Patchy population structure in a short‐distance migrant: evidence from genetic and demographic data

Abstract

Species often occur in subdivided populations as a consequence of spatial heterogeneity of the habitat. To describe the spatial organization of ubpopulations, existing theory proposes three main population models: patchy population, metapopulation and isolated populations. These models differ in their predicted levels of connectivity among subpopulations, and in the risk that a subpopulation will go extinct. However, spatially discrete subpopulations are commonly considered to be organized as metapopulations, even though explicit tests of metapopulation assumptions are rare. Here, we test predictions of the three models on the basis of demographic and genetic data, a combined approach so far surprisingly little used in mobile organisms. From 2002 to 2005, we studied nine subpopulations of the wetland-restricted reed bunting (Emberiza schoeniclus) in the southeastern part of the Canton Zurich (Switzerland), from which local declines of this species have been reported. Here, wetlands are as small as 2.7 ha and separated through intensively used agricultural landscapes. Demographic data consisted of dispersal of colour-banded individuals among subpopulations, immigration rates and extinction-/recolonization dynamics. Genetic data were based on the distribution of genetic variability and gene flow among subpopulations derived from the analysis of nine microsatellite loci. Both demographic and genetic data revealed that the patchy population model best described the spatial organization of reed bunting subpopulations. High levels of dispersal among subpopulations, high immigration into the patchy population, and genetic admixture suggested little risk of extinction of both subpopulations and the entire patchy population. This study exemplifies the idea that spatially discrete subpopulations may be organized in ways other than a metapopulation, and hence has implications for the conservation of subpopulations and species. AbstractSpecies often occur in subdivided populations as a consequence of spatial heterogeneity of the habitat. To describe the spatial organization of subpopulations, existing theory proposes three main population models, which predict different levels of connectivity among and extinction risks of subpopulations: patchy population, metapopulation and isolated populations. However, spatially discrete subpopulations are commonly considered to be organized as metapopulations, although explicit tests of metapopulation assumptions are rare.Here, we test predictions of the three models on the basis of demographic and genetic data, a combined approach so far surprisingly little used in mobile organisms. This study exemplifies that spatially discrete subpopulations may be organized in ways other than a metapopulation, which has implications for the conservation of subpopulations and species.Patchy population structure in Reed buntings 3

Genetic diversity of tufted ducks (Aythya fuligula, Anatidae) in Eastern Europe

“…In many cases, the aim of conducting genetic analysis of migratory birds is to reconstruct their recent evolutionary history [51], search for the genetic evidence of past population expansions [52] and/or assess the degree of divergence in population genetic structure across a breeding range [53]. Genetic analysis is useful for inferring patterns of connectivity between breeding and overwintering sites as well as population mixing during the winter season [54].…”

“…The first groups of breeding tufted ducks were recorded in the early 20 th century at the western and eastern borders of Lithuania simultaneously, with further expansion of breeding birds into the central part of the country [64,65]. The quick expansion of a species range due to climate change or natural barriers often leads to a rise in genetic variability in recently established sub-populations [51,53]. The history of the establishment of the tufted duck as a breeding species in the eastern Baltic region is consistent with the results of the genetic analysis obtained in our study.…”

Source–sink status of small and large wetland fragments and growth rate of a population network

“…For further details on the study area, see Pasinelli and Schiegg ( 2006 ), Pasinelli et al . ( 2008 ), andMayer et al . ( 2009 ).…”

Genetic diversity and population structure of the range restricted rock firefinch Lagonosticta sanguinodorsalis

“…Species living in naturally fragmented habitats have however evolved as naturally fragmented populations, whereas other species have seen their distribution being fragmented due to recent anthropogenic impingements. The reed bunting (Emberiza schoeniclus; Mayer et al 2009) and the great reed warbler (Acrocephalus arundinaceus; Hansson et al 2000Hansson et al , 2002Hansson et al , 2008 for example, inhabit mosaics of wetlands, so it is likely that their population structure depended to a large extent on the size and connectivity of available wetlands prior to recent anthropogenic habitat alterations. In contrast, the red-cockaded woodpecker (Picoides borealis; Jackson 1978) and the chestnut-backed antbird (Myrmeciza exsul; Woltmann et al 2012) are two of many examples of species that probably inhabited large continuous habitats, but currently exist in small and isolated pockets within their today strongly human-influenced range.…”