Questions: 1) What could account for the reversal against expectation?
Answer: size of the mainland pool of species, lack of differences in dispersal ability among the mainland species, and competition between species. 2) Why aren’t all species equal in the larger context?
Answer: Some species live in much greater jeopardy of extinction than others. The rare species, the highly specialized species, the less competitive species, and the species having low aptitude for dispersal and colonization, all these species might be missing from a reserve system if the reserves were numerous but small. 3) Why should the number of extinctions be inversely related to reverse size?
Answer: reserve size will determine population size for each species and small populations face special jeopardizes. 4) How should the equilibrium number of species on a large reserve? Answer: It should be greater than the equilibrium number on a small reserve, but it doesn’t distinguish between a large reserve full of common species and a large reserve full of rare species. 5) Why did Diamond think that the theory of Simberloff has some mistakes? Answer: Simberloff’s reasoning from their assumptions is correct but minimizes or ignores much more important conservation problems. Because those indifferent to biological conservation may seize on Simberloff’s report as scientific evidence that large refuges are not needed, it is important to understand the flaws in their reasoning. 6) Why does a large reserve receive more immigration and endure less extinction? Answer: A large reserve presents a bigger target to dispersing individuals, hence a higher immigration rate. A large reserve supports large populations, thereby buffering each species against the dangers of rarity, hence a lower extinction rate. A higher immigration rate combined with a lower extinction rate results in a larger number of species at equilibrium.
Important points: 1) The theory of Simberloff and Abele has some problems: two small islands sometimes contain more species than a large one. It might be true in certain circumstance, but it was irrelevant. Because the sheer number of species present on some island or group of islands, or within some wildlife reserve or group of reserves, was not the real issue. The real issue was how an island or a reserve might affect extinction or preservation of particular species in the larger context. 2) The idea of Diamond is an important point for the theory: A refuge system that contained many species like starling and house rat while losing only a few species like ivory – billed woodpecker and timber wolf would be a disaster. 3) A single large reserve would offer greater security within its interior, while several small reserves would suffer proportionately more disturbance along their edges. It might provide a margin of safety against climate change. If one region of the reserve became too dry or too hot for a given species, that species might be able to move to a wetter or cooler region without being stopped by a boundary. A small reserve would afford no such migrational latitude. It might be more cost effective for saving tropical insects and rare plants, which tend to be localized within small pockets of habitat. 4) Several predictions follow from the hypothesis that nature reserves are analogous to land bridge islands. There are: total number of extinctions should exceed total number of colorizations within a reserve, number of extinctions should be inversely related to reserve size, and number of extinctions should be directly related to reverse age. 5) The area effect, the distance effect, habitat diversity, edge effects, small scale changes in climate, relationships between species, and the vagaries of change are all implicated in the biological dynamics of forest fragments.