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Spatial Population Structure (spatial + population_structure)

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Life Sciences100%

Selected Abstracts

Spatial population structure of a specialist leaf-mining moth

JOURNAL OF ANIMAL ECOLOGY, Issue 4 2008
Sofia Gripenberg
Summary 1The spatial structure of natural populations may profoundly influence their dynamics. Depending on the frequency of movements among local populations and the consequent balance between local and regional population processes, earlier work has attempted to classify metapopulations into clear-cut categories, ranging from patchy populations to sets of remnant populations. In an alternative, dichotomous scheme, local populations have been classified as self-sustaining populations generating a surplus of individuals (sources) and those depending on immigration for persistence (sinks). 2In this paper, we describe the spatial population structure of the leaf-mining moth Tischeria ekebladella, a specialist herbivore of the pedunculate oak Quercus robur. We relate moth dispersal to the distribution of oaks on Wattkast, a small island (5 km2) off the south-western coast of Finland. 3We build a spatially realistic metapopulation model derived from assumptions concerning the behaviour of individual moths, and show that the model is able to explain part of the variation in observed patterns of occurrence and colonization. 4While the species was always present on large trees, a considerable proportion of the local populations associated with small oaks showed extinction,recolonization dynamics. The vast majority of moth individuals occur on large trees. 5According to model predictions, the dominance of local vs. regional processes in tree-specific moth dynamics varies drastically across the landscape. Most local populations may be defined broadly as ,sinks', as model simulations suggest that in the absence of immigration, only the largest oaks will sustain viable moth populations. Large trees in areas of high oak density will contribute most to the overall persistence of the metapopulation by acting as sources of moths colonizing other trees. 6No single ,metapopulation type' will suffice to describe the oak,moth system. Instead, our study supports the notion that real populations are often a mix of earlier identified categories. The level to which local populations may persist after landscape modification will vary across the landscape, and sweeping classifications of metapopulations into single categories will contribute little to understanding how individual local populations contribute to the overall persistence of the system. [source]

Spatial population structure in a patchily distributed beetle

MOLECULAR ECOLOGY, Issue 4 2001
Tomas Roslin
Abstract The dynamics and evolution of populations will critically depend on their spatial structure. Hence, a recent emphasis on one particular type of structure , the metapopulation concept of Levins , can only be justified by empirical assessment of spatial population structures in a wide range of organisms. This paper focuses on Aphodius fossor, a dung beetle specialized on cattle pastures. An agricultural database was used to locate nearly 50 000 local populations of A. fossor in Finland. Several independent methods were then used to quantify key processes in this vast population system. Allozyme markers and mitochondrial DNA (mtDNA) sequences were applied to examine genetic differentiation of local populations and to derive indirect estimates of gene flow. These estimates were compared to values expected on the basis of direct observations of dispersing individuals and assessments of local effective population size. Molecular markers revealed striking genetic homogeneity in A. fossor. Differentiation was only evident in mtDNA haplotype frequencies between the isolated Åland islands and the Finnish mainland. Thus, indirect estimates of gene flow agreed with direct observations that local effective population size in A. fossor is large (hundreds of individuals), and that in each generation, a substantial fraction (approximately one-fifth) of the individuals move between populations. Large local population size, extreme haplotype diversity and a high regional incidence of A. fossor all testify against recurrent population turnover. Taken together, these results provide strong evidence that the whole mainland population of A. fossor is better described as one large ,patchy population', with substantial movement between relatively persistent local populations, than as a classical metapopulation. [source]

Dispersal ability and host-plant characteristics influence spatial population structure of monophagous beetles

ECOLOGICAL ENTOMOLOGY, Issue 1 2005
Matthew J. St Pierre
Abstract., 1. Dispersal plays an integral role in determining spatial population structure and, consequently, the long-term survival of many species. Theoretical studies indicate that dispersal increases with population density and decreasing habitat stability. In the case of monophagous insect herbivores, the stability of host-plant populations may influence their spatial population structure. 2. The tallgrass prairie in Iowa, U.S.A. is highly fragmented and most prairie insects face a landscape with fewer habitat patches and smaller host-plant populations than 150 years ago, potentially making dispersal between patches difficult. Some herbivores, however, use native plant species with weedy characteristics that have increased in abundance because of disturbances. 3. Mark,recapture data and presence,absence surveys were used to examine dispersal and spatial population structure of two monophagous beetles with host plants that exhibit different population stability and have responded differently to fragmentation of tallgrass prairie. 4. Chrysochus auratus Fabricius exhibits a patchy population structure and has relatively large dispersal distances and frequencies. Its host plant is variable locally in time and space, but is more abundant than 150 years ago. The other species, Anomoea laticlavia Forster, exhibits a metapopulation or non-equilibrium population structure and has relatively small dispersal distances and frequencies. Its host-plant populations are stable in time and space. 5. The results indicate that dispersal ability of monophagous beetles reflects the life-history dynamics of their host plants, but the spatial population structure exhibited today is strongly influenced by how the host plants have responded to the fragmentation process over both time and space. [source]

Spatial population structure of a specialist leaf-mining moth

JOURNAL OF ANIMAL ECOLOGY, Issue 4 2008
Sofia Gripenberg
Summary 1The spatial structure of natural populations may profoundly influence their dynamics. Depending on the frequency of movements among local populations and the consequent balance between local and regional population processes, earlier work has attempted to classify metapopulations into clear-cut categories, ranging from patchy populations to sets of remnant populations. In an alternative, dichotomous scheme, local populations have been classified as self-sustaining populations generating a surplus of individuals (sources) and those depending on immigration for persistence (sinks). 2In this paper, we describe the spatial population structure of the leaf-mining moth Tischeria ekebladella, a specialist herbivore of the pedunculate oak Quercus robur. We relate moth dispersal to the distribution of oaks on Wattkast, a small island (5 km2) off the south-western coast of Finland. 3We build a spatially realistic metapopulation model derived from assumptions concerning the behaviour of individual moths, and show that the model is able to explain part of the variation in observed patterns of occurrence and colonization. 4While the species was always present on large trees, a considerable proportion of the local populations associated with small oaks showed extinction,recolonization dynamics. The vast majority of moth individuals occur on large trees. 5According to model predictions, the dominance of local vs. regional processes in tree-specific moth dynamics varies drastically across the landscape. Most local populations may be defined broadly as ,sinks', as model simulations suggest that in the absence of immigration, only the largest oaks will sustain viable moth populations. Large trees in areas of high oak density will contribute most to the overall persistence of the metapopulation by acting as sources of moths colonizing other trees. 6No single ,metapopulation type' will suffice to describe the oak,moth system. Instead, our study supports the notion that real populations are often a mix of earlier identified categories. The level to which local populations may persist after landscape modification will vary across the landscape, and sweeping classifications of metapopulations into single categories will contribute little to understanding how individual local populations contribute to the overall persistence of the system. [source]

Population genetics of the black ant Formica lemani (Hymenoptera: Formicidae)

BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2009
PERTTU SEPPÄ
Colony kin structure and spatial population structure were studied in multiple populations of the ant Formica lemani, using allozymes and DNA microsatellites. Average genetic relatedness between nestmate workers varied little between populations (r = 0.51,0.76), indicating that the average colony kin structure was relatively simple. Worker genotypes could not be explained with a single breeding pair in all nests, however, and the distribution of relatedness estimates across nests was bimodal, suggesting that single- and multi-queen colonies co-occur. We studied spatial population structure in a successional boreal forest system, which is a mixture of different aged habitats. Newly clear-cut open habitat patches are quickly colonized by F. lemani, where it is able to persist for a limited number of generations. Newly-founded populations showed signs of a founder effect and spatial substructuring, whereas older populations were more homogenous. This suggests that new populations are founded by a limited number of colonizers arriving from more than one source. Genetic differentiation among local populations was minor, indicating strong migration between them. There were, however, indications of both isolation by distance and populations becoming more isolated as habitat patches grew older. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 97, 247,258. [source]

Spatial population structure in a patchily distributed beetle

MOLECULAR ECOLOGY, Issue 4 2001
Tomas Roslin
Abstract The dynamics and evolution of populations will critically depend on their spatial structure. Hence, a recent emphasis on one particular type of structure , the metapopulation concept of Levins , can only be justified by empirical assessment of spatial population structures in a wide range of organisms. This paper focuses on Aphodius fossor, a dung beetle specialized on cattle pastures. An agricultural database was used to locate nearly 50 000 local populations of A. fossor in Finland. Several independent methods were then used to quantify key processes in this vast population system. Allozyme markers and mitochondrial DNA (mtDNA) sequences were applied to examine genetic differentiation of local populations and to derive indirect estimates of gene flow. These estimates were compared to values expected on the basis of direct observations of dispersing individuals and assessments of local effective population size. Molecular markers revealed striking genetic homogeneity in A. fossor. Differentiation was only evident in mtDNA haplotype frequencies between the isolated Åland islands and the Finnish mainland. Thus, indirect estimates of gene flow agreed with direct observations that local effective population size in A. fossor is large (hundreds of individuals), and that in each generation, a substantial fraction (approximately one-fifth) of the individuals move between populations. Large local population size, extreme haplotype diversity and a high regional incidence of A. fossor all testify against recurrent population turnover. Taken together, these results provide strong evidence that the whole mainland population of A. fossor is better described as one large ,patchy population', with substantial movement between relatively persistent local populations, than as a classical metapopulation. [source]