Question

Quadrats are small plots, of uniform shape and size, placed in randomly selected sites for sampling purposes. By counting the number of individuals within each sampling plot, we can see how the density of individuals changes from one part of the habitat to another. Dispersion refers to the evenness of the population's distribution through space. (Dispersion should not be confused with dispersal, which describes movement rather than pattern.) A completely uniform distribution has maximal dispersion, a randomly scattered population has intermediate dispersion, and an aggregated population with clumps of individuals surrounded by empty space has minimal dispersion:

1. If densities are equal, which would yield a higher variance in numbers of individuals per quadrat: a highly aggregated population or a highly dispersed population?

2. Give an animal example of high dispersion; of low dispersion. Give a plant example of high aggregation; of low aggregation.

Answer 1

1. As already mentioned in the paragraph about dispersion and dispersal and in the given scenario where both the quadrants are having similar densities and since is for evenness of species (individuals) in the given are, so variance should not be significant in such condition as compared to later one. Therefore, population that is highly dispersed may exhibit higher variance.
2. Motile or moving animal show higher dispersion as compared to non-motile animals. Some invertebrate show high whereas other invertebrate show low dispersion, in this context, spiders exhibit higher dispersion as compared to other arthropods like insects. In case of plants tropic plants (or rain forest) exhibit high aggregation whereas plant in arid (desert) region show low aggregates due to variable evenness and species richness in the mentioned areas.