Hi all
This is perhaps related to the thread about ancestral species. We sometimes read about a species being brought back from the brink of extinction with a very low number of individuals left. And we also often read about genetic isolation and inbreeding. For example, Wingspan recently published an article about the Mission Beach cassowaries referring to threats such as habitat loss and road-kill but not referring at all to genetic inbreeding. Yet, I have heard from a number of sources that the main threat to the MB birds (who have access to banana and paw paw plantations for feeding – I have seen them doing this) is the likelihood of inbreeding through their genetic isolation.
Nick L recently saw the Albert lyrebirds on Mt Tamborine – I have heard that that population is doomed due to its genetic isolation.
So where does the truth lie? Perhaps some of our scientific members might have some comments? When does inbreeding and genetic isolation become a concern? Or can a population always come back from a very low bank of individuals?
Cheers
Andrew
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Sadly, the situation with Albert’s on Tamborine Mountain is more serious than just inbreeding. Their habitat has been fragmented by human settlement.
Although the Parks Service in its wisdom (or lack of? Deviousness?) refers to a Tamborine Mountain N P, there are in fact a number of small discrete reserves. Witches’ Falls, The Knoll, Joalah, Macdonald, and Palm Grove, all have Albert’s but they are separated by what is effectively suburban residential development.
South from Palm Grove N P, there is an area below the scarp opposite Hartley Road and running south, that has Albert’s. And another area below the scarp immediately north of St Bernard’s Hotel (in Mount Tamborine village), also with Albert’s. And finally the Australian Army’s Canungra Jungle Training Area, running south from Mt Tamborine to Beechmont has several Albert’s areas.
In at least three places on Tamborine Mountain, Albert’s have taken to foraging in gardens adjoining their habitat. So maybe, just maybe, they will overcome their distrust of humans to the extent of being able to move between at least some of those tiny areas of habitat. If so, the population just might survive long enough for inbreeding to be a problem, and introduction from another area, to be worth trying.
At least initially however, I suggest that it would be preferable not to introduce birds from elsewhere; that it would be sufficient to move one or a few from just over the scarp at Mt Tamborine to say Witches’ Falls and Palm Grove. And the reverse. Can’t see it happening, however.
Cheers
Syd
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I would have thought that with species with sub-populations in danger of inbreeding it would be relatively easy to capture individuals from larger populations and introduce them into the smaller ones occasionally to maintain diversity. For example you might capture an Albert’s in the Border Ranges and release it on Tambourine.
John Leonard
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Hi Andrew,
It’s not so much a problem for a lot of other species as they have quite a range of genetic diversity within their populations, so you can get to a fairly small number of individuals and not end up with them being called Cleetus and playing banjoes (what is the plural of banjo?). However, if a species has been reduced to a very small number a few times previously, it tends to wipe out that diversity – we can see that in humans and domestic cats, both of which were probably reduced to around a couple of thousand at a few points in history. Even then, with a limited genetic stock (it’s often been said that one troop of chimpanzees has more diversity within it than the entire human race), it would take only 32 individuals (and very careful management of who was breeding with who for a few generations) to ensure that serious genetic problems don’t occur. However, I don’t know the background of the species you mention, so I couldn’t help on that… Cheers,
Tony