Richness of littoral macroinvertebrate communities in mountain ponds from NW Spain: what factors does it depend on?

Recent researches have started to provide useful information on the littoral macroinvertebrates living in European mountain ponds. However there is still uncertainty on the factors really shaping their communities. Understanding patterns of biodiversity in these systems is essential for conservation and management purposes. In this paper we sampled littoral macroinvertebrates at 51 mountain ponds from a wide Spanish region (Castilla y Leon) in order to define which of a set of environmental variables were responsible for differences in richness (genus level or above). One macroinvertebrate sample was collected at each pond (in late June or early July between 2004 and 2008) by kicking and sweeping following a multihabitat time-limited sampling. Twenty-four variables measured at 39 ponds were used to generate a predictive model by multiple linear regression. This model revealed number of habitats and fish stocking as the only significant variables, showing their relative importance against variables traditionally considered to influence richness in mountain ponds and lakes (for example, altitude and pond size). Furthermore, this model accurately predicted richness when tested on a new set of twelve ponds. Additional data analyses proved that neither altitude nor habitat type significantly influenced macroinvertebrate richness, while water permanence had a slight effect (the number of taxa was slightly lower in temporary than in permanent ponds).