Rate of Evolution
Recent geological studies have revealed dramatic evolutionary histories for many South Island river systems. These histories include river reversal and river capture events— driven by tectonics and glaciation. Each of these geological changes has physically isolated populations of freshwater fish that were previously connected (vicariance). These events can be used to determine time-scales of evolution.
- Geological dates and evolutionary rates: using river vicariance to pinpoint the pace of molecular change
River flow directions and river drainage systems are not necessarily permanent features of the landscape. Geological changes can cause a river to flow in a different direction, and become a tributary of a different drainage system. This river capture process has been common in the South Island of New Zealand over the past few million years.
Path of the Taieri River
The Taieri River drains only the eastern Otago uplands, and follows an almost circular path from its source to the sea. The Taieri River discharges to the Pacific Ocean at Taieri Mouth, only 60 km from its source area in the Lammermoor and Lammerlaw Ranges.
Sutton Salt Lake
The Sutton Salt Lake is the only saline lake in New Zealand, and has formed in a windy cool-temperate maritime climate. Consequently, the lake is distinctly different from most of the world's saline lakes that form in arid continental settings.
Evaporative salts in Otago
The combination of high temperatures, low rainfall, and wind-driven evaporation has resulted in localised accumulation of evaporative salts in inland Otago, and Central Otago in particular.