Problem 2
How can natural selection maintain the particular ovipositing dance of Anopheles culicifacies, for example, if it results in suitable habitats being left unoccupied? Does natural selection always favor the broadest possible habitat range for a species?
Problem 3
One of the recurrent themes in studying introduced species is that introductions are more successful when more individuals are released (Green \(1997 ;\) Forsyth et al. 2004 ). Are there cases of successful introductions by humans when only a few individuals were released? What might account for this pattern?
Problem 6
English yew (Taxus baccata) is an evergreen tree with an average life span of 500 years (Hulme 1996 ). The regeneration potential of local sites will determine the future distribution of this tree, and seed predators, seedling herbivores, or suitable microsites for germination and growth are the three factors that may limit yew distribution on a local scale. Discuss what observations could distinguish between biotic limitation and abiotic microsite limitation of yew distributions.
Problem 7
At Point Pelee National Park in Ontario, frog surveys showed that the bullfrog (Rana catesbeiana) disappeared in \(1990,\) and from 1990 to 1994 the green frog ( Rana clamitans ) has increased in numbers fourfold (Hecnar and M'Closkey 1997 ). Suggest three possible interpretations for these natural history observations, and indicate how you would test these hypotheses experimentally
Problem 8
Norwegian lemmings do not live in lowland forests in Scandinavia even though they are regularly seen in these areas when their alpine populations are at high density. Suggest three hypotheses to explain the failure of lemmings to establish permanent populations in lowland forest, and discuss experiments to test these ideas. Oksanen and Oksanen (1992) discuss this question.
Problem 9
Laboratory tests for allelopathy have been criticized because the chemicals that act in the laboratory may not be effective in the field. Could this criticism be blunted by doing field experiments? Do you think that plants might evolve to produce chemical exudates that are not effective in the field?
Problem 10
Laboratory tests for allelopathy have been criticized because the chemicals that act in the laboratory may not be effective in the field. Could this criticism be blunted by doing field experiments? Do you think that plants might evolve to produce chemical exudates that are not effective in the field?
Problem 11
Grizzly bears and black bears eat the same foods and live in similar places in North America. Grizzly or brown bears are much larger than black bears and more aggressive. All large islands off the coast of British Columbia and Alaska have either black bears or grizaly bears but no island has both species (Apps et al. 2006 ). Is this evidence for competition between these two bear species? What other evidence would you look for to show that grizzlies affect the local distribution of black bears?
