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Mountain growth led to freshwater fish biodiversity in New Zealand - 15/12/2015

The growth of mountain ranges in the South Island has directly influenced the evolution of New Zealand freshwater fish species, according to new research from GNS Science and the Universities of Otago and Tasmania.

The findings are published online this week in Nature Geoscience. http://www.nature.com/ngeo/

Zoologists from the Universities of Otago and Tasmania reconstructing freshwater fish genetic relationships found increased biodiversity of freshwater fish across the South Island, but it wasn’t until they teamed up with geologists Professor Dave Craw (University of Otago) and Dr Phaedra Upton (GNS Science) that the reason behind the species distribution and diversity became clear.

What the authors realised was that distribution of fish species was correlated strongly with the principal tectonic and topographic zones of the South Island, which have distinct drainage catchments that separated fish populations.

The Hawkdun Ranges in Central Otago are an example of a tectonic barrier that has led to increased biodiversity of freshwater fish species in the South Island. Photo - Lloyd Homer, GNS Science

The Hawkdun Ranges in Central Otago are an example of a tectonic barrier that has led to increased biodiversity of freshwater fish species in the South Island. Photo - Lloyd Homer, GNS Science

Mountain ranges form at plate boundaries and the uplift of a new mountain range can separate biological populations, ultimately leading to the creation of a new species.

One of the authors of the paper, Dr Phaedra Upton of GNS Science used 3D numerical models to reconstruct how the mountains of the South Island rose over the past 25 million years, using a variety of geological and geophysical research from across the South Island.

The authors used the evolutionary tree of freshwater fish populations from South Island drainage catchments, based on over 1,000 specimens from more than 400 localities, to show that the fish DNA sequences diverge over time in tandem with the growth of the mountains.

Dr Upton says the relatively rapid rate of tectonic processes in the South Island over the past 25 million years is one reason we can observe how landscape evolution can shape biological diversity.

The uplift of the Southern Alps and the difference in tectonic development between the Canterbury and Otago regions has separated fish populations on a timeframe that allows the fish genomes to retain evidence of the landscape change.

“It’s been really interesting to work with researchers from a completely different discipline and to see how the processes that I’m interested in, mountain building and landscape development, impact on their research and can provide them with an explanation for their observations,” she says.

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