Aussie Finch Forum

I watched the FSA video by the genetics man on long-tailed grassfinches. He showed recent work in sequencing Heck's and yellow-billed long-tails' DNA.

There appear to be major chromosomal (DNA) differences between the two types especially in the sex chromosomes.

This got me wondering:

1. If such profound differences are found in such seemingly similar species, then what dramatic damage are we doing to species when we cross them either to "save" a species or to transfer mutations????

On the other hand....

2. If such profound differences in DNA are shown between such closely-related species, then are we perhaps overemphasising the importance of genetic purity. Perhaps the underlying DNA is not so important since it has such a small overall effect on a bird's outward details (colour, behaviour etc).

It's a real "egg-head" topic, I suppose but I'd be interested in other people's thoughts. I tend towards the first line of thought,myself. I would be keen to see results of say white Heck's or fawn longtails compared to wildtype genome sequences.

Tom

The only instances I know where people have crossed to "save" rare species has always resulted in accelerating the demise of those species as those other breeders who may be otherwise interested in breeding pure ones to preserve them lose all interest when hybrids proliferate their captive stocks. A recent example of this is my giving up on trying to help with Javan Munias where birds are displaying Bengalese habits and producing fawn & pied offspring. More than happy to breed up species with dwindling stocks but not prepared to give breeding aviary space to hybrids under any circumstances.
If the white & fawn Hecks were established using pure Hecks base stock, their genome should only differ in terms of the white/fawn colour genes (IMO).

[quote="Uraeginthus"]I watched the FSA video by the genetics man on long-tailed grassfinches. He showed recent work in sequencing Heck's and yellow-billed long-tails' DNA.

There appear to be major chromosomal (DNA) differences between the two types especially in the sex chromosomes.

This got me wondering:

1. If such profound differences are found in such seemingly similar species, then what dramatic damage are we doing to species when we cross them either to "save" a species or to transfer mutations????

On the other hand....

2. If such profound differences in DNA are shown between such closely-related species, then are we perhaps overemphasising the importance of genetic purity. Perhaps the underlying DNA is not so important since it has such a small overall effect on a bird's outward details (colour, behaviour etc).


What the speaker was saying is probably/is right of the differences of the two as one was of the far West and the other of East of topend Australia.Population of both now cross over in the central North and cross breeding of the Hecks and Yellow billed longtails in the wild now produce different shades of orange coloured billed birds.This is a natural occurrance in the wild and imo,in the years to come,one will cancel out the other and we will see only orange billed birds in the wild but in saying that there are some breeders with some really good red billed hecks in captivity so the strain will survive with no inter breeding of the two in our aviaries so there separate DNA should survive.
White hecks were blown into this country by stong winds but fawn longtails appeared in our own aviaries and probably exist in the wild as their colour change isn't so dramatic as a white bird due to predation.
The white hecks is the bird responsible for white/cream parsons as breeders transferred the mutation as a fertile hybrid between the two to a point where the white parson is 15/16 parson but will always be a hybrid with its DNA. Craig

It's a real "egg-head" topic,

You cannot maintain multiple generations within captivity without changing that strain's genetics.

Let me start with this statement, which may prove to be a bit controversial, and then work back to Tom's comments.
I watched Simon's lecture again and he highlighted the differences between Zebra finches held in captivity for many generations and those in the wild (not only appearance but also behaviour). These differences are genetically mediated, not just environmental. The very process of breeding birds in captivity changes the selection pressure they are under, so factors like foraging ability and predator avoidance become less important. Birds that are prolific breeders under a wide range of circumstances are favored and increase in numbers.

The genetics of the population of birds that you start with and those of the birds after 10 generations of captive breeding is different, the birds have changed.

The reason that these changes can take place, and in such a short time, flows from the genetic variability of the initial population. These birds may all look the same, but they are not. There will be subtle differences between the individuals, both in appearance, behaviour and physiology. The vast majority of these difference will not be obvious, think of human blood groups which can be A, AB, B or O and +ve rhesus or -ve rhesus, but can impact on the success of that bird in subtle ways. No two birds will have exactly the same DNA, even if they are from the same species.

So back to Tom's point about the genetic variation between subspecies (Long tails and Hecks) and the importance or otherwise of mutations.
I suspect if Simon had shown a graph that demonstrated the differences in DNA WITH-IN either the Long tails or the Hecks, it would have shown significant differences.
You would expect these differences to be even greater between the two subspecies.
Most mutations are single point mutations, affecting just a single gene in a particular way. These would be just one more difference (although a very obvious one).

1. If such profound differences are found in such seemingly similar species, then what dramatic damage are we doing to species when we cross them either to "save" a species or to transfer mutations????

On the other hand....

Personally I don't see any justification for this.

2. If such profound differences in DNA are shown between such closely-related species, then are we perhaps overemphasising the importance of genetic purity. Perhaps the underlying DNA is not so important since it has such a small overall effect on a bird's outward details (colour, behaviour etc).

I think this depends on what you mean by genetic purity and why you feel it is important. As stated above, it is my view that the very action of breeding birds in captivity changes their genetics, as such they are no longer "pure". The vast majority of differences are invisible and as such the aviculturalist is unaware of them. We tend to focus and get excited about the relatively small number of "visible" changes that we refer to as mutations (although you could argue that all the invisible changes are mutations as well).
From reading this you might feel it is all a bit "doom and gloom" and that I believe that the indiscriminate breeding of mutations is of no consequence.
This is not the case, and my personal opinion is that we should continue to breed strains which are as close to wild type as we can, but recognize the limitations.

Cheers
Brett

Yes it is an egg-head topic, and I love it

From egghead to ditto
There will naturally be dna variation in wild population sof pure species but the blackheart and Hecks, when compared as two speparate groups, show consistent dna differences (as I read it). I realise there is now a hybrid zone for these two varieties (which also occurs with other avicultural species such as twenty-eights and Port Lincolns) so the dna is now mixed where once they were not.This may be happening to white-bellied bloods on Cape York.

Changes to dna due to domestication, I would imagine, would centre around decreased genetic diversity but with some traits becoming more common. Let's assume that keeping our stock as close to wildtype as possible will also preserve the wildtype genes, and that a mutation such as fawn or slate in a blackheart is only a point mutation when viewed as part of the overall genome. Crossing species to transfer that mutation would run counter to the original idea that we should preserve the original genome as much as possible.

BUT if domestic versus wildtype genomes are so different while the phenotypes are the same, are we placing too much emphasis on keeping species pure? Is it really a problem crossing say, red-collared and scaly-breasted lorikeets as long as the birds look like the species we expect them to represent??

By the way, I am not familiar with the zebra finch comparisons. Was this some of Richard Zann's work? I'd be interested to know if the changes have occurred across the genome or concetrated in clusters on particular chromosomes.

Uraeginthus wrote:From egghead to ditto
so the dna is now mixed where once they were not.This may be happening to white-bellied bloods on Cape York.

Hi Tom,regarding your comment on WB bloods.Sadly i have been talking to a few guys who have been searching the two areas (Laura and Lakefield National Park)on Cape York in the last couple of years photographing birds and are finding three birds out of five are carrying grey or black in their under bellies.It looks like the BB crimsons have invaded their territory and are hybridizing to produce these birds.
I am also finding with my own birds,two pr in particular that are not related to my original strain are now throwing light grey bellied birds yet last year they produced snow white bellied birds,which leads me to the question is it genetic,diet,weather or the environment and as far as i know they haven't had BB blood in them.
Craig

three birds out of five are carrying grey or black in their under bellies.
How does anyone know these birds are crosses? Have they done genetic checks? Or could it just be a mutation that is working to the birds benefit, so is increasing? As beneficial mutations do in nature?
LML