Relative contribution of small mountain ponds to regional richness of littoral macroinvertebrates and the implications for conservation

Abstract

ABSTRACT Biodiversity is a central concept in conservation programme design. Until recently, ponds were neglected habitats probably owing to their small size and to the ignorance of their real conservation value. The classical theory of species‐area relationship (SAR) might apparently support such a view by predicting low richness values in small habitat patches. SAR theory does not take into account the fact that groups of small habitat patches can significantly contribute to regional richness, regardless of their overall small area. This work intends to contribute to the SLOSS (single large or several small) debate with data on littoral macroinvertebrates from mountain ponds. Do groups of small ponds support communities with higher biodiversity than a single large lake? Littoral macroinvertebrate richness, both local and regional, were measured in 17 ponds and one large lake from Sanabria Natural Park (NW Spain). In order to guarantee valid comparisons among systems, observed and estimated richness, as well as rarefaction methods were used. Although local richness in the lake was much higher than in any single pond, regional richness of ponds widely exceeded the value measured in the lake regardless of their small overall area. Six to seven ponds were enough to obtain an accumulated average richness equivalent to that in the lake. This pattern may be caused partly by increased habitat heterogeneity as proposed by the niche theory. Metacommunity theory might help to explain the high regional richness measured in the group of ponds in the study area. Whatever the explanation, it is evident that groups of mountain ponds strongly contribute to regional richness, a conclusion that should be taken into account by management programmes. There is a gap in this respect in European legislation (the EC Habitats Directive and Water Framework Directive), which fails to include groups of ponds as an additional habitat category. Copyright © 2012 John Wiley & Sons, Ltd.