Phylogeny and vicariance biogeography of North Atlantic Chalinidae (Haplosclerida, Demospongiae)

The present paper consists of a phylogenetic and historical biogeographic analysis of the North Atlantic shallow-water Haplosclerida (Porifera, Demospongiae), and of the Chalinidae in particular. The monophyly of the Haplosclerida is founded on five assumed apomorphous (derived) characters. Six related outgroups, viz. the Esperiopsidae, Desmacellidae, Mycalidae, Myxillidae, Microcionidae, and Axinellida s.l. have been used for establishing the character polarity within the Haplosclerida. A key to the haplosclerid families, the Chalinidae, Niphatidae, Callyspongiidae, Petrosiidae and Oceanapiidae, and a hypothesis on the phylogenetic relationships of the families is presented. Within the Chalinidae, eight monophyletic species groups are distinguished on the basis of assumed apomorphous characters. Two of these groups belong to the nominal genera Acervochalina and Dendroxea, the other six to the genus Haliclona. A key to the species groups and a hypothesis on the phylogenetic relationships of the groups is presented. Subsequently, each individual species group is analyzed phylogenetically. The obtained species cladograms and the distributional types of the species within the North Atlantic Ocean are used for the construction of a general area cladogram, representing a hypothesis on the historical relationships of areas of endemism in the North Atlantic Ocean. The analysis is based on the component-compatibility and parsimony methods as developed by Zandee & Roos (1987). For generation of the general area cladogram the computer program CAFCA (Zandee, 1987) has been used. Three main vicariance events can be recognized from the general area cladogram, viz. the Cretaceous separation of South America and Africa, a subsequent separation of the Boreal area from the south-eastern part of the North Atlantic and the Mediterranean, and the Miocene (Messinian) salinity crisis in the Mediterranean basin. The individual species area cladograms are evaluated in order to establish which show “vicariance fit” with the general area cladogram, and which species have deviating distribution patterns needing the most parsimonious “ad hoc” explanations, like dispersal or extinction.