Problem 1
Fire ants have spread from Brazil north through Central America and Mexico into the southern United States, and they continue to spread north. Discuss how you might determine the potential geographical range of this pest species. Korzukhin et al. (2001) discuss the problem.
Problem 3
Cain (1944) stated: Physiological processes are multi-conditioned. and an investigation of the effects of variation of a single factor, when all others are controlled, cannot be applied directly to an interpretation of the role of that factor in nature. It is impossible, then, to speak of a single condition of a factor as being the cause of an observed effect in an organism. Discuss the implications of this principle-that the factors of the environment act collectively and simultaneously-with regard to methods for studying species distributions.
Problem 6
Hutchins (1947) set out a simple but elegant hypothesis that the geographic limits of marine species are set by thermal tolerances of the most sensitive life history stage. Thus species are limited by intolerance to cold at the poleward limit and by intolerance of heat at their equatorial limit. Discuss what factors might invalidate this hypothesis. Wethey (2002) discussed this issue for barnacles.
Problem 7
The British barnacle Elminius modestus extends higher on the shore in the intertidal zone than does the barnacle Semibalamus balanoides when the two species occur together. However, these two species have similar tolerances to desiccation, salinity, and temperature. The range of initial settlement of young barnacles is the same for the two species. Given these facts, can you suggest an explanation for the observation that \(E .\) modestus extends higher on the shore than \(S\). balanoides?
