Ilkka Hanski

Metapopulation biology : ecology, genetics, and evolution

Conceptual Foundation: Introduction. Empirical Evidence for Metapopulation Dynamics. Metapopulation Dynamics and Landscape Ecology. Theory of Metapopulation Dynamics. Metapopulation Dynamics: Form Concepts and Observations to Predictive Models. Structures Metapopulation Models. Two-Species Metapopulation Models. From Metapopulation Dynamics to Community Structure: Some Consequences of Spatial Heterogeneity. Genetic Effective Size of a Metapopulation. The Evolution of Metapopulations. Metapopulation Processes: Extinction Models for Local Populations. Studying Transfer Processes in Metapopulations: Immigration, Migration, And Colonization. Migration Within Metapopulations: The Impact Upon Local Population Dynamics. Evolution of Migration Rate and Other Traits: The Metapopulation Effect. Spatial Processes in Host-Parasite Genetics. Case Studies: Butterfly Metapopulations. Tritrophic Metapopulation Dynamics: A Case Study of Ragworth, The Cinnabar Moth, And the Parasitoid Cotesia Popularis. Spatially Correlated Dynamics in a Pika Metapopulation. A Case Study of Genetic Structure in a Plant Metapopulation. Subject Index.

Inbreeding and extinction in a butterfly metapopulation

It has been proposed that inbreeding contributes to the decline and eventual extinction of small and isolated populations,. There is ample evidence of fitness reduction due to inbreeding (inbreeding depression) in captivity and from a few experimental, and observational field studies,, but no field studies on natural populations have been conducted to test the proposed effect on extinction. It has been argued that in natural populations the impact of inbreeding depression on population survival will be insignificant in comparison to that of demographic and environmental stochasticity,. We have now studied the effect of inbreeding on local extinction in a large metapopulation of the Glanville fritillary butterfly (Melitaea cinxia). We found that extinction risk increased significantly with decreasing heterozygosity, an indication of inbreeding, even after accounting for the effects of the relevant ecological factors. Larval survival, adult longevity and egg-hatching rate were found to be adversely affected by inbreeding and appear to be the fitness components underlying the relationship between inbreeding and extinction. To our knowledge, this is the first demonstration of an effect of inbreeding on the extinction of natural populations. Our results are particularly relevant to the increasing number of species with small local populations due to habitat loss and fragmentation.

A practical model of metapopulation dynamics

This paper describes a novel approach to modelling of metapopulation dynamics. The model is constructed as a generalized incidence function, which describes how the fraction of occupied habitat patches depends on patch areas and isolations. The model may be fitted to presence/absence data from a metapopulation at a dynamic equilibrium between extinctions and colonizations. Using the estimated parameter values, transient dynamics and the equilibrium fraction of occupied patches in any system of habitat patches can be predicted. The significance of particular habitat patches for the long-term persistence of the metapopulation, for example, can also be evaluated

1 – The Metapopulation Approach, Its History, Conceptual Domain, and Application to Conservation

Publisher Summary This chapter reviews and analyzes the spread of the metapopulation concept to conservation biology and applications. The metapopulation concept has now been firmly established in population biology. Two key premises in this approach to population biology are that populations are spatially structured into assemblages of local breeding populations, and that migration among the local populations has some effect on local dynamics, including the possibility of population reestablishment following extinction. These premises contrast with those of standard models of demography, population growth, genetics, and community interaction that assume a panmictic population structure, with all individuals equally likely to interact with any others. The focus on metapopulations, combined with that on genetics, has led to the population and the species becoming the dominant levels of concern in conservation. It is striking that the recent explosion of interest in ecosystem management is quite antithetic to a primary interest in populations and to single species management. Ecosystem management and metapopulation models share a concern with landscapes and regions, rather than highly local settings, and one could imagine a landscape with a distribution of habitat patches that would maintain many metapopulations simultaneously.

Ecology, Genetics, and Evolution of Metapopulations

Table of contents Contributors Preface Introduction Chapter 1 Metapopulation biology: Past, present, and future Chapter 2 Metapopulation dynamics: Perspectives from landscape ecology Chapter 3 Continuous-space models for population dynamics Metapopulation ecology Chapter 4 Metapopulation dynamics in highly fragmented landscapes Chapter 5 Application of stochastic patch occupancy models to real metapopulations Chapter 6 From metapopulations to metacommunities Metapopulation genetics Chapter 7 Selection and drift in metapopulations Chapter 8 Metapopulations and coalescent theory Chapter 9 Metapopulation quantitative genetics: The quantitative genetics of population differentiation Evolutionary dynamics in metapopulations Chapter 10 Life history evolution in metapopulations Chapter 11 Selection in metapopulations: The co-evolution of phenotype and context Chapter 12 Speciation in metapopulations Integration and applications Chapter 13 Causes, mechanisms and consequences of dispersal Chapter 14 Mechanisms of population extinction Chapter 15 Multilocus genotype methods for the study of metapopulation processes Chapter 16 Ecological and evolutionary consequences of source-sink population dynamics Chapter 17 Metapopulation dynamics of infectious diseases Chapter 18 Towards a metapopulation concept for plants Chapter 19 Long-term study of a plant-pathogen metapopulation Chapter 20 Metapopulation dynamics in changing environments: Butterfly responses to habitat and climate change Chapter 21 Inferring pattern and process in small mammal metapopulations: Insights from ecological and genetic data Chapter 22 Metapopulation dynamics and reserve network design Chapter 23 Viability analysis for endangered metapopulations: A diffusion approximation approach Bibliography Index

Rapid transcriptome characterization for a nonmodel organism using 454 pyrosequencing

We present a de novo assembly of a eukaryote transcriptome using 454 pyrosequencing data. The Glanville fritillary butterfly (Melitaea cinxia; Lepidoptera: Nymphalidae) is a prominent species in population biology but had no previous genomic data. Sequencing runs using two normalized complementary DNA collections from a genetically diverse pool of larvae, pupae, and adults yielded 608 053 expressed sequence tags (mean length = 110 nucleotides), which assembled into 48 354 contigs (sets of overlapping DNA segments) and 59 943 singletons. blast comparisons confirmed the accuracy of the sequencing and assembly, and indicated the presence of c. 9000 unique genes, along with > 6000 additional microarray‐confirmed unannotated contigs. Average depth of coverage was 6.5‐fold for the longest 4800 contigs (348–2849 bp in length), sufficient for detecting large numbers of single nucleotide polymorphisms. Oligonucleotide microarray probes designed from the assembled sequences showed highly repeatable hybridization intensity and revealed biological differences among individuals. We conclude that 454 sequencing, when performed to provide sufficient coverage depth, allows de novo transcriptome assembly and a fast, cost‐effective, and reliable method for development of functional genomic tools for nonmodel species. This development narrows the gap between approaches based on model organisms with rich genetic resources vs. species that are most tractable for ecological and evolutionary studies.

Patch-occupancy dynamics in fragmented landscapes.

Recent work on the dynamics of species living In fragmented landscapes has produced much Information on patterns of habitat patch occupancy in a wide range of organisms. Building on an elementary Markov chain model of patch occupancy, a family of Incidence-function models can be constructed for particular kinds of metapopulations. These models can be parameterized with field data on patch occupancy, and the models can be used to make quantitative predictions about specific metapopulations. This approach provides a potentially powerful tool for the management of reserve networks and species living in fragmented landscapes.

METAPOPULATION DYNAMICS: EFFECTS OF HABITAT QUALITY AND LANDSCAPE STRUCTURE

Metapopulation dynamics have received much attention in conservation and population biology, but the standard approach has also been criticized for being too restrictive, as it is based on the effects of habitat patch area and isolation only. Here we demonstrate how the effects of habitat quality (extra environmental factors) and detailed landscape structure (described with GIS [Geographical Information System]) can be included in a spatially realistic metapopulation model, the incidence function model. Expanded models are tested with a large data set on the Glanville fritillary butterfly (Melitaea cinxia). The incidence function model supplemented with additional environmental factors revealed some new and confirmed some previously known interactions between M. cinxia and its environment. However, the ability of the additional environmental factors to explain the error in the fit of the basic model was generally low (≤15%). In the second variant of the basic model, landscape structure was used to modify effective patch isolations. This approach, though biologically appealing, failed to improve significantly the fit of the incidence function model. There are several possible reasons for this failure, including inaccurate satellite data, problems with habitat classification, and most importantly, generic problems in the modeling of migration. Our results demonstrate that additional complexity beyond the effects of habitat patch area and isolation does not necessarily improve the predictive power of a metapopulation model.

Environmental biodiversity, human microbiota, and allergy are interrelated

Rapidly declining biodiversity may be a contributing factor to another global megatrend—the rapidly increasing prevalence of allergies and other chronic inflammatory diseases among urban populations worldwide. According to the “biodiversity hypothesis,” reduced contact of people with natural environmental features and biodiversity may adversely affect the human commensal microbiota and its immunomodulatory capacity. Analyzing atopic sensitization (i.e., allergic disposition) in a random sample of adolescents living in a heterogeneous region of 100 × 150 km, we show that environmental biodiversity in the surroundings of the study subjects’ homes influenced the composition of the bacterial classes on their skin. Compared with healthy individuals, atopic individuals had lower environmental biodiversity in the surroundings of their homes and significantly lower generic diversity of gammaproteobacteria on their skin. The functional role of the Gram-negative gammaproteobacteria is supported by in vitro measurements of expression of IL-10, a key anti-inflammatory cytokine in immunologic tolerance, in peripheral blood mononuclear cells. In healthy, but not in atopic, individuals, IL-10 expression was positively correlated with the abundance of the gammaproteobacterial genus Acinetobacter on the skin. These results raise fundamental questions about the consequences of biodiversity loss for both allergic conditions and public health in general.

SMALL‐RODENT DYNAMICS AND PREDATION

The hypothesis that the regular multiannual population oscillations of boreal and arctic small rodents (voles and lemmings) are driven by predation is as old as the scientific study of rodent cycles itself. Subsequently, for several decades, the predation hypothesis fell into disrepute, possibly because the views about predation and rodent dy- namics were too simplistic. Here we review the work that has been done on the predation hypothesis primarily in Fennoscandia over the past decade. Models of predator-prey interaction have been constructed for the least weasel (Mustela nivalis) and the field vole (Microtus agrestis), which are considered to be the key specialist predator and the key prey species in the multispecies communities in the boreal forest region in Fennoscandia. The basic model has been parameterized with independent field data, and it predicts well the main features of the observed dynamics. An extension of the model also including generalist and nomadic avian predators predicts correctly the well- documented and striking geographic gradient in rodent oscillations in Fennoscandia, with the amplitude and cycle period decreasing from north to south. These geographic changes are attributed to the observed latitudinal change in the density of generalist and nomadic predators, which are expected to have a stabilizing effect on rodent dynamics. We review the other observational, modeling, and experimental results bearing on the predation hypothesis and conclude that it accounts well for the broad patterns in rodent oscillations in Fennoscandia. We discuss the application of the predation hypothesis to other regions in the northern hemisphere. The predation hypothesis does not make predictions about multiannual and latitudinal changes in body size, behavior, and demography of ro- dents, which may have some population-dynamic consequences. With the current evidence, however, we consider it unlikely that the phenotypic and genotypic composition of pop- ulations would be instrumental for generating the broad patterns in rodent oscillations.