Comment by VWWHFSfQ
7 months ago
> species that evolve with a predator tend to reproduce more quickly
As an example of this, a healthy female rabbit will produce anywhere from 20 to 50 additional rabbits in a single year. There have been many documented explosions of rabbit populations due to lack of natural predators which have caused significant ecological crisis.
They've evolved to reproduce so quickly because they are the "food" in the food chain. Without the predators above them, they will _eventually_ stop reproducing so quickly because they are only killing themselves by doing so.
It's worth puzzling about the mechanisms that would lead a fast reproducing species to slow down...
My best guess is that internal competition for scarce resources leads to territoriality, which in turn might select for better resource utilization. Including reduced reproduction, which creates more resource competition. But this doesn't feel super obvious.
Otherwise, we have plague and starvation acting as stand ins for apex predators, which isn't much fun... And apparently isn't generally enough to reduce environmental externalities from over population.
The term of art for everything that includes those factors is "carrying capacity" [0].
It's not as much that the fertility necessarily drops, but that under some conditions the death rate equals or overtakes the birth rate.
And the system is dynamic. So conditions changes, as in some of your examples, even just because the population grows. EG scarcer resources.
[0] https://en.wikipedia.org/wiki/Carrying_capacity
That is not necessarily the case. Certainly, overpopulation can cause die-offs…
However, species don’t evolve as a unit. Which genomes are most likely to survive a die-off?
All else being equal?
The ones with the most copies. So not the ones that are holding back on reproductions.
What causes them to stop reproducing is the destruction of their natural environment on which they feed on. Which is what you want to avoid.