Molecular phylogenetics and systematic revision of the south-eastern Australian Helicarionidae (Gastropoda, Stylommatophora)

Abstract

The south-eastern Australian helicarionid clade currently comprises six genera of snails and semislugs united by genital characters, including an epiphallic flagellum that produces a spiraling, spinose spermatophore, the absence of an epiphallic caecum, and the presence of at most a very short vagina. We comprehensively revise the taxonomy of this group based on comparative analyses of key morphological features and mitochondrial markers COI and 16S, revise the placement of several species described recently on the basis of shell morphology alone, and describe new taxa. The snail genus Brevisentis is monophyletic as currently understood, but includes an additional undescribed species from Wollemi National Park, New South Wales. Mysticarion is shown to contain four arboreal semislugs with wide, disjunct ranges, including one new species (Mysticarion obscurior sp. nov.). We synonymise Fastosarion staffordorum with Mysticarion hyalinus. The semislug Desidarion is synonymised with Parmavitrina, and we describe two new species of this genus, P. flavocarinata sp. nov. and P. maculosa sp. nov. The semi-arboreal semislug Cucullarion is herein included in the south-eastern Australian helicarionid clade based on morphological and genetic evidence, despite its more northerly distribution. Two small semislugs so far placed in Peloparion do not group together and a new genus, Ubiquitarion gen. nov., is described for Peloparion iridis. All of these genera, together with the semislug Helicarion (not included here), form a monophyletic radiation endemic to southeastern Australia.

Lessons from Timor: Shells are poor taxonomic indicators in Asperitas land snails (Stylommatophora, Dyakiidae)

“…Although genetic distances per se are poor taxonomic indicators (Dasmahapatra et al, 2010;Davison et al, 2009;Köhler, 2007;Köhler & Johnson, 2012), the maximum distances between any two Asperitas samples were well within the range of intraspecific mitochondrial differentiation in the closely related genus Everettia from Borneo (Liew et al, 2009; Figure 2). These distances are also comparable with the amounts of intraspecific genetic distances recently observed in several helicarionid genera from Australia belonging to the same superfamily (Hyman & Köhler, 2018, 2019Hyman et al, 2017) as well as in other stylommatophorans (for an overview of intra-and interspecific COI distances in various stylommatophoran groups refer to Koch et al 2020; Table S3). Moreover, our examinations revealed that the reproductive anatomy in individuals from Timor, Bali, and Flores, which represent several nominal species, was virtually identical.…”

Feeling sluggish: The extreme semislugs of Australia (Stylommatophora,Helicarionidae)

“…There are several genital characters that are seen in all or most of the extreme helicarionid semislugs. All five genera examined herein, and additional extreme semislug genera Parmellops and Cucullarion , have a unilobed ovotestis and lack a vagina (Hyman et al, 2017; Hyman & Ponder, 2016). The only exceptions are Thularion semoni and T. stanisici , which have a distinct vagina.…”

Attenborougharion gen. nov. (Mollusca: Pulmonata: Helicarionidae): a likely case of convergent evolution in southeastern Tasmania

“…DNA extraction, PCR and sequencing were undertaken as described by Hyman et al (2017). Electropherograms were corrected for misreads and forward and reverse DNA strands were merged into one sequence file using CodonCode Aligner v. 3.6.1 (CodonCode Corp., Dedham, MA).…”

“…Electropherograms were corrected for misreads and forward and reverse DNA strands were merged into one sequence file using CodonCode Aligner v. 3.6.1 (CodonCode Corp., Dedham, MA). Sequences of previous helicarionid studies (Hyman et al, 2007;Hyman et al, 2017) were retrieved from GenBank and included in our dataset while all newly produced sequences have been deposited in GenBank under the accession numbers KY769386-KY769398.…”

“…The Helicarionidae is a family of land snails in which about half of all species have evolved a reduced, ear-shaped shell into which they cannot fully retract (i.e., they have evolved into so-called semislugs). The type genus of the family, Helicarion Férussac, 1821, is part of a monophyletic radiation that is restricted to southeastern Australia and includes six additional genera (Mysticarion Iredale, 1941, Parmavitrina Iredale, 1937, Cucullarion Stanisic, 1998, Peloparion Iredale, 1937, Ubiquitarion Hyman, Lamborena & Köhler, 2017 and Brevisentis Hyman, 2007), all of which have recently been revised comprehensively (Hyman & Ponder, 2010;Hyman, Lamborena & Köhler, 2017). This clade is supported by several morphological synapomorphies, including the presence of a spiralling, spinose spermatophore, a flagellum with internal cryptae, at most a very short vagina, and the absence of an epiphallic caecum.…”