FREEZING POLAR OCEANS— A GREAT PLACE FOR FISH SPECIES FORMATION
THE BURNING QUESTION— THE EFFECT OF TORPOR ON MAMMALS DURING AND AFTER BUSHFIRES Although several ecological studies have examined animal diversity and abundance before and after bushfires, the reasons why some species perform better than others have remained obscure. Funded through the ARC Discovery Projects scheme, Professor Fritz Geiser, ARC Discovery Early Career Researcher Award (DECRA) recipient, Dr Clare Stawski, and their research team at the University of New England, have studied how small mammals, which have high rates of energy expenditure and food requirements, can survive bushfires and post-fire conditions. Many mammals lower their body temperatures during a state of daily torpor or multiday torpor (hibernation) as an energy preserving mechanism to survive harsh conditions, like winter, or as a response to unpredictable events such as drought. Torpor may reduce energy use by up to 99%, but is risky during bushfires because torpid animals may not be able to rewarm in time to escape the fire, especially during ‘hazard reduction’ burns, which are lit in winter when animals are more likely to be hibernating. The researchers have discovered that despite these risks, torpor does provide some species with an adaptive advantage compared to animals which have constant high body temperatures. Torpid mammals can respond to smoke and using torpor substantially reduces foraging requirements and therefore exposure to predators. Overall, the findings linked expression of mammalian torpor with a lower risk of extinction.
A study involving researchers at the ARC Centre of Excellence for Coral Reef Studies (based at James Cook University) and the University of Michigan— including ARC Discovery Early Career Researcher Award (DECRA) recipient, Dr Peter Cowman—has analysed the evolutionary relationships between fish species and found that the fastest rates of species formation have occurred at the highest latitudes and in the coldest ocean waters.
The researchers examined the relationship between latitude, species richness and the rate of new species formation among marine fishes by assembling a time-calibrated ‘evolutionary tree’ of all 31,526 ray-finned fish species, then focused their analysis on marine species worldwide. They found that the fastest rates of new species formation occurred in Antarctic icefish and their relatives. Other temperate and polar groups with exceptionally high speciation rates include snailfish, eelpouts and rockfish. The results are surprising considering the adaptions fish like the icefish require to live in the coldest Antarctic waters, and challenge the widely-held idea that the tropics serve as an evolutionary cradle for marine fish diversity.
Exploring the survival of animals during wildfire and fire management burns demonstrated how animals can cope in a post-fire environment where food and shelter are often reduced, and the pressure from predators is increased.
Over the past several million years, cool-water and polar ocean fishes formed new species twice as fast as the average species of tropical fish.
A survivor of the wildfire, a common dunnart, Sminthopsis murina, with pouch young in spring 2013. This species uses daily torpor. Credit: Fritz Geiser.
ADVANCING ENVIRONMENTAL SCIENCE AND MANAGEMENT 44
ADVANCING ENVIRONMENTAL SCIENCE AND MANAGEMENT 45
Icefish uk. Credit: Wikipedia commons.
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