A look back in time - Toward an historical biogeography as a synthesis of systematic and geologic patterns outlined with limnic gastropods

The present distributions of living organisms over the world's surface are the result of past events such as vicariance and dispersal. Historical biog eographers aim to record the distribution of organisms in space and time, t o reconstruct the history of taxa and areas and thus to reconcile biologica l patterns with those of geology. In discerning distributional patterns of different taxa and in trying to understand how these patterns are related t o the geology of the region, the vicariance approach to historical biogeogr aphy has witnessed a growing interest over the last three decades. New meth odologies in systematics resulting from phylogenetic and cladistic approach es, and new geological evidence developing from the emergence of plate tect onic theory have modernized and revolutionized biogeography since the 1960s . This is characterized by attempts to formalize standard procedures sugges ted by panbiogeography and cladistic biogeography. A diverse array of proto cols have been developed to evaluate the distribution of organisms, among t hem the translation of taxon cladograms into area cladograms and their comp arison for congruence. Unfortunately, most systematists continue to conside r biogeography as either a mere appendix to taxonomic treatments (descripti ve biogeography) or as unjustified "story telling". This paper reviews the history, implications and differences of the various approaches (ecological vs. historical biogeography, dispersalism vs. vicariance biogeography, pan biogeography vs. phylogenetic and cladistic biogeography), and presents a b rief overview of ongoing studies and their implications utilizing limnic sn ails of the caenogastropod superfamily Cerithioidea. Its purpose is to outl ine avenues for future biogeographical research proposed by various researc hers that will ultimately lead to a synthesis of systematic and geological patterns. Discussing current issues of biogeographical theory, the argument is made for renewed consideration of dispersal as a valid component of bio geographic explanations in addition to the now common assumption of vicaria nt events and against oversimplified taxon/area analogy.