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Caught in the extinction vortex? Population dynamics and genetics in a metapopulation of dunlins Donald Blomqvist Dept. Zoology, Univ. Gothenburg, Sweden Small and isolated populations risk extinction for several reasons • Changes in demography and environment • Genetic threats - Inbreeding - Genetic drift - Mutation accumulation • Together form an ”extinction vortex” Inbreeding • More immediate threat than other genetic factors • Related parents produce more homozygous offspring: expression of recessive, detrimental alleles • Reduction in individual fitness: inbreeding depression • Well documented in plants and animals Influence of inbreeding and loss of genetic diversity on extinction risk • Theoretically expected • Supported by computer simulations, lab experiments, and studies of plants and butterflies in the wild • Still few studies of natural populations The aim of our study Southern Dunlin Calidris alpina schinzii The Dunlin Circumpolar breeding distribution Winters in temperate or tropical areas Mean lifespan 5-7 years, max ~ 20 years Socially monogamous Several subspecies The Southern Dunlin Breeds in SE Greenland and NW Europe In the Baltic Sea region, confined to wet pastures and meadows Habitat loss - large population decline Endangered Study population Several interconnected, local populations form a metapopulation 150 12 120 Area (ha) Number of immigrants 16 8 4 90 60 30 0 0 50 100 150 0 200 16 12 8 4 0 0 10 20 30 40 50 60 Distance nearest site (km) Distance nearest site (km) Number of immigrants Area (ha) 30 25 20 15 10 5 0 Extinct Not extinct More extinctions than re-colonizations of local populations The entire metapopulation is threatened by extinction Questions 1. Population decline associated with more matings between related individuals? 2. Fitness consequences? 3. Is habitat management sufficient for preserving the Southern Dunlin? Data Long-term study: Population, pedigree and individual fitness data Two types of molecular markers: • DNA fingerprinting: Genetic similarity of mates • Microsatellite genotyping (7 loci): Individual genetic diversity Questions 1. Population decline associated with more matings between related individuals? 2. Fitness consequences? 3. Is habitat management sufficient for preserving the Southern Dunlin? Increased frequency of matings between related individuals Mean genetic similarity % Incestuous matings 15 12 9 6 3 0 '93 '95 '97 '99 '01 '03 0.24 0.20 0.16 0.12 0.08 '93 '95 '97 '99 '01 '03 Year Year Pedigrees (141 pairs) DNA fingerprinting p = 0.038, 40 pairs Questions 1. Population decline associated with more matings between related individuals? 2. Fitness consequences? 3. Is habitat management sufficient for preserving the Southern Dunlin? Related parents suffer increased hatching failure Hatching success 1.0 0.8 0.6 0.4 0.2 0.0 0.0 0.1 0.2 0.3 0.4 0.5 Genetic similarity p = 0.024 36 pairs Mean % heterozygous loci 80 57 p = 0.023 70 60 7 50 40 Hatched Not hatched More homozygous chicks die earlier Homozygous chicks are less likely to survive to breeding age % Individuals 100 Heterozygous Homozygous 23 80 18 60 11 40 20 3 p = 0.032 Returned Not returned Questions 1. Population decline associated with more matings between related individuals? 2. Fitness consequences? 3. Is habitat management sufficient for preserving the Southern Dunlin? Protective nest cages 2001-2004 ...yet the population continues to decline 40 1.0 Number of pairs Nest survival probability Cages improve nest survival... 0.8 0.6 0.4 35 30 25 20 15 0.2 No Yes Nest protection p = 0.048, 86 nests '93 '95 '97 '99 '01 '03 Year Conclusions The population decline of the Southern Dunlin has serious genetic consequences Habitat management seems insufficient for preserving the Southern Dunlin Ignoring genetics will underestimate extinction risks and may lead to inappropriate conservation measures Financial support Swedish Research Council (Formas) County Administration Board of Halland, Sweden Co-workers L.-Å. Flodin H. Hirsimäki O. C. Johansson M. Larsson A. Pauliny U. Unger J. Wallander