member is offline
Creatures in Australia clone themselves
« Thread started on: Dec 11th, 2003, 5:00pm »
By Bob Beale
December 12, 2003
Is it the scratchy sand? Does the glare induce headaches? Is it the heat and the flies?
Whatever the reason, scientists have discovered many creatures living in Australia's harsh arid zone are giving males the flick and opting for all-female communities that reproduce by cloning themselves.
In a new research paper titled "Why is sex so npopular in the Australian desert?", a Sydney University doctoral student, Michael Kearney, details a swag of bizarre reptiles, insects and even that classic tough outback tree the mulga as species that have given blokes the heave-ho.
How they reproduce - by parthenogenesis, or virgin birth - is one thing, but why they do it, and where, has researchers baffled.
Asexual reproduction - so rare that less than one species in 1000 practises it - tends to occur in extreme or fringe environments, such as high altitudes,
high latitudes, deserts and places disturbed by fires and droughts.
Mr Kearney unearthed some discoveries by the distinguished geneticist Michael White, who died before he could publish his findings that two Australian
insects - a wingless grasshopper and a stick insect - reproduce asexually. Both insects occur in the same region of Western Australia and feed on the same
species of mulga trees and senna shrubs, plants that are now known to be prone to self-cloning.
"Your instinct tells you it can't be coincidental that so many lineages are all doing the same extraordinary thing here," says Rick Shine, the evolutionary
biologist who is supervising Mr Kearney's research.
"Presumably there's some reason to kick boys out of the arid zone."
The latest example is a type of Menetia skink recently identified in southern central Australia. It is the first parthenogenetic species found anywhere in the world for 20 years.
The last one was another Australian lizard, Bynoe's gecko.
That gecko compounds the mystery because the asexual type is often found alongside others of the same species that reproduce sexually.
The trouble with males, Professor Shine points out, is that they cannot reproduce themselves independently, they consume scarce food and they perpetuate
maleness in a population through sex.
Females invest heavily in creating eggs, hereas "males are just coming along as parasites and throwing their genes into the mix".
So if self-cloning is so much more efficient, why did 99.9 per cent of species choose sex?
A popular theory is the Red Queen hypothesis, named after the Lewis Carroll character who tells Alice that she must keep running simply to stay in the same place.
The big advantage of sex, that theory suggests, is that it creates genetic difference between individuals, driving evolutionary competition. Offspring differ slightly from their parents and from each other, with some better suited than others to adapt to new circumstances.
Bynoe's gecko may be living proof - the clones have a higher deformity rate, and where the asexual and sexual types are found together the clones suffer
heavier infestations of parasitic mites.
Mr Kearney says he used that example to explain the Red Queen hypothesis to a bemused outback station owner.
"He replied, with a sardonic grin: 'So if we stop having sex we will end up with lots of little red mites all over our faces?' "