Spatiotemporal patterns of non-native terrestrial gastropods in the contiguous United States

Abstract

The contiguous United States (CONUS) harbor a significant non-native species diversity. However, spatiotemporal trends of some groups such as terrestrial gastropods (i.e., land snails and slugs) have not been comprehensively considered, and therefore management has been hindered. Here, our aims were to 1.) compile a dataset of all non-native terrestrial gastropod species with CONUS occurrence records, 2.) assess overarching spatiotemporal patterns associated with these records, 3.) describe the continental origin of each species, and 4.) compare climatic associations of each species in their indigenous and introduced CONUS ranges. We compiled a georeferenced dataset of 10,097 records for 22 families, 48 genera, and 69 species, with > 70% of records sourced from the citizen science database iNaturalist. The species Cornu aspersum Müller, 1774 was most prevalent with 3,672 records. The majority (> 92%) of records exhibit an indigenous Western European and Mediterranean distribution, with overlap in broad-scale climatic associations between indigenous and CONUS ranges. Records are most dense in urban metropolitan areas, with the highest proportion of records and species richness in the state of California. We show increased prevalence of non-native species through time, largely associated with urbanized areas with high human population density. Moreover, we show strong evidence for a role for analogous climates in dictating geographic fate and pervasiveness between indigenous and CONUS ranges for non-native species.

The introduction of the European Caucasotachea vindobonensis (Gastropoda: Helicidae) in North America, its origin and its potential range

“…The discovery of the introduction of C. vindobonensis in North America and the documentation of its spread demonstrates the increasing importance of community scientists in biodiversity monitoring efforts (Vendetti et al 2018;Gladstone et al 2020). The human resources gained with a community scientist platform such as iNaturalist can be essential to detect introduced species early, before they cause damage to the ecosystem, and to track their spatial distribution (Crall et al 2010).…”

“…The colonization of North America by Europeans coupled with its comparatively depauperate native mollusc fauna may have favoured the introduction of a large number of European land snail species, especially those adapted to anthropogenic habitats. Gladstone et al (2020) listed 69 introduced land snail species for which georeferenced occurrence data from the contiguous United States are available. The native ranges of 45 of these 69 introduced species are in Europe; eight additional species have a broad Mediterranean distribution that encompasses Western Europe and Northern Africa (Gladstone et al 2020).…”

“…Gladstone et al (2020) listed 69 introduced land snail species for which georeferenced occurrence data from the contiguous United States are available. The native ranges of 45 of these 69 introduced species are in Europe; eight additional species have a broad Mediterranean distribution that encompasses Western Europe and Northern Africa (Gladstone et al 2020). In contrast, only 11 of the 2480 European land snail species are introduced (Neubert et al 2019).…”

“…In contrast, only 11 of the 2480 European land snail species are introduced (Neubert et al 2019). The number of introduced land snail species in the contiguous United States increased approximately linearly from two around 1900 to the 69 currently recorded species (Gladstone et al 2020). Recently, community science projects have also contributed to the documentation of newly introduced land snail species and their spread (Vendetti et al 2018).…”

Distribution of Phasmarhabditis (Nematode: Rhabditidae) and Their Gastropod Hosts in California Plant Nurseries and Garden Centers

“…The United States harbors a significant diversity of invasive species ( Pimentel et al, 2005 ). They serve as a threat to the country’s natural biodiversity since the introduction of invasive species is one of the leading causes of global biodiversity decline ( Mckinney and Lockwood, 1999 ; Clavero and Garcia-Berthou, 2005 ; Butchart et al, 2010 ; Gladstone and Bordeau, 2020 ). While the distribution of numerous invasives have been tracked, some taxonomic groups have been largely neglected, notably terrestrial gastropod species, many species of which are of agricultural and horticultural interest ( Barker, 2002 ; Pyšek et al, 2008 ; Lowry et al, 2012 ; Gladstone and Bordeau, 2020 ).…”