Grania CF. LEVIS COATES & ERSEUS 1985

GRANIA CF. LEVIS COATES & ERSÉUS, 1985

Material examined

USNM 1283176, CE11570, whole-mounted, sexually immature specimen, with some segments amputated, from off North Carolina, USA, 33°10′23″N, 76°45′23″W. Continental shelf slope, 492 m in depth, sand. Collected by C. Erséus, 20 May 2011. COI barcode KT428114; for other genes, see Table 1.

Remarks

This barcoded, but immature specimen, and thus unsuitable for complete morphological description, was included in the phylogenetic analysis, to enlarge the taxonomic sampling from the north-western Atlantic region. Phylogenetically, this specimen came out as closely related to G. carolinensis sp. nov. (Fig. 15), but it is morphologically distinct by its complete lack of chaetae. The latter trait suggests that this specimen could belong to Grania levis Coates & Erséus, 1985, originally described from somewhat further north, from Georges Bank, south-east of Massachusetts, USA.

GENETIC ANALYSES

COI clustering

The Bayesian inference of the COI sequences divide the 38 individuals into ten well-supported clades (Fig. 11), four of which are found in South Africa, two in Chile, one in Brazil, and three in the North Atlantic. Within-clade variation is generally low, but in one clade, i.e. all specimens referred to the new taxon G. chilensis sp. nov., there is a notable subclustering pattern, dividing this clade into four subclades. A haplotype network (Fig. 12) indicates that G. chilensis sp. nov. is structured geographically, with two subclades found in the southernmost site (Valdivia), one subclade in the northernmost site (Coquimbo), and an intermediate subclade in the intermediately located site (Concepcion). Pairwise genetic distances indicate that in general there is a strong barcoding gap present between lineages within this group. In the G. chilensis sp. nov. clade, however, there is higher than average within-species divergence, although not nearly as great as the lowest between-species differences (Fig. 13).

ITS clustering

The Bayesian inference analysis of 23 ITS sequences supports all ten clusters found in the mitochondrial data (Fig. 14); however, although there is also variation within the G. chilensis sp. nov. cluster in the ITS region, the geographic substructuring is not seen here. Instead, the variation seems to be randomly distributed with respect to geography.

Phylogenetic placement of new species

The updated phylogeny is completely congruent with that described in De Wit et al. (2011b), containing three main clades (A, B, C in Fig. 15). All of the South African species form one strongly supported clade within clade A, together with all the North Atlantic species. By contrast, the Chilean and the Brazilian species are placed in clade B, together with Grania curta De Wit & Erséus, 2007 and G. americana. Grania unitheca sp. nov. from shallow water in North Carolina (North Atlantic) is placed together with the other North American species G. monospermatheca (its sister taxon) and G. laxartus; however, G. carolinensis sp. nov. and the closely related immature specimen of Grania cf. levis, both found in deep water off the North Carolinian coast, are placed as the sister clade of G. postclitellochaeta and the cryptic G. occulta, whereas G. ovitheca, which is morphologically identical to G. occulta, is strongly supported as the sister to this four-taxon group (Fig. 15).