Multiple Introductions of the Pestiferous Land Snail Theba pisana (Müller, 1774) (Gastropoda: Helicidae) in Southern California

Abstract

The terrestrial land snail Theba pisana is circum-Mediterranean in native range and widely introduced and pestiferous in regions around the world. In California, USA, T. pisana has been recorded intermittently since 1914, but its source population(s) are unknown, and no morphological or molecular analyses within or between California populations have been published. Therefore, we compared molecular data (CO1, 16S, ITS2) and internal morphology (jaw, radula, reproductive system) in T. pisana collected from Los Angeles and San Diego counties in 2019–2020. DNA barcode (CO1 mtDNA) analysis revealed that T. pisana from Los Angeles County was most similar to T. pisana from the Mediterranean island of Malta, and northern San Diego County-collected specimens were most similar to T. pisana from Morocco. Morphology of the jaw and mucous glands also differed between Los Angeles and San Diego populations, but it is unclear if traits are lineage-specific or artifacts of ontogeny. Several pathways of introduction into Southern California are possible for this species, but evidence for intentional vs. accidental introduction of present populations is lacking. Subsequent investigation(s) could use the data generated herein to assess the provenance of T. pisana elsewhere in California and/or worldwide and inform analyses of reproductive biology and systematics in this widespread species.

Annotated and Updated Checklist of Land and Freshwater Molluscs from Asturias (Northern Spain) with Emphasis on Parasite Transmitters and Exotic Species

“…Land and freshwater snails, slugs and bivalves have been introduced unintentionally and intentionally to many regions worldwide [23,24]. These introduced species, when become invasive, have greatly impacts on native biodiversity, i.e., preying upon or outcompeting native species, transferring pathogens and parasites, causing community and ecosystem level imbalances or even facilitating the introduction of other species [9,23,25].…”

The find of six species new to Belgium highlights the role of the stone trade as a pathway for non-native land snails (Gastropoda: Stylommatophora

“…Nevertheless, only T. pisana is reported to have become established in the USA,where the species is ranked as third mollusc in terms of pest potential(cowie et al 2009). Theba pisana was introduced by humans and is widespread in California, the southern UK, Macaronesia, Australia, southern African countries and countries around the Red Sea(Däumer et al 2012;venDetti et al 2021;EPPO 2023). Theba pisana has also been sporadically found in Helgoland (Germany), Finland, the Democratic Republic of Congo, and, for Belgium, in inland Flanders and in Brussels (wiese 2014; https://www.inaturalist.org/observations/92097501; kayeye et al 2014; http://observations.be).…”