Lillehammer University College, PO Box 952, N-2604 Lillehammer, Norway.
J Theor Biol. 2010 May 21;264(2):604-12. doi: 10.1016/j.jtbi.2010.02.009. Epub 2010 Feb 10.
The SLOSS debate--whether a single large reserve will conserve more species than several small--of the 1970s and 1980s never came to a resolution. The first rule of reserve design states that one large reserve will conserve the most species, a rule which has been heavily contested. Empirical data seem to undermine the reliance on general rules, indicating that the best strategy varies from case to case. Modeling has also been deployed in this debate. We may divide the modeling approaches to the SLOSS enigma into dynamic and static approaches. Dynamic approaches, covered by the fields of island equilibrium theory of island biogeography and metapopulation theory, look at immigration, emigration, and extinction. Static approaches, such as the one in this paper, illustrate how several factors affect the number of reserves that will save the most species. This article approaches the effect of different factors by the application of species-diversity models. These models combine species-area curves for two or more reserves, correcting for the species overlap between them. Such models generate several predictions on how different factors affect the optimal number of reserves. The main predictions are: Fewer and larger reserves are favored by increased species overlap between reserves, by faster growth in number of species with reserve area increase, by higher minimum-area requirements, by spatial aggregation and by uneven species abundances. The effect of increased distance between smaller reserves depends on the two counteracting factors: decreased species density caused by isolation (which enhances minimum-area effect) and decreased overlap between isolates. The first decreases the optimal number of reserves; the second increases the optimal number. The effect of total reserve-system area depends both on the shape of the species-area curve and on whether overlap between reserves changes with scale. The approach to modeling presented here has several implications for conservational strategies. It illustrates well how the SLOSS enigma can be reduced to a question of the shape of the species-area curve that is expected or generated from reserves of different sizes and a question of overlap between isolates (or reserves).
SLOSS 争论——一个大保护区是否比几个小保护区能保留更多的物种——发生在 20 世纪 70 年代和 80 年代，至今仍未得到解决。保护区设计的首要原则是，一个大保护区将保留最多的物种，这一规则受到了强烈质疑。经验数据似乎削弱了对一般规则的依赖，表明最佳策略因情况而异。建模也被应用于这场争论。我们可以将解决 SLOSS 之谜的建模方法分为动态和静态方法。动态方法涵盖岛屿生物地理学的岛屿平衡理论和复合种群理论领域，研究的是移民、灭绝和灭绝。静态方法，如本文所述，说明了几个因素如何影响保留最多物种的保护区数量。本文通过物种多样性模型的应用来探讨不同因素的影响。这些模型将两个或多个保护区的物种-面积曲线结合起来，对它们之间的物种重叠进行了修正。这些模型对不同因素如何影响最佳保护区数量产生了几种预测。主要预测有：保护区之间的物种重叠增加、保护区面积增加时物种数量增长加快、最小面积要求提高、空间聚集和物种丰度不均匀时，保护区的数量减少、面积增大。较小保护区之间距离增加的影响取决于两个相互抵消的因素：隔离导致的物种密度降低（增强了最小面积效应）和隔离体之间重叠的减少。前者降低了最佳保护区的数量；后者增加了最佳保护区的数量。整个保护区系统面积的影响取决于物种-面积曲线的形状以及保护区之间的重叠是否随尺度而变化。本文提出的建模方法对保护策略有几个启示。它很好地说明了如何将 SLOSS 之谜简化为对不同大小保护区的物种-面积曲线的形状以及隔离体（或保护区）之间重叠的问题。
