Comparative Systematics of Subterranean Amphipod Crustaceans in the Families Crangonyctidae and Bogidiellidae

The research project presented in this doctoral dissertation deals with the systematics of two different taxonomic groups of subterranean amphipods (Crustacea). Therefore, rather than being a single project, this study is divided into several sub-projects. Altogether, the chapters for the sub-projects are composed of five publications. An introductory chapter and a summarizing discussion are added to provide a structural unit for the collection of papers and to compare the results of the individual projects. The thesis investigates the systematics of the amphipod families Bogidiellidae Hertzog, 1936, and Crangonyctidae Bousfield, 1973. Based on descriptive taxonomy according to modern standards, revisions are given for the crangonyctid genus Bactrurus Hay, 1902, the bogidiellid genus Spelaeogammarus da Silva Brum, 1973, and the family Bogidiellidae. The bogidiellid sub-project also includes the description of the new genus and species Megagidiella azul. This study makes an attempt to compile and evaluate molecular and morphological data for two families of gammaridean amphipods. To research the phylogenetic relationships of the Bogidiellidae and Crangonyctidae, cladistic analyses, using external morphological characters, are conducted for each family. In addition, sequence analyses of the 18S (small subunit) rDNA gene are carried out for three species of Bactrurus and several selected amphipod taxa. The results of morphological and molecular analyses are compared and the phylogenetic relationships of the taxa under investigation are discussed, especially emphasizing their biogeographic distribution patterns and current taxonomic classification. In a summarizing chapter, the biogeography and evolutionary history of both families are compared. Moreover, the application of different methods of phylogenetic reconstructions is discussed for the Bogidiellidae and Crangonyctidae, as well as for stygobiont amphipods in general