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

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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

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7478

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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

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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

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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

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L

-0.200

0.000

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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

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Professor Kym Anderson

Regional implications of climate change for the Australian wine industry