Habitat constraints and the generation of diversity in freshwater macroinvertebrates.

Abstract

Abstract Freshwater aquatic invertebrates occupy a range of habitats, which can broadly be classified into running or standing waters. The contrasting habitat permanence over geological timescales of these two habitat types imposes different constraints on their invertebrate populations. Species in more ephemeral lentic water bodies are forced to disperse when the habitat disappears, and are thus predicted to have higher dispersal abilities and interpopulation gene flow, resulting in larger, more dynamic geographical ranges and slower evolutionary turnover. In the more stable lotic habitats, species are predicted to have lower dispersal abilities, with higher persistence of local populations and reduced interpopulation gene flow. This should result in smaller range sizes and a higher evolutionary turnover. Latitudinal diversity gradients of lentic and lotic species may also be expected to differ, as lotic species will be more dependent on historical factors and distance to glacial refugia, whereas lentic species will be closer to an equilibrium with current ecological and geographical conditions. Some of these predicted patterns have been demonstrated for a range of aquatic invertebrates across different geographical areas, although the underlying evolutionary and physiological mechanisms are still poorly understood.