Where in the landscape are the refugia?

Can you spot the refugia? Neither could we by looking, but genetic data suggests protected side-slopes
Can you spot the refugia? Neither could we by looking, but genetic data suggests protected side-slopes

Locating areas where species will likely persist in future climate changes has recently become a conservation priority. How do we find these areas? A good first step is to look for places that species persisted through past climate changes (often termed ‘refugia’). We think we may have identified mini or micro-refugia for trees on deep, protected soils in the Grampians ranges, Victoria.

Clearly, the assumption that past refugia predict where future refugia will be depends on the nature of climate change. It is more likely if future climate change mimics past climate change, but may also be the case if past and future climates are different. Why? One reason is that local climates in refugia tend to be unique to their surroundings–buffering climate extremes for example. Or maybe they are mesic habitats in an arid landscape.

Populations of E. baxteri and closely related species on rocky, western slopes (‘West’ and ‘Endemics’) less diverse than eastern populations

In either case, we can better judge whether a past refugia will be a future one if we understand how local climates and landscape features are related to species persistence. We have a new paper out in the Journal of Biogeography that is an attempt at doing this. We looked within a regional refugium to find local conditions that match patterns of genetic diversity across the landscape.

We found populations of eucalypts on side slopes and valleys with deep, moist soils and protection from strong westerly winds were more genetically diverse than populations on exposed rocky slopes.

The Serra Range in the Grampians National Park in Victoria, Australia. The Grampians ranges are a cuesta formation with western dip slopes (left side of photo) and steep eastern slopes. Species may have persisted in the mesic east-facing slopes and disappeared from rocky west-facing slopes when climates were colder and drier

It seems fairly obvious that species would persist in nicer habitats, but this story was only revealed with genetics (not obvious from morphology or species composition). These findings help strengthen the case that mesic local climates in semi-arid Australia may serve as refugia.

The second part of this paper is about gene flow between species.. A complicated story for another day..

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