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Redefining rainforest refugia

Understanding how rainforest communities are assembled, and why these assemblages change through time is an important ecological question.

In particular, we are interested in identifying which rainforest areas have persisted through time (i.e. which areas are long-term refugia). Identifying refugia and understanding the characteristics that make vegetation persist can help us understand which areas are more vulnerable, and identify priority areas for biodiversity conservation.

We use a range of approaches to identify long-term rainforest refugia. Overall numbers of species within a community, their relatedness, their functional and genetic diversities, are all useful indicators of long-term community stability. Greater diversity (phylogenetic, functional and genetic) accumulates in stable habitats (refugia) where species interact in conserved niches. While higher uniformity is more common in recolonised areas, where selection for specific attributes reflects high environmental disturbance.

Current research

We are currently using different interpretative methods for identifying rainforest refugia. We combine environmental models that compare the availability of habitat for a large number of rainforest species now and in the past (during the last glacial maximum). Then we measure genomic diversity across these same species to assess if the areas modeled as most environmentally stable also display maximum genetic diversity. We can also obtain an estimate of the time since the individuals of a species within a local community last shared a common ancestor.

Applying this across multiple species provide us with a temporal understanding of the assembly process of the current communities.

Some of our relevant publications:

  1. Rossetto M, McPherson H, Siow J, Kooyman R, van der Merwe M, Wilson PD (2015) Where did all the trees come from? A novel multidisciplinary approach reveals the impacts of biogeographic history and functional diversity on rain forest assembly. Journal of Biogeography 42: 2172-2186.
  2. Rossetto M, Yap JYS, Kooyman R, Laffan S (2015) From ratites to rats: the size of fleshy fruits shapes species distributions and continental rainforest assembly. Proceedings of the Royal Society B 282:20151998.
  3. Kooyman RM, Rossetto M, Sauquet H, Laffan SW (2013) Landscape Patterns in Rainforest Phylogenetic Signal: Isolated Islands of Refugia or Structured Continental Distributions? PLOS one 8(12): e80685.
  4. Mellick R, Lowe A, Allen C, Hill RS, Rossetto M (2012) Palaeodistribution modelling and genetic evidence highlight differential post-glacial range shifts of a rain forest conifer distributed across a broad latitudinal gradient. Journal of Biogeography 39: 2292-2302.
  5. Mellick, R, Rossetto M, Allen C, Wilson PD, Hill RS, Lowe A (2013) Intraspecific divergence associated with a biogeographic barrier and climatic models show future threats and long-term decline of a rainforest conifer. The Open Conservation Biology Journal 7: 1-10.
  6. Mellick R, Wilson PD, Rossetto M (2013) Post-glacial spatial dynamics in a rainforest biodiversity hot spot. Diversity 5: 124-138.
  7. Kooyman R, Rossetto M, Cornwell W, Westoby M (2011) Phylogenetic tests of community assembly across regional to continental scales in tropical and sub-tropical rainforests. Global Ecology and Biogeography 20(5): 707-716.