To be or not to be? What molecules say about <em>Runcina brenkoae</em> Thompson, 1980 (Gastropoda: Heterobranchia: Runcinida)

Abstract

Runcinids are poorly known minute marine slugs inhabiting intertidal and shallow subtidal rocky shores. Among the European species, Runcina brenkoae, described from the Adriatic Sea in the Mediterranean, has been described to display chromatic variability, placing in question the true identity and geographic distribution of the species. In this paper we investigate the taxonomic status of R. brenkoae based on specimens from the central and western Mediterranean Sea and the southern Iberian coastline of Portugal and Spain, following an integrative approach combining multi-locus molecular phylogenetics based on the mitochondrial markers cytochrome c oxidase subunit I and 16S rRNA and the nuclear gene histone H3, together with the study of morpho-anatomical characters investigated by scanning electron microscopy. To aid in species delimitation, the Automatic Barcode Gap Discovery and Bayesian Poisson tree process methods were employed. Our results indicate the existence of a complex of three species previously identified as R. brenkoae, namely two new species here described (R. marcosi n. sp. and R. lusitanica n. sp.) and R. brenkoae proper.

New mitogenomes of Runcinidae and Facelinidae: two understudied heterobranch families (Mollusca: Gastropoda)

“…Members of this order feed on algae and dead marine phanerogams, contributing to the decomposition of organic matter and, therefore, being an invaluable element in carbon and nitrogen cycling in oceans (Araujo et al. 2019 ). Due to their small size and difficulties in finding them in their natural environment, very few studies have focused on them so far.…”

Runcinidae and Facelinidae: Two complete mitogenomes of understudied and misleading heterobranch families (Gastropoda, Mollusca)

“…1), genus belonging to the order Runcinidae, which englobe close to 100 small sized species (1-4mm) described so far, although it is thought to include much more biodiversity (Araujo et al, 2022). The members of such order feed on macroalgae, contributing to the decomposition of dead matter, being a key element in the balance of the ecosystem (Araujo et al, 2019). However, due to the small size and difficulty to find them in their natural environment, few studies have focused on them so far.…”

Two Seas for One Great Diversity: Checklist of the Marine Heterobranchia (Mollusca; Gastropoda) from the Salento Peninsula (South-East Italy)

“…Recently, Onorato and Belmonte [38] reviewed the biodiversity assessment of the marine submerged caves in the Salento peninsula, which includes some heterobranchs, while Micaroni et al [39] published a check-list of Heterobranchia from the Ionian locality of Tricase, adding 20 species to Perrone's previous lists [30][31][32][33][34][35][36][37]. Finally, several published papers that did not have proper checklists, added new records of single species sampled from the Salento Peninsula [29,[40][41][42][43][44], contributing to the increase of lists of species known from this Apulian area. However, to date, there is no published checklist of marine Heterobranchia fauna from the Adriatic side of the Salento peninsula.…”