From Persian Gulf to Indonesia: interrelated phylogeographic distance and chemistry within the genus Peronia (Onchidiidae, Gastropoda, Mollusca)

Abstract

the knowledge of relationships between taxa is essential to understand and explain the chemical diversity of the respective groups. Here, twelve individuals of the panpulmonate slug Peronia persiae from two localities in persian Gulf, and one animal of P. verruculata from Bangka island, indonesia, were analyzed in a phylogenetic and chemotaxonomic framework. Based on the ABGD test and haplotype networking using coi gene sequences of Peronia specimens, nine well-supported clades were found. Haplotype network analysis highlighted a considerable distance between the specimens of P. persiae and other clades. Metabolomic analysis of both species using tandem mass spectrometrybased GnpS molecular networking revealed a large chemical diversity within Peronia of different clades and localities. While P. persiae from different localities showed a highly similar metabolome, only few identical chemical features were found across the clades. the main common metabolites in both Peronia species were assigned as polypropionate esters of onchitriols and ilikonapyrones, and osmoprotectant amino acid-betaine compounds. On the other hand, the isoflavonoids genistein and daidzein were exclusively detected in P. persiae, while cholesterol and conjugated chenodeoxycholic acids were only found in P. verruculata. flavonoids, bile acids, and amino acid-betaine compounds were not reported before from onchidiidae, some are even new for panpulmonates. our chemical analyses indicate a close chemotaxonomic relation between phylogeographically distant Peronia species. Peronia Fleming, 1822, a panpulmonate slug genus, is typically distributed in tropical and subtropical regions of the Indo-Pacific ocean 1. The genus Peronia, with ten acknowledged species, has been reported from many localities ranging from the Indo-Pacific to the East Coast of Africa and to Hawaii 2-4. Due to undetected cryptic speciation, species diversity is often underestimated while the widespread distributions attributed to species is often overestimated 5. The integration of molecular and morphological methods has led to numerous discoveries of cryptic species complexes 6. This is also true for the genus Peronia, as was shown by Maniei et al. 3. To date, only three Peronia species are well investigated by molecular and/or morphology data, i.e.

Systematic revision of the genus Peronia Fleming, 1822 (Gastropoda, Euthyneura, Pulmonata, Onchidiidae)

“…Using DNA sequences to create a new species name while most species are not being included in phylogenetic analyses is highly problematic. Maniei et al (2020b) used the same mitochondrial COI sequences as in Maniei et al (2020a) to compare metabolites between the Peronia slugs they called P. persiae and one Peronia individual from Bangka Island, near Sumatra, Indonesia. That specimen from Bangka Island, identified as Peronia sp.…”

“…That specimen from Bangka Island, identified as Peronia sp. 7 by Maniei et al (2020a) and as P. verruculata by Maniei et al (2020b), belongs to the unit #1 of P. verruculata: its COI (MK993397) and 16S (MK993396) sequences cluster within unit #1. Note that the GenBank accession numbers for COI and 16S are switched in Maniei et al's (2020a) Table 2.…”

“…Note that the GenBank accession numbers for COI and 16S are switched in Maniei et al's (2020a) Table 2. Maniei et al (2020b) summarized their rationale for creating the name P. persiae as follows: "The ABGD test revealed that specimens of P. persiae form a separate clade (clade 2). Thus, the specimens from two localities of the Persian Gulf (Iran), i.e.…”

“…Goulding et al 2018c;Dayrat et al 2019a). Maniei et al (2020b) argue that research on metabolites requires sound taxonomic knowledge. That certainly is a commendable goal: indeed, any comparative work in any biological field should be based on correct taxonomy.…”

“…Unfortunately, P. persiae is a junior synonym of both P. gondwanae and P. verruculata (Tables 1, 6). So, the metabolites compared between "P. persiae" and "P. verruculata" merely are intra-specific differences (within P. verruculata) due to the long geographic distance (between the Persian Gulf and Bangka Island) as well as, most likely, different diets: in fact, Maniei et al (2020b) acknowledged in their introduction that numerous biotic and abiotic factors influence the chemical composition. To conclude anything about specific differences in metabolites among Peronia based on specimens from only two regions, one of which being represented by a single individual is, to say the least, premature.…”