What conditions favor semelparity over iteroparity?

Semelparity is a reproductive strategy where an organism reproduces only once and then typically dies after reproduction. Examples of semelparous species include some insects, salmon, and annual plants. On the other hand, iteroparity is a reproductive strategy where an organism reproduces multiple times over the course of their lifetime. Examples of iteroparous species are humans, most mammals, and perennial plants.

There are several factors that can favor semelparity over iteroparity, which include: 1. High mortality rates: In environments where the chance of an organism surviving to reproduce multiple times is very low, semelparity may be favored. This is because in such environments, investing all of the organism's resources into a single, large reproductive effort may increase the probability of reproductive success. 2. Unpredictable environments: In habitats where resources are scarce or unpredictable, semelparity may be favored because it allows an organism to invest all available resources into reproduction when conditions are favorable. 3. Low adult survival rates: If the adult survival rate is low, organisms may be better off investing all their resources into a single, large reproductive event instead of spreading resources across multiple reproductive events. 4. High fecundity: Semelparous species generally produce a large number of offspring in a single reproductive event. This can be advantageous in environments where the survival rate of offspring is low, as it increases the likelihood that at least some offspring will survive to adulthood.

In conclusion, semelparity may be favored over iteroparity in environments with high mortality rates, unpredictable resource availability, low adult survival rates, and low offspring survival rates. Organisms that live in these types of environments may benefit from investing all of their resources into a single, large reproductive event as opposed to spreading their resources across multiple reproductive events throughout their lifetime. This allows them to increase their chances of reproductive success and ensure the survival of their genetic material.