Freshwater microcrustaceans (Copepoda: Cyclopidae) on islands: a review

Little is known about the insular diversity and its determinants in the freshwater invertebrates in comparison to land animals. Our goal is to obtain global-scale information on the insular diversity in Cyclopidae, test its relationships with the geographical variables in different types of islands, and compare the patterns to those observed in other organisms. In total 291 species and subspecies were reported in the 35 islands included in our analyses. The total and endemic species richness have strong positive correlations with surface area and maximum elevation of the islands; regression slopes are larger in the oceanic than in continental islands. Small-island effects occur in the relationships between the endemic species richness and area and elevation. Distance from mainland has negative correlations with the total and endemic species richness in the oceanic islands. Compositional similarity (in contrast to species richness) is determined by the geographic variables to only a minor extent, while space has stronger impact. The relationships found in Cyclopidae generally fit those observed in other predominantly terrestrial organisms, yet some characteristics (negative intercepts in the area-species and elevation-species relationships; large area and high elevation thresholds below which no endemic species occurs) are suggested to be specific to fresh waters.