It’s not so much the different types in themselves that prevent competition, but having multiple types make it possible to have a mechanism that forces all organelles to come from only one pre-selected parent. If all organelles come from the female, then a rogue mitochondria cannot take over by making more copies of itself or by poisoning other mitochondria, because the only way to make it to the next generation is to be in the female gamete, period. In other words, there’s not much an organelle can do to increase in frequency, aside from improving the overall fitness of the organism. Does that make more sense?
I would guess that when organelles are inherited from both parents, the traitor organelle is disadvantaged by its burden on the host, but advantaged by it’s ability to be the predominant organelle in the offspring. If the cost-benefit is favourable, then the traitor organelle will take over. OTOH, if only one parent transmits the organelle, the advantage disappears but the burden remains. So I’d expect that it makes it more difficult for traitor mitochondria to invade. Hopefully that makes sense!
It’s not so much the different types in themselves that prevent competition, but having multiple types make it possible to have a mechanism that forces all organelles to come from only one pre-selected parent. If all organelles come from the female, then a rogue mitochondria cannot take over by making more copies of itself or by poisoning other mitochondria, because the only way to make it to the next generation is to be in the female gamete, period. In other words, there’s not much an organelle can do to increase in frequency, aside from improving the overall fitness of the organism. Does that make more sense?
But by making more copies of itself/poisoning other mitochondria isn’t it more likely to end up in the female gamete?
Not quite, if it’s less efficient at doing the normal mitochondria work, it puts a big burden on the cell, who is then less likely to reproduce.
But wouldn’t that be the case for any organelle, even one which is inherited from both parents?
I would guess that when organelles are inherited from both parents, the traitor organelle is disadvantaged by its burden on the host, but advantaged by it’s ability to be the predominant organelle in the offspring. If the cost-benefit is favourable, then the traitor organelle will take over. OTOH, if only one parent transmits the organelle, the advantage disappears but the burden remains. So I’d expect that it makes it more difficult for traitor mitochondria to invade. Hopefully that makes sense!