Abstract
Understanding the mechanisms that maintain diversity is important for managing ecosystems for species persistence. Here we used a long-term data set to understand mechanisms of coexistence at the local and regional scales in the Cape Floristic Region, a global hotspot of plant diversity. We used a dataset comprising 81 monitoring sites, sampled in 1966 and again in 1996, and containing 422 species for which growth form, regeneration mode, dispersal distance and abundances at both the local (site) and meta-community scales are known. We found that species presence and abundance were stable at the meta-community scale over the 30 year period but highly unstable at the local scale, and were not influenced by species' biological attributes. Moreover, rare species were no more likely to go extinct at the local scale than common species, and that alpha diversity in local communities was strongly influenced by habitat. We conclude that stochastic environmental fluctuations associated with recurrent fire buffer populations from extinction, thereby ensuring stable coexistence at the meta-community scale by creating a “neutral-like” pattern maintained by niche-differentiation.
Highlights
Ecologists have always been intrigued by how species coexist [1], especially in species-rich communities [2]
Heuristic and parsimonious models that assume biological neutrality [4] may not be a true reflection of reality and can be misleading or meaningless to ecological managers who require guidelines that are underpinned by theories and models that are useful in practice [5]
Theoretical and empirical research has demonstrated the key role of environmental variability in maintaining species richness in plant communities [6,7,8,9]
Summary
Ecologists have always been intrigued by how species coexist [1], especially in species-rich communities [2]. A potent form of environmental variation is associated with variation in fire regime components (frequency, season and intensity), which significantly influences the composition and diversity of plant communities at the local scale [11]. This is especially true of the Mediterranean shrublands of South Africa (fynbos) and Australia (kwongan) [12] that support landscapes which, after the wet tropics, are the most species-rich in the world [13]
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