Patterns of Meiofauna Distribution

In a world of global environmental deterioration with an ever-increasing number of endangered species, the study of species distribution and dispersal has grown in importance and scientific attention among meiobenthologists. The potential to recolonize impoverished habitats and the risk of invasions by “neozoa” are fields of increasing awareness. This supports assessments, also on the level of meiofauna, of species distribution and richness, particularly in less studied biotopes, for instance in polar, tropical and deep-sea regions. Considerations relevant to this issue involve the distributional pathways that underlie the present patterns of distribution and the genetic diversification of populations. These general aspects will serve as a basic orientation before the meiofauna from selected biotopes is characterized (Chap. 8).

Meiofauna occur in all aquatic biotopes and climatic zones, from polar ice to alpine lakes, from hadal troughs to mangrove swamps. Of course, distribution patterns due to historical and/or biological characteristics underlie this ubiquitous occurrence. One of these patterns is the vicariant amphi-oceanic distribution of coastal species, well explored from the North American and European Atlantic coastlines (Ax and Armonies 1987; Stock 1994). The mechanisms of dispersal underlying these distributional patterns are not conclusive and are still remain debated. Potential pathways will be addressed, as will the opposite effects—mechanisms of restriction to isolated localities with a high rate of endemism. Especially for meiofauna, restricted distribution patterns are problematic for two reasons: (1) these patterns are often not based on comprehensive studies and only reflect local findings, while investigations from many potentially connecting areas are incomplete, and (2) the taxonomic affiliation often does not stand up to detailed examination with modern methods by experienced specialists.