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A PHYLOGEOGRAPHIC STUDY OF THE GENUS PENTAPORA (BRYOZOA ; CHEILOSTOMATA) IN NORTH WEST EUROPE AND THE MEDITERRANEAN

Pentaporidae is a well recognised family of ascophoran cheilostome bryozoans which includes the genus Pentapora. Honeycombed, domed colonies, with dicotomic or laminar branches and a diameter of 20–30 cm or up to 1 m are often formed. They grow on organisms as epibionts or develop micro-reefs on the rocky seabed. Detailed morphological studies have refined the taxonomy of Pentaporidae and the geographic distribution is described from the North Atlantic to the Mediterranean. Gautier (1962) considered P. fascialis and P. foliacea to be different species, later the two species were given the status of subspecies (Zabala and Maluquer, 1988 ; Alvarez, 1991). In recent years, the two forms have been finally classified as a single species P. fascialis (Hayward and Ryland, 1999 ; Chimenz-Gusso et al., 2005). Our purpose is to establish the phylogeography of Pentapora fascialis using molecular methods, combined this with morphological analysis of recent specimens collected from different regions of Europe, in order to clarify species status. Collection and mapping of Pentapora colonies from UK and Mediterranean populations were conducted between July 2006 and September 2008. Morphological features and skeletal structures were analyzed using a Hitachi FESEM microscope. DNA was extracted from fresh samples and sequence analysis of mitochondrial and nuclear genes was conducted. Comparison of Atlantic samples versus Mediterranean ones and colonies with dichotomic branches versus colonies with laminar branches, revealed no differences in terms of morphology and main zooid structures. High magnification pictures revealed diversity in skeletal ultrastructures (i.e. appearance of mineralogical crystals which compose frontal wall layers) by comparing Atlantic and Mediterranean samples. The differences may be related to variation in the mineralogical composition of frontal wall related to seawater temperature condition experienced by the colonies during their growth. Bayesian analysis reveals genetic differentiation between Atlantic and Mediterranean basins, with the Atlantic populations occurring as a monophyletic sister group arising from the Mediterranean populations. Hypotheses for these patterns are discussed along with the taxonomic implications of these findings.

Bryozoa; Pentapora

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