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By Stephen Luntz

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Multiple Sex Selection Strategies in Skinks
A species of Tasmanian lizard has evolved two separate mechanisms for choosing the sex of its offspring: one for high altitudes and one for sea level.

Snow skinks live in both the alpine and coastal regions of Tasmania. Studies of the coastal population concluded that they used temperature-dependent sex determination (TSD), a system common in reptiles. Females that basked in warm weather early in pregnancy produced mainly daughters, while those with fewer opportunities to sun themselves had sons.

This makes evolutionary sense. Larger females produce more offspring, so there is a benefit being born early in the breeding season in order to have grown more when it comes to mating time. But body size at breeding time does not confer an advantage for male skinks, which has led researchers to conclude that they don’t fight for mates.

However, an international team including Dr Erik Wapstra of the University of Tasmania found that skinks living in subalpine mountain areas behaved differently. Here mothers produced equal numbers of sons and daughters irrespective of the temperature conditions they were exposed to. High altitude skinks grow more slowly than their lowland cousins and take several years before they are ready to breed, by which time the benefits of a few extra weeks of life are...

The full text of this article can be purchased from Informit.