Molecular Phylogenetic Evaluation of Classification and Scenarios of Character Evolution in Calcareous Sponges (Porifera, Class Calcarea)

Calcareous sponges (Phylum Porifera, Class Calcarea) are known to be taxonomically difficult. Previous molecular studies have revealed many discrepancies between classically recognized taxa and the observed relationships at the order, family and genus levels; these inconsistencies question underlying hypotheses regarding the evolution of certain morphological characters. Therefore, we extended the available taxa and character set by sequencing the complete small subunit (SSU) rDNA and the almost complete large subunit (LSU) rDNA of additional key species and complemented this dataset by substantially increasing the length of available LSU sequences. Phylogenetic analyses provided new hypotheses about the relationships of Calcarea and about the evolution of certain morphological characters. We tested our phylogeny against competing phylogenetic hypotheses presented by previous classification systems. Our data reject the current order-level classification by again finding non-monophyletic Leucosolenida, Clathrinida and Murrayonida. In the subclass Calcinea, we recovered a clade that includes all species with a cortex, which is largely consistent with the previously proposed order Leucettida. Other orders that had been rejected in the current system were not found, but could not be rejected in our tests either. We found several additional families and genera polyphyletic: the families Leucascidae and Leucaltidae and the genus Leucetta in Calcinea, and in Calcaronea the family Amphoriscidae and the genus Ute. Our phylogeny also provided support for the vaguely suspected close relationship of several members of Grantiidae with giantortical diactines to members of Heteropiidae. Similarly, our analyses revealed several unexpected affinities, such as a sister group relationship between Leucettusa (Leucaltidae) and Leucettidae and between Leucascandra (Jenkinidae) and Sycon carteri (Sycettidae). According to our results, the taxonomy of Calcarea is in desperate need of a thorough revision, which cannot be achieved by considering morphology alone or relying on a taxon sampling based on the current classification below the subclass level

Fiber SMF-28 Datasheet

<p>The hypothesis (constrained monophyly) can be rejected for p-values <0.05.</p

Organization of choanoskeleton.

<p>A: inarticulated (<i>Sycettusa</i> aff. <i>hastifera</i>); B: articulated (<i>Grantessa</i> sp. GW974).</p

Different organizations of the aquiferous system in Calcarea.

<p>A: asconoid (<i>Soleneiscus radovani</i>); B: syconoid (<i>Sycon coronatum</i>, from Helgoland, Germany); C: sylleibid (<i>Grantiopsis cylindrica</i>); D: leuconoid (<i>Leucettusa</i> sp. 1). Thin arrows illustrate the direction of water flow in A, B and C. atr = atrium; chc = choanocyte chambers; cx = cortex; eh = exhalant channel; ext: exterior of the sponge; ih = inhalant channel; spt = spicule tract of modified triactines.</p

Included specimens of Calcaronea, their sample localities and GenBank accession numbers.

<p>New specimens and sequences are in bold.</p>*<p> = Specimen is the holotype;</p>#<p> = SSU sequence comes from another individual (GenBank).</p

Skeletal organization of Grantiidae of clade LEUC I.

<p>A,B: <i>Ute</i> aff. <i>syconoides</i> (GW975) in cross section (A) and longitudinal section (B); C: Cross section of <i>Synute pulchella</i>; D: Cross section of <i>Aphroceras</i> sp. Arrows point to the giant longitudinal diactines. atr = atrium; ch = choanosome; cx = cortex, ext = exterior of the sponge.</p