Stéphanie Chauvet & Barbara Giles Umeå University and Groningen University
THE NATURAL CONTEXT
Natural landscape is a complex mosaic of habitats, due to: ÀBiological diversity and complexity ÀHabitat fragmentation by human activity
THE NATURAL CONTEXT
Natural landscape is a complex mosaic of habitats, due to: ÀBiological diversity and complexity ÀHabitat fragmentation by human activity Specific habitat and resource requirements: ÀSuitable and unsuitable habitats ÀFragmented distribution
THE NATURAL CONTEXT
Natural landscape is a complex mosaic of habitats, due to: ÀBiological diversity and complexity ÀHabitat fragmentation by human activity Specific habitat and resource requirements: ÀSuitable and unsuitable habitats ÀFragmented distribution ⇒ Population dynamics described by metapopulation models
METAPOPULATION DYNAMICS 2 determinant parameters: ÀExtinction rate - stochastic events - demographic parameters - successional stages ÀColonization rate (or dispersal rate) - dispersal ability - distance between populations - features of the landscape
DISPERSAL RATES
DISPERSAL RATES
DISPERSAL RATES
DISPERSAL RATES
Lower dispersal rate ⇒
Higher genetic differentiation
DISPERSAL RATES
Lower dispersal rate ⇒ Long distance seed dispersal ⇒
Higher genetic differentiation Colonization of isolated habitats
HYPOTHESIS TESTING
Genetic differentiation at local scale À distance isolation À effect of ”strict” isolation (by water) À effect of patch characteristics
HYPOTHESIS TESTING
Genetic differentiation at local scale À distance isolation À effect of ”strict” isolation (by water) À effect of patch characteristics Colonisation process of isolated habitat (islands) À genetic diversity on islands À number of founding events À origin of founders
STUDY SPECIES Mycelis muralis, Asteraceae: - ”dandelion” like, with a basal rosette of leaves - flowering stem with many capitula
STUDY SPECIES Mycelis muralis, Asteraceae: - ”dandelion” like, with a basal rosette of leaves - flowering stem with many capitula - five seeds per capitula
STUDY SPECIES Mycelis muralis, Asteraceae: - ”dandelion” like, with a basal rosette of leaves - flowering stem with many capitula - five seeds per capitula
Seed morphology: - wind dispersed
< 1 cm
STUDY AREA
Gävle region
coastal area island and mainland sites
LEAF COLLECTION (1)
21 sites: À 7 islands (
)
separated by insuitable areas
Gävle
À 11
mainlands ( )
separated by potential habitats
5 km
À 3 more mainlands (further north)
LEAF COLLECTION (2)
À samples size / site 30 < N < 300
Gävle
5 km
LEAF COLLECTION (2)
À samples size / site 30 < N < 300 À hierarchical sampling > site Gävle
>> patches >>> sub-patches
5 km
LEAF COLLECTION (2)
À samples size / site 30 < N < 300 À hierarchical sampling > site Gävle
>> patches >>> sub-patches À geographic location all sub-patches 5 km
LEAF COLLECTION (2)
À samples size / site 30 < N < 300 À hierarchical sampling > site Gävle
>> patches >>> sub-patches À geographic location all sub-patches 5 km
À habitat
descriptors
OPEN AND EXPOSED HABITAT
Island
Mainland
IN MIXED FOREST
Island
Mainland
IN CONIFEROUS FORESTS
Island
Mainland
IN BUSHES
Island
ALONG ROADS
Mainland
GENETIC ANALYSIS
Sample size: 20 individuals / 3 large islands 10 individuals / other populations (except 5 pop.) ⇒ N = 215
GENETIC ANALYSIS
Sample size: 20 individuals / 3 large islands 10 individuals / other populations (except 5 pop.) ⇒ N = 215
BUT: because of missing data ⇒ N = 147
GENETIC ANALYSIS
Sample size: 20 individuals / 3 large islands 10 individuals / other populations (except 5 pop.) ⇒ N = 215
BUT: because of missing data ⇒ N = 147 Preliminary results: - small sample sizes (allelic richness function of sample size) - missing resolution within site
GENETIC ANALYSIS
Sample size: 20 individuals / 3 large islands 10 individuals / other populations (except 5 pop.) ⇒ N = 215
BUT: because of missing data ⇒ N = 147 Preliminary results: - small sample sizes (allelic richness function of sample size) - missing resolution within site ⇒
Interpretation may change with increased samples
HYPOTHESIS TESTING
Genetic differentiation at local scale À distance isolation À effect of ”strict” isolation (by water) À effect of patch characteristics Colonisation process of isolated habitat (islands) À genetic diversity on islands À number of founding events À origin of founders
GENETIC ANALYSIS
Conducted for 11 microsatellites loci: Loc 4 → 4 alleles
⇒ Founder effects are affecting all the populations...
INSULARITY EFFECT Expected effect 1: Lower genetic diversity on islands
Expected effect 2: Fewer rare alleles on islands
INSULARITY EFFECT Expected effect 1: Lower genetic diversity on islands ⇒ No (Mann-Whitney U-test non significant) Expected effect 2: Fewer rare alleles on islands
INSULARITY EFFECT Expected effect 1: Lower genetic diversity on islands ⇒ No (Mann-Whitney U-test non significant) Expected effect 2: Fewer rare alleles on islands N. of alleles
N. of alleles
16
16
Billan
12 8 4
Eggegrund
12 8 4 0
0
0.95
0.85
0.75
0.65
0.55
0.45
0.35
0.25
0.15
0.05
0.95
0.85
0.75
0.65
0.55
0.45
0.35
0.25
0.15
0.05
Vastänan
N. of alleles
N. of alleles
16 9 6 3 0
Lövgrund
12 8 4 0
0.95
0.85
Allele frequency
0.75
0.65
0.55
0.45
0.35
0.25
0.15
0.05
0.95
0.85
0.75
0.65
0.55
0.45
0.35
0.25
0.15
0.05
Allele frequency
INSULARITY EFFECT Expected effect 1: Lower genetic diversity on islands ⇒ No (Mann-Whitney U-test non significant) ⇒ No
Expected effect 2: Fewer rare alleles on islands N. of alleles
N. of alleles
16
16
Billan
12 8 4
Eggegrund
12 8 4 0
0
0.95
0.85
0.75
0.65
0.55
0.45
0.35
0.25
0.15
0.05
0.95
0.85
0.75
0.65
0.55
0.45
0.35
0.25
0.15
0.05
Vastänan
N. of alleles
N. of alleles
16 9 6 3 0
Lövgrund
12 8 4 0
0.95
0.85
Allele frequency
0.75
0.65
0.55
0.45
0.35
0.25
0.15
0.05
0.95
0.85
0.75
0.65
0.55
0.45
0.35
0.25
0.15
0.05
Allele frequency
AND SO...
À What affects gene exchange between populations ??? isolation, population size, habitat characteristics...
AND SO...
À What affects gene exchange between populations ??? isolation, population size, habitat characteristics...
À How are the genotypes distributed over populations ???
