Parthenogenesis in condors

[CharonY]

While it is not entirely unknown in birds, it is still interesting to see examples. As in this case, Californian Condors were found to reproduce without input from males, though one was present.

Quote

Parthenogenesis is a relatively rare event in birds, documented in unfertilized eggs from columbid, galliform, and passerine females with no access to males. In the critically endangered California condor, parentage analysis conducted utilizing polymorphic microsatellite loci has identified two instances of parthenogenetic development from the eggs of two females in the captive breeding program, each continuously housed with a reproductively capable male with whom they had produced offspring. Paternal genetic contribution to the two chicks was excluded. Both parthenotes possessed the expected male ZZ sex chromosomes and were homozygous for all evaluated markers inherited from their dams. These findings represent the first molecular marker-based identification of facultative parthenogenesis in an avian species, notably of females in regular contact with fertile males, and add to the phylogenetic breadth of vertebrate taxa documented to have reproduced via asexual reproduction.

https://academic.oup.com/jhered/advance-article/doi/10.1093/jhered/esab052/6412509

 

[Phi for All]

The paper seems to suggest this may be more common in birds than previously thought. I get the genetic stability benefits, and it's always advantageous to lay more eggs, but doesn't this create a lack of genetic diversity if it happens more often?

Quote

We believe that this is the first study to use molecular markers to identify facultative parthenogenesis in an avian species. This novel finding in California condor females housed with fertile males raises the question of unrecognized parthenogenesis in other avian species (Fields et al. 2015).

 

[StringJunky]

1 hour ago, Phi for All said:

The paper seems to suggest this may be more common in birds than previously thought. I get the genetic stability benefits, and it's always advantageous to lay more eggs, but doesn't this create a lack of genetic diversity if it happens more often?

 

Maybe that's a species-survival insurance mechanism when the chips are down, at the expense of variation.

Edited November 3, 2021 by StringJunky

[CharonY]

7 minutes ago, StringJunky said:

Maybe that's a species-survival insurance mechanism when the chips are down, at the expense of variation.

In other species it seems to be related to that. Parthenogenesis is often observed if few or no male partners are found as well as under certain stress conditions. But overall it does not seem to be the favoured mode of reproduction, otherwise it would be far more common (which could be related to loss of genetic diversity).

[mistermack]

It's particularly interesting, if the chicks were males. The extract seems to indicate that, so the chicks were not simple clones. 

It has some logic to it, in survival terms, for a species that has been rare for a very long time. Individuals that can't reproduce without a successful mating are less likely to pass on their genes, in the long term, than those that can produce viable young in this manner. The element of competition becomes secondary under conditions of scarcity of a mate. Just producing any kind of fertile sucessor before you die would be an advantage to your genes, and give them some chance of being passed on.

So Condors could have evolved this tendency through being rare, over millenia, and it shows up now, even though a mate is available.

[bangstrom]

A study was done in the SW USA on blue tail lizards whose only reproduction is by parthenogenesis since there are no males. The lizards are numerous and surprisingly genetically diverse. Somehow, they also overcame the diversity problem.

I once worked in a laboratory that only ordered female rabbits from a supplier and it was not unusual to find a pregnant rabbit among the orders. I often wondered if parthenogenesis is possible among rabbits. And how about humans? There is no lack of claimants for a study.

[mistermack]

On 11/12/2021 at 6:29 AM, bangstrom said:

And how about humans? There is no lack of claimants for a study.

The only one I can think of is baby jesus.