: The SLOSS debate can only be resolved by considering the optimal spatial configuration of a nature-reserve system. Only when target species have been identified by such considerations can the size of the constituent reserves be determined. We explored two null models for a spatial configuration of reserves in the Cape Floristic Region, South Africa, based on the distribution of species in the family Proteaceae (Angiospermae: Rosidae). In the first model, reserves (12 × 13 km grid squares) were assigned at random for comparison with existing, proposed, and theoretically ideal configurations. In the second model, the theoretically ideal reserve configuration was constructed using the first model as a preassigned configuration. Two methods were used to iteratively select a reserve from the grid system: richness of unprotected species (species-richness algorithm), and the sum of the rarity indexes for each unprotected species (rarity algorithm). Both algorithms yielded configurations requiring fewer reserves than those contained in proposed or existing configurations, although neither algorithm was perfect. The existing reserve configuration performed no better than the random model, assuming that the principal goal is protection of all species. We confirm that the best approach to designing a reserve configuration that maximizes the protection of species richness is to identify areas of high endemism and richness within particular biogeographical regions.
Resumen: El debate “SLOSS” solo podra ser resuelto si se considera la configuracion espacial optima de un sistema de reservas naturales. El tamano de las reservas que constituiran el sistema no podra ser determinado sin antes haber identificado a las especies apropiadas basandose en las consideraciones antes mencionadas. Exploramos dos modelos nulos para la configuracion espacial de las reservas en la Region Floristica del Cabo, Sudafrica, en base a la distribucion de las especies de la familia de las Proteaceas (Angiospermae: Rosidae). En el primer modelo, las reservas (rectangulos de 12 × 13 km de lado) fueron asignadas al azar a los efectos realizar comparaciones con las configuraciones que existen actualmente, aquellas que han sido propuestas y finalmente con aquellas que son teoricamente ideales. En el segundo modelo, la configuracion teoricamente ideal fue construida usando el primer modelo como la configuracion preasignada. Se utilizaron dos metodos para seleccionar iterativamente una reserva del total existente en el sistema de cuadriculado: la riqueza de especies no protegidas (algoritmo riqueza de especies); y la suma del los indices de rareza para cada especie no protegida (algoritmo de rareza). Si bien ningun algoritmo fue perfecto, ambos dieron como resultado configuraciones que requieren un menor numero de reservas que las requeridas por configuraciones ya propuestas o existentes en la actualidad. Suponiendo que el objetivo principal es la proteccion de todas las especies, los resultados obtenidos usando la configuracion de las reservas existentes en la actualidad no fueron mejores que aquellos obtenidos usando el modelo aleatorio. Confirmamos que la mejor estrategia para disenar la configuracion de reservas que maximice la riqueza de especies es identificar areas con also endemismo y riqueza dentro de regiones biogeograficas particulares.
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