were present in recently abandoned calcareous fen meadows and at the edges of such meadows currently in use. A two-year patch-occupancy study in the northern pre-alpine region of south-west Germany indicated that E. aurinia lives in a metapopulation. In a logistic-regression model, patch size, isolation, and habitat quality explained 82% of the observed patch-occupancy pattern in 2001. Our data suggest that a suitable conservation strategy must incorporate both the conservation of a network of suitable habitat patches, and efforts to maximise local habitat quality by ensuring that host plants can grow to a large size and are surrounded by sparse and low vegetation cover.     

The Impact of the Allee Effect in Dispersal and Patch-Occupancy Age on the Dynamics of Metapopulations

In this paper, we introduce a Levins-type metapopulation model with empty and occupied patches, and dispersing population. We structure the proportion of occupied patches according to the patch-occupancy age. We observe that patch-occupancy age may destabilize the metapopulation, leading to persistent oscillations. We also allow for the dispersal rate to vary with the proportion of empty patches in a monotone or unimodal way. The unimodal dependence leads to multiple non-trivial equilibria and bistability when the reproduction number of the metapopulation < 1 but greater than a lower critical value ^*. We show that the metapopulation will persist independently of its initial status if > 1.     

Spatially structured metapopulation models: global and local assessment of metapopulation capacity

We model metapopulation dynamics in finite networks of discrete habitat patches with given areas and spatial locations. We define and analyze two simple and ecologically intuitive measures of the capacity of the habitat patch network to support a viable metapopulation. Metapopulation persistence capacity lambda(M) defines the threshold condition for long-term metapopulation persistence as lambda(M)>delta, where delta is defined by the extinction and colonization rate parameters of the focal species. Metapopulation invasion capacity lambda(I) sets the condition for successful invasion of an empty network from one small local population as lambda(I)>delta. The metapopulation capacities lambda(M) and lambda(I) are defined as the leading eigenvalue or a comparable quantity of an appropriate "landscape" matrix. Based on these definitions, we present a classification of a very general class of deterministic, continuous-time and discrete-time metapopulation models. Two specific models are analyzed in greater detail: a spatially realistic version of the continuous-time Levins model and the discrete-time incidence function model with propagule size-dependent colonization rate and a rescue effect. In both models we assume that the extinction rate increases with decreasing patch area and that the colonization rate increases with patch connectivity. In the spatially realistic Levins model, the two types of metapopulation capacities coincide, whereas the incidence function model possesses a strong Allee effect characterized by lambda(I)=0. For these two models, we show that the metapopulation capacities can be considered as simple sums of contributions from individual habitat patches, given by the elements of the leading eigenvector or comparable quantities. We may therefore assess the significance of particular habitat patches, including new patches that might be added to the network, for the metapopulation capacities of the network as a whole. We derive useful approximations for both the threshold conditions and the equilibrium states in the two models. The metapopulation capacities and the measures of the dynamic significance of particular patches can be calculated for real patch networks for applications in metapopulation ecology, landscape ecology, and conservation biology.     

Competition between unit-restricted fungi: a metapopulation model

We aimed to provide a theoretical framework for dynamic studies of competition between fungi living on divided and ephemeral resources. We previously adapted the seminal Skellam's patch-occupancy model (Skellam, 1951) to describe the population dynamics of one species of unit-restricted fungus whose mycelial growth occurs within resource units and which colonizes new resource units by spore dispersal (Gourbiere et al., 1999). In this study, we extended this model to describe the competition between a pair of unit-restricted fungal species that interact with each other inside units by decreasing their spore production. Accordingly, we designed a discrete-time metapopulation model where all patches go extinct at each generation and species interact by lowering their propagule production in jointly occupied patches. We showed that the two species easily coexist although there is no trade-off between their competitive and colonization abilities. Furthermore, the outcome of the competition process can depend on a founder effect. Founder effect determines either which species is excluded or the relative densities of each species when they coexist. We investigated the implications of these results on the distribution and abundance of fungal species along environmental gradients. This work bridges the gap between the mycological theory of "Resource Units" and the metapopulation theory, showing the specificity of fungal exploitation competition. We suggest that unit-restricted fungal species are appropriate biological models to test the theoretical results of the metapopulation theory, such as the appearance of alternative stable equilibria.     

复合种群动态研究进展

复合种群动态研究是当今保护生物学和生态学中最热门的课题之一。在此较为详细地介绍了复合种群动态的有关概念和术语、经验研究和理论探索的最新进展以及相关的预测模型 ,对我国开展相关研究有参考价值。     

Metapopulation models for seasonally migratory animals

Metapopulation models are widely used to study species that occupy patchily distributed habitat, but are rarely applied to migratory species, because of the difficulty of identifying demographically independent subpopulations. Here, we extend metapopulation theory to describe the directed seasonal movement of migratory populations between two sets of habitat patches, breeding and non-breeding, with potentially different colonization and extinction rates between patch types. By extending the classic metapopulation model, we show that migratory metapopulations will persist if the product of the two colonization rates exceeds the product of extinction rates. Further, we develop a spatially realistic migratory metapopulation model and derive a landscape metric-the migratory metapopulation capacity-that determines persistence. This new extension to metapopulation theory introduces an important tool for the management and conservation of migratory species and may also be applicable to model the dynamics of two host-parasite systems.     

Exact asymptotic analysis for metapopulation dynamics on correlated dynamic landscapes

We compute the mean patch occupancy for a stochastic, spatially explicit patch-occupancy metapopulation model on a dynamic, correlated landscape, using a mathematically exact perturbation expansion about a mean-field limit that applies when dispersal range is large. Stochasticity in the metapopulation and landscape dynamics gives negative contributions to patch occupancy, the former being more important at high occupancy and the latter at low occupancy. Positive landscape correlations always benefit the metapopulation, but are only significant when the correlation length is comparable to, or smaller than, the dispersal range. Our analytical results allow us to consider the importance of spatial kernels in all generality. We find that the shape of the landscape correlation function is typically unimportant, and that the variance is overwhelmingly the most important property of the colonisation kernel. However, short-range singularities in either the colonisation kernel or landscape correlations can give rise to qualitatively different behaviour.     

The applicability of metapopulation theory to large mammals

Metapopulation theory has become a common framework in conservation biology and it is sometimes suggested that a metapopulation approach should be used for management of large mammals. However, it has also been suggested that metapopulation theory would not be applicable to species with long generations compared to those with short ones. In this paper, we review how and on what empirical ground metapopulation terminology has been applied to insects, small mammals and large mammals. The review showed that the metapopulation term sometimes was used for population networks which only fulfilled the broadest possible definition of a metapopulation, i.e. they were subpopulations connected by migrating individuals. We argue that the metapopulation concept should be reserved for networks that also show some kind of metapopulation dynamics. Otherwise it applies to almost all populations and loses its substance. We found much empirical support for metapopulation dynamics in both insects and small mammals, but not in large mammals. A possible reason is the methods used to confirm the existence of metapopulation dynamics. For insects and small mammals, the common approach is to study population turnover through patch occupancy data. Such data is difficult to obtain for large mammals, since longer temporal scales need to be covered to record extinctions and colonizations. Still, many populations of large mammals are exposed to habitat fragmentation and the resulting subpopulations sometimes have high risks of extinction. If there is migration between the subpopulations, the metapopulation framework could provide valuable information on their population dynamics. We suggest that a metapopulation approach can be interesting for populations of large mammals, when there are discrete breeding subpopulations and when these subpopulations have different growth rates and demographic fates. Thus, a comparison of the subpopulations’ demographic fates, rather than subpopulation turnover, can be a feasible alternative for studies of metapopulation dynamics in large mammals.     

The contribution of patch topology and demographic parameters to population viability analysis predictions: the case of the European tree frog

Population viability analyses (PVA) are increasingly used in metapopulation conservation plans. Two major types of models are commonly used to assess vulnerability and to rank management options: population-based stochastic simulation models (PSM such as RAMAS or VORTEX) and stochastic patch occupancy models (SPOM). While the first set of models relies on explicit intrapatch dynamics and interpatch dispersal to predict population levels in space and time, the latter is based on spatially explicit metapopulation theory where the probability of patch occupation is predicted given the patch area and isolation (patch topology). We applied both approaches to a European tree frog (Hyla arborea) metapopulation in western Switzerland in order to evaluate the concordances of both models and their applications to conservation. Although some quantitative discrepancies appeared in terms of network occupancy and equilibrium population size, the two approaches were largely concordant regarding the ranking of patch values and sensitivities to parameters, which is encouraging given the differences in the underlying paradigms and input data.     

Dispersal-induced desynchronization: from metapopulations to metacommunities

The conceptualization of fragmented populations in terms of metapopulation theory has become standard over the last three decades. It is well known that increases in between‐patch migration rates cause more synchronous population fluctuations and that this coherence increases the risk of global metapopulation extinction. Because species’ migration rates and the probability of individuals surviving migration events depend on the effective distance between patches, the benefit of improving conservation corridors or the matrix between habitat patches has been questioned. As populations occur in the context of larger communities, moving from a metapopulation to a metacommunity model framework is a natural extension to address the generality of these conclusions. We show how considering a metacommunity can modify the conclusion that decreasing the effective distance between habitat patches (via improving matrix quality or other measures) necessarily increases the degree of metapopulation synchrony. We show that decreases in effective between‐patch distance may deter population synchrony because of the simultaneous effect this change has on the migration patterns of other species. These results indicate that species interactions need to be considered when the effect of conservation measures on population synchrony, and ultimately persistence, is addressed.     

A unifying framework for metapopulation dynamics

Many biologically important processes, such as genetic differentiation, the spread of disease, and population stability, are affected by the (natural or enforced) subdivision of populations into networks of smaller, partly isolated, subunits. Such "metapopulations" can have extremely complex dynamics. We present a new general model that uses only two functions to capture, at the metapopulation scale, the main behavior of metapopulations. We show how complex, structured metapopulation models can be translated into our generalized framework. The metapopulation dynamics arising from some important biological processes are illustrated: the rescue effect, the Allee effect, and what we term the "antirescue effect." The antirescue effect captures instances where high migration rates are deleterious to population persistence, a phenomenon that has been largely ignored in metapopulation conservation theory. Management regimes that ignore a significant antirescue effect will be inadequate and may actually increase extinction risk. Further, consequences of territoriality and conspecific attraction on metapopulation-level dynamics are investigated. The new, simplified framework can incorporate knowledge from epidemiology, genetics, and population biology in a phenomenological way. It opens up new possibilities to identify and analyze the factors that are important for the evolution and persistence of the many spatially subdivided species.     

物种保护的理论基础——从岛屿生物地理学理论到集合种群理论

全球面临着生境破碎化的危机,物种保护已成为人类面临的重大课题,并不是所有的人对岛屿生物地理学理论的产生及其关注的海洋岛屿都很熟悉,但是越来越多生物赖以生存的自然栖息地的丧失和破碎化都是有目共睹的,岛屿生物地理学和集合种群理论是目前物种保护的两个基本理论,物种迁入率和绝灭率的动态变化决策岛屿上的物种丰富度是岛屿生物地理学理论的核心内容,而集合种群理论关注的是局部种群之间个体迁移的动态以及物种的续存条件,在概述两个理论形成、发展及其核心内容的基础上,着重比较它们的异同点以及在生态学理论和实践中的应用,并论述物种保护理论范式从岛屿生物地理学向集合种群理论转变的基本背景和原因。     

Metapopulation persistence in heterogeneous landscapes: lessons about the effect of stochasticity

This article addresses an important aspect of the analysis of metapopulation persistence. It highlights some consequences of ignoring and including stochasticity in the sequence of extinction and colonization events. The results are based on a comparative analysis of the outcomes of two (one deterministic, one stochastic) spatially realistic metapopulation models and a search for common effects and differences. One key result of the article is that, under certain conditions, there are extra effects of the landscape structure (number and configuration of patches, patch size distribution) on metapopulation persistence if stochasticity is included. In these cases, ignoring or including stochasticity can change conclusions about the persistence status but also ranking orders, relative results, and qualitative trends. A list of conditions is provided under which including stochasticity is vital to prevent counterproductive conclusions about metapopulation persistence. The results of the overall study are condensed in five lessons about the effect of stochasticity. A number of implications for ecological theory and conservation management are discussed. The study demonstrates the potential of three recently published approximation formulas (metapopulation capacity lambdaM, mean lifetime Tm, and effective number of patches N) to serve as tools for ecological analysis and thinking.     

Evolution of complex life cycles of amphibians: bridging the gap between metapopulation dynamics and life history evolution

Current evolutionary models for amphibian life cycles reflect tradeoffs in size-specific growth and mortality rates between the aquatic and terrestrial stages. A limitation of these models is that they do not incorporate evolutionary phenomena that are associated with metapopulation structure. In this work I address components of the evolution of complex life cycles (CLCs) that are tied to the metapopulation dynamics of amphibians that use seasonal wetlands that vary in hydroperiod. In particular, I describe how selection for the minimum length of the larval period affects metapopulation viability and the selection/migration equilibrium. Selection to increase the minimum length of the larval period functionally reduces the number of viable breeding sites on the landscape, increases the average distance between neighboring sites, and increases the risk of metapopulation extinction. Within a metapopulation, asymmetric gene flow between populations that are adapted to different hydroperiods tends to swamp local selection for long larval periods at sites with long hydroperiods. The evolutionary stability of CLCs of many species with metapopulation structure may reflect the fact that extremely small metamorphs cannot survive on land, while lineages with long larval periods incur a high risk of metapopulation extinction. I encourage theorists to more carefully consider how life history traits and metapopulation viability are related for these and other taxa.     

集合种群理论在生态恢复中的应用

环境问题的改善是生态与环境学家所面临的挑战之一 ,其核心是生态系统的稳定性和平衡性遭到极大的破坏 ,最明显的表现是生境破碎和栖息地丧失。本文探讨了集合种群理论的形成与成因 ,概述了该理论发展的最新成果及应用前景。在集合种群理论应用于生态恢复实践的论述中 ,阐述了一些原则性问题 ,包括集合种群平衡观、最小可存活集合种群、最适斑块密度以及高质量生境斑块等 ,以求在人们设计物种保护和恢复对策时 ,有一定的指导价值。     

Dynamics of range margins for metapopulations under climate change

We link spatially explicit climate change predictions to a dynamic metapopulation model. Predictions of species'' responses to climate change, incorporating metapopulation dynamics and elements of dispersal, allow us to explore the range margin dynamics for two lagomorphs of conservation concern. Although the lagomorphs have very different distribution patterns, shifts at the edge of the range were more pronounced than shifts in the overall metapopulation. For Romerolagus diazi (volcano rabbit), the lower elevation range limit shifted upslope by approximately 700 m. This reduced the area occupied by the metapopulation, as the mountain peak currently lacks suitable vegetation. For Lepus timidus (European mountain hare), we modelled the British metapopulation. Increasing the dispersive estimate caused the metapopulation to shift faster on the northern range margin (leading edge). By contrast, it caused the metapopulation to respond to climate change slower, rather than faster, on the southern range margin (trailing edge). The differential responses of the leading and trailing range margins and the relative sensitivity of range limits to climate change compared with that of the metapopulation centroid have important implications for where conservation monitoring should be targeted. Our study demonstrates the importance and possibility of moving from simple bioclimatic envelope models to second-generation models that incorporate both dynamic climate change and metapopulation dynamics.     

Test of mathematical assumptions behind the 'incidence function' estimation process of metapopulations' dynamic parameters.

I question Hanski's [I. Hanski, A practical model of metapopulation dynamics, J. Animal Ecol. 63 (1994) 151] assumption that incidence functions are relevant approximations of the equilibrium dynamics of stochastic metapopulation models to estimate models' parameters based on snapshot data. Based on ten different metapopulation models, this assumption is found to be at least partly unjustified when referring to the asymptotic behaviour of the models. This leads me to recommend the use of explicit extinction-colonisation transition probabilities and process data (rather than snapshot data) in the estimation process of metapopulation models.