Cryptic diversity of Melanochlamys sea slugs (Gastropoda, Aglajidae) in the North Pacific

Abstract

North Pacific specimens of Melanochlamys sea slugs were examined morphologically (including the male reproductive morphology, shell and external coloration) and were sequenced for three genes (mitochondrial COI and 16S and nuclear H3). Phylogenetic and species delimitation analyses were used to determine the evolutionary relationships and species diversity among the specimens examined. Both molecular and morphological data revealed an unexpected high level of cryptic diversity. At least four distinct species occur on the Northwestern Pacific. Melanochlamys ezoensis occurs in Russia and temperate and cold areas in Japan. Three additional undescribed species occur in Japan and/or South Korea. One of the undescribed species occurs both in South Korea and in Japan, but only in Tokyo Bay, suggesting that it could be non‐native in Japan. Two distinct species occur on the Northeastern Pacific coast; Melanochlamys diomedea is widespread from Southern California to Alaska, whereas M. ezoensis was found only in San Francisco Bay, suggesting a human‐mediated introduction. This is further supported by the absence of records of M. ezoensis in San Francisco prior to 2001. The species diversity of Melanochlamys in the Northwestern Pacific is much greater than in the Northeastern Pacific; it is hypothesized that differences in geographic and ocean current system complexity might account for different responses to glacial extinction and postglacial expansion.

Molecular evidences confirm the taxonomic separation of two sympatric congeneric species (Mollusca, Gastropoda, Neritidae, Neritina)

“…These results are compatible with the values found to delimit species in different groups of gastropods (e.g. Churchill et al 2014;Cooke et al 2014;Espinoza et al 2014). Numbers on and below the main branches represent the posterior Bayesian probabilities (BP) (>0.90) and bootstrap values for maximum likelihood (ML) (>70%), respectively.…”

Aeolidia papillosa(Linnaeus, 1761) (Mollusca: Heterobranchia: Nudibranchia), single species or a cryptic species complex? A morphological and molecular study

“…Developments in molecular biology, population genetics, and phylogeographic methods have boosted research on diversity and evolution in the marine environment. Molecular methods have highlighted the presence of several cryptic species in Heterobranchia (Carmona et al ., ,b; Cooke et al ., ; Espinoza, DuPont & Valdés, ; Padula et al ., ; Pola, Roldán & Padilla, ; Shipman & Gosliner, ; Wilson & Burghardt, ). Therefore, the wide and discontinuous geographic range of A. papillosa , as well as its variability in coloration, suggests that we may be dealing with more than a single species.…”

Molecular phylogeny of Glossodoris (Ehrenberg, 1831) nudibranchs and related genera reveals cryptic and pseudocryptic species complexes

“…However, historically their systematics have been poorly understood with many species either misclassified and unidentified, or simply glossed over (pun intentional) (Rudman, 1985(Rudman, , 1986. Species that rely heavily on colour pattern for defence through crypsis, camouflage or mimicry can be morphologically difficult to distinguish both in the field and taxonomically (Amato et al, 2007;Pinhal et al, 2012;Cooke et al, 2014). Many nudibranchs exhibit aposematic coloration or exquisite mimicry or camouflage (Rudman, 1991;Gosliner, 2001;Moore and Gosliner, 2009), and it is therefore no surprise that with the addition of molecular sequencing and the resulting data, there has been a substantial increase in the identification of species complexes within previously defined species across Nudibranchia (Wilson et al, 2009;Gosliner and Fahey, 2011;Pola et al, 2012Pola et al, , 2014Lindsay and Vald es, 2016).…”