leucistic Crimson Rosella

[Philip Veerman <>]

Ryu,

Yes. You have listed the normal features of recessive trait inheritance. So assuming the website is correct and the birds are displaying that particular feature, all that holds.  I would not think that leucistic is the right term. However I suggest slight rewording to the following:

• A bird may carry the mutated gene but not show it.
• In this case the “mutant” gene exists at low levels in the population. So most birds do not show or carry the “mutant” gene.
• The 'blue' Rosella must have received the mutant gene from both parents.
• 2 normal parents both carrying the recessive gene: on average, all other things being equal, 25% of their offspring will show the 'blue' character, other 75% normal.
• 1 blue rosella and the other normal parent carrying the recessive gene: on average, all other things being equal, 50% of their offspring will show the 'blue' character, other half normal.
• 1 blue rosella and the other normal parent that is not carrying the recessive gene will only produce normal looking offspring. Although all them will carry the mutant and the normal gene.
• 2 blue rosella parents: all of any offspring will show the 'blue' character.

To explain why: for example “25% chance of 'blue' offspring” of the heterozygous couple, only applies in regard to just each one offspring..... For example, if they end up having 20 + offspring, there is a vastly higher chance than 25% of them of having at least one 'blue' offspring – on average 5 out of 20.......

 

There also can be all sorts of other factors that can influence these pure genetic ratios up or down.

 

As for Sue’s other question, I’d guess 19 years is quite feasible for a wild rosella, but it is more likely not to be the same bird but could well be related. “First saw one” suggests to me there is more than one, a little ongoing population there that carry the gene and rarely is shown.  

 

Philip

 

 

 

From: Ryu Callaway [ Sent: Sunday, 5 November, 2017 10:45 PM To: Sue Lashko; canberrabirds chatline    Subject: Re: [canberrabirds] leucistic Crimson Rosella

 

And a similar bird reported to Canberra Nature Map in September from Banks

http://canberra.naturemapr.org/Community/Sighting/3380520

 

The following site (http://users.skynet.be/platycercus/CrimsonMut.html) lists the 'blue' Crimson Rosella which looks like these birds as a recessive mutation. 

My simplistic interpretation of that I think is:

• A bird may carry the mutated gene but not show it
• For a Crimson to be 'blue' both its parents must carry the mutant gene
• 2 normal parents both carrying the recessive gene: 25% chance of 'blue' offspring
• 1 blue rosella and the other normal parent carrying the recessive gene: 50% chance of 'blue' offspring
• 2 blue rosellas: 100% chance of 'blue' offspring

Ryu