Taxonomy, biogeography and DNA barcodes of G eodia species ( P orifera, D emospongiae, T etractinellida) in the A tlantic boreo‐arctic region

G eodia species north of 60° N in the A tlantic appeared in the literature for the first time when B owerbank described G eodia barretti and G . macandrewii in 1858 from western N orway. Since then, a number of species have been based on material from various parts of the region: G . simplex , I sops phlegraei , I . pallida , I . sphaeroides , S ynops pyriformis , G . parva , G . normani , G . atlantica , S idonops mesotriaena (now called G . hentscheli ), and G . simplicissima . In addition to these 12 nominal species, four species described from elsewhere are claimed to have been identified in material from the northeast A tlantic, namely G . nodastrella and G . cydonium (and its synonyms C ydonium muelleri and G eodia gigas ). In this paper, we revise the boreo‐arctic Geodia species using morphological, molecular, and biogeographical data. We notably compare northwest and northeast Atlantic specimens. Biological data (reproduction, biochemistry, microbiology, epibionts) for each species are also reviewed. Our results show that there are six valid species of boreo‐arctic A tlantic G eodia while other names are synonyms or mis‐identifications. G eodia barretti , G . atlantica , G. macandrewii , and G . hentscheli are well established and widely distributed. The same goes for G eodia phlegraei , but this species shows a striking geographical and bathymetric variation, which led us to recognize two species, G . phlegraei and G . parva (here resurrected). Some G eodia are arctic species ( G . hentscheli , G . parva ), while others are typically boreal ( G . atlantica , G . barretti , G . phlegraei , G . macandrewii ). No morphological differences were found between specimens from the northeast and northwest A tlantic, except for G . parva . The Folmer cytochrome oxidase subunit I ( COI) fragment is unique for every species and invariable over their whole distribution range, except for G. barretti which had two haplotypes. 18S is unique for four species but cannot discriminate G . phlegraei and G . parva . Two keys to the boreo‐arctic G eodia are included, one based on external morphology, the other based on spicule morphology. © 2013 The Linnean Society of London