Phylogenetic relationships within the Phyllidiidae (Opisthobranchia, Nudibranchia)

Abstract

The Phyllidiidae (Gastropoda, Heterobranchia, Nudibranchia) is a family of colourful nudibranchs found on Indo-Pacific coral reefs. Despite the abundant and widespread occurrence of many species, their phylogenetic relationships are not well known. The present study is the first contribution to fill the gap in our knowledge on their phylogeny by combining morphological and molecular data. For that purpose 99 specimens belonging to 16 species were collected at two localities in Indonesia. They were photographed and used to make a phylogeny reconstruction based on newly obtained (COI)cytochrome oxidase subunit sequences as well as sequence data from GenBank. All mitochondrial 16S sequence data available from GenBank were used in a separate phylogeny reconstruction to obtain information for species we did not collect. COI data allowed the distinction of the genera and species, whereas the 16S data gave a mixed result with respect to the genera Phyllidia and Phyllidiella. Specimens which could be ascribed to species level based on their external morphology and colour patterns showed low variation in COI sequences, but there were two exceptions: three specimens identified as Phyllidia cf. babai represent two to three different species, while Phyllidiella pustulosa showed highly supported subclades. The barcoding marker COI also confirms that the species boundaries in morphologically highly variable species such as Phyllidia elegans, Phyllidia varicosa, and Phyllidiopsis krempfi, are correct as presently understood. In the COI as well as the 16S cladogram Phyllidiopsis cardinalis was located separately from all other Phyllidiidae, whereas Phyllidiopsis fissuratus was positioned alone from the Phyllidiella species by COI data only. Future studies on phyllidiid systematics should continue to combine morphological information with DNA sequences to obtain a clearer insight in their phylogeny.

First Study on Marine Heterobranchia (Gastropoda, Mollusca) in Bangka Archipelago, North Sulawesi, Indonesia

“…Distribution of specific taxa is highly variable when comparing the different localities in BA (Table 2), with Chromodoris annae (46 individuals) and Phyllidiella pustulosa (39 individuals) dominating the overall collection and being encountered in almost all sites. Unpublished results confirm earlier results from Stoffel et al [25] and clearly show cryptic speciation in Phyllidiella pustulosa, with sympatric occurrences of the various clades in Bangka Archipelago, BNP, and the island of Sangihe. If these clades are considered separate species, the diversity would increase by five to seven species and thus render P. pustulosa a much less common species.…”

“…Each collected specimen was documented with an Olympus TG5 under water (when possible) and additionally in the laboratory, provided with a unique identifier (abbreviation of name, year, location, and number of specimen), and preliminarily identified with the help of available literature (e.g., [3][4][5]11,15,16,[20][21][22][23][24][25][26][27]). Gosliner et al [24] depict many undescribed species.…”

“…Phyllidiella pustulosa ( Figure 17E,F) is the most common species of the genus Phyllidiella and also within Phyllidiidae. However, this species was shown to represent a complex of several species [25], which are very difficult to distinguish by external characteristics alone. Figure 17G,H depict a specimen which we removed from the substrate to show feeding marks on the sponge.…”

Astonishing diversity revealed: an annotated and illustrated inventory of Nudipleura (Gastropoda: Heterobranchia) from Mozambique

“…As a result, there are currently eight synonyms for this species (Rosenberg & Bouchet 2012). However, recent molecular studies showed that P. pustulosa is likely to be a species complex with up to four molecular operational taxonomic units (Stoffels et al 2016). Therefore, this putative species complex and its geographic distribution needs further investigation.…”

“…The main distinction is associated with the outer longitudinal black bands: in the collected specimen, these bands are shorter and connect with the radial lines to create an inverted "V". As Phyllidia can be highly variable (Stoffels et al 2016), it is not possible to confirm the taxonomic status without further molecular or anatomical review.…”