recap

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54.4 recap

Efforts to manage populations are more likely to be successful if they are based on an understanding of life histories and population and metapopulation dynamics. Biological control is the use of natural enemies to reduce the population density of an economically damaging species. Metapopulations can conserve endangered species if source populations, which supply a source of individuals to sink populations, can rescue those populations from extinction.

learning outcomes

You should be able to:

  • Specify possible density-dependent approaches to controlling a population of undesirable organisms, and discuss the different results each approach would have.

  • Analyze the importance of source and sink populations in a metapopulation in terms of their function in conserving a species from extinction.

Question 1

Describe an effective strategy for recovering the population size of a desirable species that has a K-strategist life history.

Species that have a K-strategist life history live longer, reproduce at a larger size, and produce fewer offspring over a longer period of time compared to r-strategists. As a result, recovery may require managing the number or size of the individuals within the population so that they live long enough, and/or reach a large enough size, to successfully reproduce at a rate that increases their population size over time.

Question 2

Refer to Figure 54.17.

  1. Describe factors responsible for the metapopulation size of the Edith’s checkerspot butterfly in the San Francisco Bay area.

  2. Given the 1998 extinction of the Morgan Hill population, what is the likely fate of the metapopulation? Explain your answer.

a. Some factors that affect the metapopulation size of the Edith’s checkerspot butterfly in the San Francisco Bay area include the number and size of serpentine rock outcrops with the host plants of the butterfly, the effects of climate on the populations, the dispersal rates between the populations, and the number of source and sink populations.

b. With the extinction of the Morgan Hill population, the metapopulation faces likely extinction. Large populations, such as Morgan Hill, serve as sources that recolonize smaller populations after temporary local extinctions. Without such source populations, continuation of the metapopulation over the long term is much less likely.