Individual genetic diversity correlates with the size and spatial isolation of natal colonies in a bird metapopulation

Abstract

The genetic consequences of small population size and isolation are of central concern in both population and conservation biology. Organisms with a metapopulation structure generally show effective population sizes that are much smaller than the number of mature individuals and this can reduce genetic diversity especially in small sized and isolated subpopulations. Here, we examine the association between heterozygosity and the size and spatial isolation of natal colonies in a metapopulation of lesser kestrels (Falco naumanni ). For this purpose, we used capture-mark-recapture data to determine the patterns of immigration into the studied colonies, and 11 highly polymorphic microsatellite markers that allowed us to estimate genetic diversity of locally born individuals. We found that individuals born in smaller and more isolated colonies were genetically less diverse. These colonies received a lower number of immigrants, supporting the idea that both reduced gene flow and small population size are responsible for the genetic pattern observed. Our results are particularly intriguing because the lesser kestrel is a vagile and migratory species with great movement capacity and dispersal potential. Overall, this study provides evidence of the association between individual heterozygosity and the size and spatial isolation of natal colonies in a highly mobile vertebrate showing relatively frequent dispersal and low genetic differentiation among local subpopulations.

Parental genetic characteristics and hatching success in a recovering population of Lesser Kestrels

“…Higher colony size could increase behavioral interference due to social interactions and this may result in reduced hatching rate due to extended periods of parental absence during incubation (Koenig 1982). On the other hand, higher colony sizes may increase the chance of finding a genetically complementary mate at specific coding loci not analyzed here, which may reduce the negative effects of genetic incompatibility on embryo development (Ortego et al 2008). Apart from colony size, male age also influenced hatching success, suggesting that male experience could be critical during incubation (Hamer and Furness 1991).…”

Metapopulation models for seasonally migratory animals

“…The spatially realistic migratory metapopulation model assumes that extinction rates will be negatively related to patch size, and some colonially breeding, migratory birds have been shown to meet this assumption [9,18]. However, unlike non-migratory metapopulations, the migratory model assumes that colonization occurs when individuals return from the opposite season and therefore predicts that colonization rates should be related to isolation from patches in the opposite season rather than in same season.…”

“…This appears never to have been tested for any migratory animals. Colonization rates of breeding patches are sometimes related to isolation from other breeding patches [9,18] and this is used as evidence that colonists are colonizing from other breeding patches. However, this finding could also be explained by noticing that breeding patches isolated from other breeding patches may also be more isolated from non-breeding patches.…”

“…The main obstacle is the difficulty of identifying demographically independent subpopulations in migratory species [7]; individuals occurring in separate subpopulations in the breeding season may be not separated in the non-breeding season, and vice versa. In the few cases in which metapopulation models have been applied to migratory animals, the assumption of a spatially homogeneous nonbreeding habitat is implicit [8,9]. When habitat in both seasons is spatially discrete, it becomes difficult to separate a population into demographically independent units, leaving uncertainty as to how, or whether, migratory species fit into the metapopulation concept [10].…”

Genetic structure confirms female-biased natal dispersal in the White-tailed Eagle population of the Carpathian Basin

“…By contrast, populations of a strictly philopatric species exhibit strong population genetic structure and show heterozygote deficiency on a metapopulation level (e.g. see Ortego et al (2008) for genetic structure of Lesser Kestrels Falco naumanni (Fleischer, 1818), and Monti et al (2018) for that of Osprey Pandion haliaeetus (Linnaeus, 1758)). …”