A misinterpreted disjunction: the phylogenetic relationships of the North African land snail Gyrostomella (Gastropoda: Stylommatophora: Helicidae)

Abstract

The North African helicid Gyrostomella has been considered closely related to Levantina, suggesting a disjunct distribution with a distribution gap of almost 2000 km in North Africa. We studied this disjunction and the systematics of Helicinae using molecular markers. Our analyses indicate an affiliation of Gyrostomella with the radiation of Helicinae in the Maghreb, especially with Maurohelix. The occurrence of Gyrostomella in Libya does not represent a western outpost of Helicini in North Africa, but an eastern outpost of the Maghreb radiation of Helicinae. The disjunction of Gyrostomella in Libya and Maurohelix in Algeria may be the result of a long-distance dispersal or may represent relicts of a larger range of the lineage in the past as a consequence of aridification processes in North Africa. Taking into account biogeographic patterns, we suggest a subdivision of Helicinae into four tribes: Allognathini, Helicini, Maculariini trib. nov. and Thebini. The Eastern Mediterranean Helicini diverged from the Western Mediterranean clade in the Eocene. The Western Mediterranean clade then split into Allognathini in the Iberian Peninsula, Maculariini in the region of the future western Alps and Thebini on terranes probably including the Rif-Betic and Kabylies blocks that now form part of the Maghreb region.

Phylogeny of the land snail Levantina reveals long‐distance dispersal in the Middle East

“…We sequenced c. 810 bp of the 16S rRNA (16S) gene and 655 bp of cytochrome c oxidase subunit I (cox1) gene, the two mitochondrial loci most used in land snail systematics. The laboratory methods used for DNA extraction, PCR and sequencing corresponded to those given in Neiber et al (2021). The primer pairs 16Scs1 + 16Scs2 (Chiba, 1999) and LCO1490 + HC02198 (Folmer et al, 1994) were used for amplification of 16S and cox1 fragments, respectively.…”

“…The first 10,000,000 generations were discarded as burn-in. The root was assumed to be between a distinctively divergent Levantina lineage from near Lake Van and the rest of the samples as suggested by the analysis of Neiber et al (2021).…”

“…The phylogenetic relationships of Levantina to the other Eastern Mediterranean rock-dwelling Helicini, namely Neocrassa Subai, 2005, Codringtonia Kobelt, 1898, Isaurica Kobelt, 1901, and Amanica Nordsieck, 2017, remain unresolved (Neiber et al, 2021. Neocrassa and Amanica are narrowly distributed (Subai, 1994(Subai, , 2005 and isolated (Neiber et al, 2021) monotypic genera. Isaurica has a limited range in the south-west of Anatolia (Subai, 1994).…”

“…Most of the species currently included in the genus were placed into a separate genus Assyriella Hesse, 1908(Hesse, 1918Schütt & Subai, 1996;Subai, 1994). This arrangement has been overturned by Neiber et al (2021), who demonstrated that Gyrostomella actually belongs to a different tribe of Helicinae and both the subgenera Levantina and Laevihelix are nested among species assigned to Assyriella. Laevihelix and Assyriella are, therefore, now both considered junior synonyms of Levantina.…”

“…The study of Levantina has been always plagued by a scarcity of material from most of its large range, which to this day prevents a thorough phylogenetic and taxonomic analysis of the genus. However, we were recently able to revise the delimitation of the genus by excluding the North African Gyrostomella and synonymising Assyriella and Laevihelix with Levantina, thanks to the utilisation of museum specimens (Neiber et al, 2021).…”