K-selected vs. r-selected Species

K-selected Species

K-selected species are those whose life history strategies are optimized for living at or near the carrying capacity ($K$) of their environment. They thrive in stable, predictable environments where competition for resources is high. Their strategy is to invest heavily in a small number of offspring to ensure their survival and competitive success.

Key Characteristics of K-selected Species:

• Reproduction: They typically breed many times throughout their lifetime (iteroparity).
• Offspring: They produce a small number of large-sized offspring.
• Parental Care: They provide significant parental care to their young, which increases the likelihood of survival.
• Lifespan: They generally have longer lifespans and mature later.

Examples include most birds and mammals, such as elephants, humans, and whales. These organisms have evolved to be efficient competitors, but they are also more vulnerable to environmental changes or habitat destruction due to their lower reproductive rates.

r-selected Species

r-selected species are those whose life history strategies are optimized for a high population growth rate ($r$). They are adapted to thrive in unstable, unpredictable environments and are excellent colonizers of new habitats. Their strategy is to produce a large number of offspring, accepting that most will not survive, but ensuring that a few will reach maturity.

Key Characteristics of r-selected Species:

• Reproduction: They often breed only once in their lifetime (semelparity).
• Offspring: They produce a large number of small-sized offspring.
• Parental Care: They provide little to no parental care.
• Lifespan: They have shorter lifespans and mature very quickly.

Examples include the Pacific salmon fish and bamboo, which breed once and then die. Other examples are oysters and pelagic fishes, which release millions of tiny eggs with no parental investment. This strategy works well in environments with high mortality rates for young but can lead to boom-and-bust population cycles.