Mountains Moving and Building Increase Fish Diversity in NZ

The formation and growth of mountain ranges can separate biological populations and create newly evolved species over time. The mountain ranges of New Zealand's South Island have done just that with its freshwater fish, according to a new study published in Nature Geoscience.

Finding a direct link between altering topography and biodiversity has proven difficult for scientists because other environmental and ecological factors usually play a role in speciation. However, Geology Professor Dave Craw, and Zoologists Graham Wallis and Jonathan Waters of the University of Otago in New Zealand concentrated on South Island, where 18 freshwater species of fish evolved in direct correlation with the movement of the surrounding tectonic plates-indicating a straightforward association between the two changes.

"By modelling the mountain-building processes, we can really start to understand how the changing landscape has shaped biological processes, Craw said in a release. "New Zealand's geographic isolation and dynamic geology make it the perfect place for understanding evolution."

The Otago researchers alongside scientists from GNS Science and the University of Tasmania analyzed the topographic evolution of South Island over 25 million years. They found that the island evolved in six tectonic zones that each have a drainage catchment that separated the populations of fish. The scientists studied the projected evolutionary tree of the freshwater fish species from the distinct drainage basins. They analyzed 1,000 fish specimens from more than 400 different locations to demonstrate that fish genomes do in fact retain evidence of the shifting tectonic plates. The results of the study indicated that there was a clear relationship between the divergence in DNA sequences and geological age.

"One particularly interesting thing about the study, from a biological point of view, is that we find such similar evolutionary patterns in unrelated groups of fish species, which really highlights the important role of geology," Professor Waters said in a statement.

Waters and Craw have been working on the association between geology and genetics for nearly 15 years.

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