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The eleventh installment of the 2009 Science Seminar Series presented by Doctor Melanie Lancaster. The presentation is entitled "Pines and paddocks: socioecology and population genetics of marsupials in fragmented systems?"
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The Environment InstituteWhere ideas grow
Dr Melanie Lancaster
Pines and paddocks: Socioecology and population genetics of marsupials in fragmented systems
Pines and paddocks: Socio-ecology and population genetics of marsupials
in fragmented south-eastern Australia
Melanie LancasterEarth and Environmental Sciences
The University of Adelaide
Steven J.B. Cooper, Susan Carthew, Andrea C. Taylor
Molecular Ecology
Use of genetic tools to answer ecologically important questions
Identification of individuals to a source population
Population processes: migration, dispersal (ie. juvenile, sex-biased), GENE FLOW
Social structure: Mating systems, site fidelity, mate fidelity
Predict species responses to environmental changes, human impacts, etc.
INDIVIDUAL POPULATION SPECIES
Background (mine)PhD research
• Small population of fur seals on Macquarie Island
• Suspected interbreeding among three species– Different recolonisation histories
• Tissue samples collected from entire pup cohorts between 1992 and 2003
• Extensive observational data – territory locations,
pupping sites
• Species composition of the population
• Hybrids?
• Costs of hybridisation?
PhD research – species identification
0
10
20
30
40
50
60
70
1992 1994 1996 1998 2000 2002
% P
UPS
Lancaster et al. (2006) Molecular Ecology
Genetic screening of individuals => identification to a source species or
hybrid class
YEAR
PhD research – mating systems
Lancaster et al. (2007) Molecular Ecology
Genetic analysis of paternity => identify fitness cost to
hybridisation
Molecular Ecology
Use of genetic tools to answer ecologically important questions
Identification of individuals to a source population
Population processes: migration, dispersal (ie. juvenile, sex-biased), GENE FLOW
Social structure: Mating systems, site fidelity, mate fidelity
Predict species responses to environmental changes, human impacts, etc.
INDIVIDUAL POPULATION SPECIES
Forest Fragmentation
• Deforestation as old as the human occupation of the earth (Williams 2003)
• Process has affected more of the earth’s surface
Laurance and Beirregaard 1997:
• Preserve what we have• Plan the future landscape• Manage what is left
Species ecologyMulti-species approaches
Fragmentation in Australia
Source: http://adl.brs.gov.au/anrdl/metadata/overviews/alccdr9ab__004/alccdr9ab__00411a10b.pdf
SA - the Lower South-East
Pre-European Settlement• Flora diverse• E. baxteri and E. viminalis forests and woodlands dominated
Post-Settlement• Large areas cleared after WWII for softwood and agricultural land• 13 % native vegetation remains• Vegetation community composition changed• Remaining veg adapted to poor soils and poor drainage, incomplete representation• Remnants surrounded by cropland, pastures, pines
• Habitats that once supported native fauna may no longer be present
Study siteThe “Greater Green Triangle” region…when green is bad
• Largest wood fibre producing region in Australia• Dry, sclerophyll forests isolated by pine stands of various ages
Mammal species
Arboreal and terrestrialSugar gliders, yellow-bellied gliders, Common brushtail and
ringtail possums, microbats
Native rats, mice, southern brown bandicoot, yellow-footed Antechinus, wallabies (swamp, red-necked), kangaroos, wombats, echidnas
Consequences of fragmentation
Populations may become isolated if:• Distances between fragments too great to traverse
• Surrounding habitat too difficult to move through, acts as a barrier to dispersal
Individuals within populations do not move out of patch
• Populations become isolated over time and genetically differentiated from each other
• Within patches, results in increased relatedness, inbreeding, loss of genetic diversity Dispersal = ?gene flow
No dispersal = NO gene flow
To assess the impacts of forest fragmentation on population processes in key marsupial species
ARC LinkageConservation genetics and socio-ecology of marsupials
in fragmented populations of south-eastern South Australia: towards a regional biodiversity
management planA/Prof Sue Carthew, Dr Steve Cooper, Dr Andrea Taylor
PARTNERS:
To assess the impacts of forest fragmentation on population processes in key marsupial species
Fragmentation case studies
Sugar gliders (Mansoureh Malekien)• Restricted gene flow among some patches
• Effects greater in small patches isolated by pine
• Evidence for inbreeding in one patch from parentage analysis
Yellow-footed antechinus (Amanda McLean)• Some evidence of differentiation between populations
• Higher relatedness among females within patches than in continuous forest
Factors affecting population connectivity in fragmented landscapes:
• Age of regrowth forest
• Surrounding matrix
• Habitat shape, edge effects
• Lemurs, bird spp., gorillas, pademelons, bats, reptiles, frogs
Common ringtail possum
• Nocturnal arboreal marsupial• Broad distribution, abundant in a variety of forest habitats• Generalist herbivore – leaves, flowers, seeds of eucalypt spp., acacia spp.• Can build dreys• Survives in degraded habitats, found in fragmented landscapes
Study site
7
43
2315
7478
11
23
35
21
47
1030
23
18
20
10
Data collection
Site selection based on:
• patch size• distance to neighbouring patch (0.5->10 km)• 3 sites within continuous forest (distances between sites comparable)
• 251 possums patches within pine• 189 possums patches within agriculture• 48 from 3 continuous forest sites• Genotyped at 15 microsatellites• Analysed for genetic diversity and genetic differentiation
1. Genetic DiversityHave possums in patches retained
genetic diversity?
• HH and L sig. Lower allelic richness and heterozygosity
• Larger patches levels comparable to continuous forest
• Trend towards lower H and AR in ag patches
YES for some, NO for others, not related to patch size alone
2. Population structureDo possums move through the pine?
• Five distinct clusters identified from 8 populations
sampled
• No sub-structure within continuous forest
• HH and L genetically isolated
• P a subset of continuous forest
• SG, W and HS virtually same cluster membership
Yes, but pine hinders dispersal and gene flow
Less dispersal into small, isolated patches
Do possums move through paddocks and roadside vegetation?
2. Population structure
8 distinct genetic clusters identified
Significant pop structure and isolation
Limited evidence of gene flow/dispersal
Pop Differentiation
BG G HC M PS RR SQ RENBGG 0.08HC 0.08 0.07M 0.06 0.04 0.08PS 0.04 0.08 0.11 0.05RR 0.08 0.11 0.09 0.08 0.09SQ 0.07 0.05 0.07 0.02 0.06 0.07REN 0.03 0.04 0.06 0.03 0.04 0.05 0.03
HH HS L P REN SG W WDHHHS 0.05L 0.19 0.12P 0.11 0.03 0.17REN 0.10 0.03 0.13 0.00SG 0.08 0.03 0.12 0.03 0.04W 0.06 0.04 0.14 0.05 0.07 0.04WD 0.09 0.02 0.13 0.02 0.02 0.03 0.05
Population pair-wise FST shows all pops except P and R as significantly
different (most p < 0.0001)
Patches vs ContinuousR1 R2 R3
R1 0.12 <0.0001R2 0.007 <0.01R3 0.038 0.033
No sig difference between R1 and R2 (2.5 km)
Sig. Differentiation of R3 from other patches (3 km)
Dispersal patterns
• Mammalian patterns of dispersal– Sex-biased
– Males disperse as juveniles or young adults
– Females philopatric
• In fragmented landscapes these patterns may be disrupted if movement is inhibited
• Use genetic relatedness to look at patterns
-0.200
-0.100
0.000
0.100
0.200
0.300
BG G HC M PS RR SQ
Males
-0.200-0.1000.0000.1000.2000.300
BG G HC M PS RR SQPatch
Females
-0.200
-0.100
0.000
0.100
0.200
0.300
R1 M R2 M R3 M R1 F R2 F R3 F
r
Patch
Continuous Forest
Mean
U
L
-0.400
-0.200
0.000
0.200
0.400
0.600
HH HS L P SG W WD
r
Males
Mean
U
L
-0.200
0.000
0.200
0.400
0.600
0.800
HH HS L P SG W WD
r
Patch
Females
PINE PADDOCKS
All others sig. higher relatedness than expected by chance
Both sexes show this trend
cf continuous forest neither females or males show this pattern
P and SG not sig
• Intervening matrices appear to hinder dispersal and gene flow of possums– Less problematic in larger patches than smaller ones
– Larger patches have comparable genetic diversity to continuous forest
– Smaller patches HH and L show signatures of genetic isolation through low heterozygosity and lower allelic diversity.
• Findings of lower dispersal in both sexes in fragments important implications for social structure and mating system
• Pastoral land has greater impact on ringtail possums– Depend on several factors
• Patch size
• Age of pine
• Distance to neighbouring patch
• Time since isolation
Summary
– Modelling – which factors affect connectivity – position/distance/ size of patch but need to quantify
– Incorporate landscape features – roadside vegetation, plantations, grazed remnant vegetation. Circuitscape (uses algorithms from electronic circuit theory to predict patterns of dispersal)
– Incorporate more species
• Corridors to join patches on the periphery of landscapes
• Multiple potential sources of immigration important for genetic diversity
• Continued conservation of large patches that can
support viable populations to maintain remaining communities
Recommendations and What next?
Acknowledgements
Field volunteers for valuable
assistance with possuming
Martin Pepper for providing
photographs
Kathy Saint for assistance
with microsatellite development
Australian Research Council LinkageGrants Scheme, with partners:• Department for the Environment
and Heritage• Forestry SA• Hancock Victorian Plantations• Nature Foundation of South
Australia• South Australian Museum
The Environment InstituteWhere ideas grow
Next Seminar: 27 November
Professor Kym Anderson
Regional implications of climate change for the Australian wine industry