Pines and paddocks: socioecology and population genetics of marsupials in fragmented systems

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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 …

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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  • 1. The Environment Institute Where ideas grow Dr Melanie Lancaster Pines and paddocks: Socioecology and population genetics of marsupials in fragmented systems
  • 2. Pines and paddocks: Socio-ecology and population genetics of marsupials in fragmented south-eastern Australia Melanie Lancaster Earth and Environmental Sciences The University of Adelaide Steven J.B. Cooper, Susan Carthew, Andrea C. Taylor
  • 3. Molecular Ecology INDIVIDUAL POPULATION SPECIES 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.
  • 4. 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?
  • 5. PhD research – species identification Genetic screening of individuals => 70 identification to a source species or hybrid class 60 50 % PUPS 40 30 20 10 0 1992 1994 1996 1998 2000 2002 YEAR Lancaster et al. (2006) Molecular Ecology
  • 6. PhD research – mating systems Genetic analysis of paternity => identify fitness cost to hybridisation Lancaster et al. (2007) Molecular Ecology
  • 7. Molecular Ecology INDIVIDUAL POPULATION SPECIES 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.
  • 8. 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 ecology Multi-species approaches
  • 9. Fragmentation in Australia Source: http://adl.brs.gov.au/anrdl/metadata/overviews/alccdr9ab__004/alccdr9ab__00411a10b.pdf
  • 10. 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
  • 11. Study site The “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
  • 12. Mammal species Arboreal and terrestrial Sugar 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
  • 13. 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
  • 14. ARC Linkage Conservation genetics and socio-ecology of marsupials in fragmented populations of south-eastern South Australia: towards a regional biodiversity management plan A/Prof Sue Carthew, Dr Steve Cooper, Dr Andrea Taylor PARTNERS: To assess the impacts of forest fragmentation on population processes in key marsupial species
  • 15. Fragmentation case studies 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 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
  • 16. 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
  • 17. Study site 10 23 11 21 18 30 10 35 23 20 47 7 23 15 78 43 74
  • 18. 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
  • 19. 1. Genetic Diversity Have 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
  • 20. 2. Population structure Do 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
  • 21. 2. Population structure Do possums move through paddocks and roadside vegetation? 8 distinct genetic clusters identified Significant pop structure and isolation Limited evidence of gene flow/dispersal
  • 22. Pop Differentiation HH HS L P REN SG W WD HH HS 0.05 L 0.19 0.12 P 0.11 0.03 0.17 REN 0.10 0.03 0.13 0.00 SG 0.08 0.03 0.12 0.03 0.04 W 0.06 0.04 0.14 0.05 0.07 0.04 WD 0.09 0.02 0.13 0.02 0.02 0.03 0.05 BG G HC M PS RR SQ REN BG G 0.08 HC 0.08 0.07 Population pair-wise FST shows all M 0.06 0.04 0.08 pops except P and R as significantly PS 0.04 0.08 0.11 0.05 RR 0.08 0.11 0.09 0.08 0.09 different (most p < 0.0001) SQ 0.07 0.05 0.07 0.02 0.06 0.07 REN 0.03 0.04 0.06 0.03 0.04 0.05 0.03 Patches vs Continuous R1 R2 R3 No sig difference between R1 and R2 R1 0.12 <0.0001 (2.5 km) R2 0.007 <0.01 Sig. Differentiation of R3 from other R3 0.038 0.033 patches (3 km)
  • 23. 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
  • 24. PINE PADDOCKS P and SG not sig Males Males 0.600 0.300 0.400 0.200 0.100 0.200 Mean 0.000 r 0.000 U -0.100 -0.200 L -0.200 -0.400 BG G HC M PS RR SQ HH HS L P SG W WD Females Females 0.800 0.300 0.600 0.200 0.400 0.100 r 0.200 0.000 0.000 -0.100 -0.200 -0.200 HH HS L P SG W WD BG G HC Patch M PS RR SQ Patch Continuous Forest All others sig. higher relatedness than 0.300 0.200 expected by chance 0.100 Mean Both sexes show this trend r 0.000 U -0.100 L -0.200 R1 M R2 M R3 M R1 F R2 F R3 F cf continuous forest neither females or Patch males show this pattern
  • 25. Summary • 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
  • 26. Recommendations and What next? – 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
  • 27. Acknowledgements Field volunteers for valuable Australian Research Council Linkage assistance with possuming Grants Scheme, with partners: • Department for the Environment and Heritage Martin Pepper for providing • Forestry SA photographs • Hancock Victorian Plantations • Nature Foundation of South Kathy Saint for assistance Australia with microsatellite development • South Australian Museum
  • 28. The Environment Institute Where ideas grow Next Seminar: 27 November Professor Kym Anderson Regional implications of climate change for the Australian wine industry