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The article said up to 40% of matings were forced, not that 40% of female ducks die from forced matings.
by simulate-me 5y ago
The article said up to 40% of matings were forced, not that 40% of female ducks die from forced matings.
- tomrod 5y agoFair. But even a non-trivial amount dying from forced mating would push evolutionary pressure, right?
- deleted 5y ago[deleted]
- the_af 5y agoI just did a ctrl+F and the article doesn't mention ducks dying at all.
- mxkopy 5y ago>In some cases, the female genital tract prevented the penis from fully inflating, and was full of pockets where sperm went to die. I think this is what they mean. Not offspring dying per se, but still an evolutionary pressure
- mbreese 5y ago> This often leads to a violent struggle, in which males injure or even drown the female. In some species, up to 40 percent of all matings are forced. There is no indication of the rate of drowning, but it would be a constant risk across all females, so no real evolutionary pressure would be evident (aside from a risk to the species as a whole). That is to say: the rate of drowning for females would have to be very low, otherwise the species would fail. If the rate was too high, you’d expect to see a counter pressure to have a higher rate of females born versus males. The point here is that as reproductive structures evolved, the female developed equally complex structures. She might not a choice in if mating occurs, but she does have a choice in whether a particular male fertilizes her eggs. That is the evolutionary pressure… not in response to death from forced mating. > Whatever the females were doing, they were succeeding. In ducks, only 2 to 5 percent of offspring are the result of forced encounters. So regardless of if the mating was forced or not, female ducks are quite successful in choosing who fertilizes her eggs.
- eru 5y agoWhy would it be a constant risk across all females? There would be quite a lot of pressure to not die from forced mating. Can't reproduce when you are dead after all.
- atq2119 5y agoI think their point was that there is no selective pressure on the males to reduce their level of mating violence. From the males' perspective, the situation looks like a prisoners dilemma.
- eru 5y agoWouldn't there be lots and lots of pressure? A male that kills his mate has fewer offspring than a mate that manages to keep the female alive, doesn't he?
- mbreese 5y agoSplit the population of all female ducks into two groups: those that can control the genes passed on to their offspring and those who can’t. From the female perspective, this is the question. Which group will be more successful? The risk of drowning during mating is the same for both groups. So, neither group gets a natural selection advantage from being less likely to drown, because it is a constant risk for both groups. The key here is that the males don’t know if the successfully mated with the female (passed on their genes) or not. Only the female knows.
- deleted 5y ago[deleted]
- ars 5y agoI'm not understanding the selection here - for this to evolve there must be something better about offspring where the female picks the encounter. Seems to be the strongest evolutionary signal would be where the female has lots of offspring, whether desired or not.
- deleted 5y ago[deleted]
- mxkopy 5y agoI think there is an independent pressure towards aggression and physical size, considering the violence inherent in the animal world. So you get multidimensional optimization of a single quantity - become too aggressive and your sperm won't pass, but if you're not aggressive enough you might not eat.
- tomrod 5y agoHey that's a really good point. Thanks!