Overview
This lecture covers the differences between K-selected and r-selected reproductive strategies, their implications for population dynamics, and their influence on species' vulnerability to environmental change and invasiveness.
K-Selected Species (Quality Approach)
- K-selected species produce few offspring and invest significant energy in parental care.
- These species are typically larger and live longer (e.g., elephants).
- They reach sexual maturity slowly and reproduce multiple times over their lifespan.
- K-selected species have a low biotic potential (maximum reproductive rate).
- Their populations grow slowly and are stable, existing near the carrying capacity.
- They are vulnerable to extinction and slow to recover from disturbances.
r-Selected Species (Quantity Approach)
- r-selected species produce many offspring with little to no parental care.
- These species are generally small, short-lived organisms like insects and fish.
- They reach sexual maturity quickly and often reproduce only once.
- r-selected species have a high biotic potential and rapid population growth.
- Their populations are highly variable and can increase or decrease dramatically.
- They are more likely to become invasive due to rapid reproduction and adaptability.
Spectrum of Strategies
- Most species exist on a spectrum between r-selected and K-selected, not fitting perfectly into one category.
- Some species (e.g., frogs, hares) show mixed traits, providing moderate parental care and producing a moderate number of offspring.
Invasiveness and Disturbance
- K-selected species are slow to recover from environmental changes or disturbances.
- Loss of a parent often means loss of dependent offspring in K-selected species.
- r-selected (invasive) species can quickly colonize and outcompete K-selected species due to rapid population growth.
- K-selected species have less genetic diversity and adaptability, making them more prone to extinction.
Practice Skills
- Be able to identify characteristics that make r-selected species more likely to become successful invasives.
- Practice describing data trends, such as relationships between competing species populations.
Key Terms & Definitions
- K-selected species — Species that emphasize parental care and produce few offspring.
- r-selected species — Species that produce many offspring with little to no parental care.
- Biotic potential — The maximum reproductive rate of a population.
- Carrying capacity — The maximum population size an environment can support.
Action Items / Next Steps
- Identify a trait in r-selected species that increases their invasiveness.
- Analyze population data for zebra mussels and unionid mussels in the Hudson River.