Barcoding of South African forest‐dwelling snails (Mollusca: Gastropoda) reveals widespread cryptic diversity

Abstract

South Africa harbors a rich and diverse terrestrial snail fauna. Despite their importance in ecosystem functioning and structure, their alpha taxonomic diversity is poorly understood, and most groups have not been the subject of molecular systematic scrutiny. During the present study, we used the mitochondrial cytochrome c oxidase subunit I (COI) locus to start a DNA barcode reference library, to examine intra-and interspecific genetic divergence, and to explore the presence of cryptic diversity among terrestrial gastropods from forested regions in the country. We generated 399 COI barcodes comprising 70 morphospecies in 26 genera and 15 families, representing nearly 10% of the described gastropod diversity in South Africa. Our results showed a substantial overlap between mean intraspecific and interspecific genetic variation and no barcoding gap. Three species delimitation methods-Poisson Tree Processes (PTP), Refined Single Linkage (RESL) algorithm in Barcode of Life Data Systems, and the Automatic Barcode Gap Discovery (ABGD)-applied to selected widespread species retrieved incongruent operational taxonomic units (OTUs). These results, coupled with high intraspecific variation, suggested cryptic diversity among several terrestrial gastropod genera in the country. We further demonstrated that DNA barcoding analysis holds the potential for highlighting cryptic lineages in snails and for revealing taxa in need of taxonomic revision. We recommend that future taxonomic studies of South African terrestrial snails incorporate multiple sources of information for species delimitation.

Genetic diversity of a short‐ranged endemic terrestrial snail

“…Studies using mtDNA have long been the mainstay for terrestrial SREs and have proven to be critical for assessing long‐term evolutionary patterns, such as allopatric differentiation driven by low dispersal ability in groups such as amphipods (Menz et al., 2016) and beetles (Papadopoulou et al., 2008), and for examining the relationships between landscape and population structure (Garrick et al., 2012). In addition, mtDNA studies have proven critical for the detection of cryptic species in SREs (Raphalo et al., 2021). On the other hand, SNP analyses have proven effective in detecting fine‐scale population genetic differentiation and can provide a more detailed analysis of gene flow between populations (McGaughran et al., 2019).…”