Abstract
Freshwater organisms are facing threats from various natural and anthropogenic disturbances. Using data sampled on a nationwide scale from streams in South Korea, we identified the crucial environmental factors influencing the distribution and abundance of freshwater gastropods. We used nonmetric multidimensional scaling and the random forest model to evaluate the relationships between environmental factors and gastropod assemblages. Among the 30 recorded species, two invasive gastropod species (Pomacea canaliculata and Physa acuta) have enlarged their distribution (10.4% and 57.3% frequency of occurrence, respectively), and were found to be widespread in streams and rivers. Our results revealed that the most influential factor in the distribution of gastropod assemblages was the ratio of cobble (%) in the substrate composition, although meteorological and physiographical factors were also important. However, the main environmental factors influencing species distribution varied among species according to habitat preference and environmental tolerance. Additionally, anthropogenic disturbance caused a decrease in the distribution of endemic species and an increase in the spatial distribution of invasive species. Finally, the results of the present study provide baseline information for planning successful strategies to maintain and conserve gastropod diversity when facing anthropogenic disturbance, as well as understanding the factors associated with the establishment of invasive species.
Highlights
Freshwater gastropods comprise 5% of the global gastropod fauna but are facing a disproportionately high degree of threat according to the 2019 IUCN Red List of Threatened Species [1]
Our results revealed that the most influential factor in the distribution of gastropod assemblages was the ratio of cobble (%) in the substrate composition, meteorological and physiographical factors were important
Results high values of TN, conductivity, BOD, and TP were located on the right side of nonmetric multidimensional scaling (NMDS) 1
Summary
Freshwater gastropods comprise 5% of the global gastropod fauna but are facing a disproportionately high degree of threat according to the 2019 IUCN Red List of Threatened Species (http://www.redlist.org, Cambridge, UK) [1]. 74% of gastropod species have been classified as vulnerable, endangered, threatened, or already extinct in the United States and Canada [2]. In South Korea, two rare species (Clithon retropictus and Koreanomelania nodifila) are listed in the Red Book as endangered, and five species (K. nodifila, Koreoleptoxis globus ovalis, Semisulcospira coreana, Semisulcospira forticosta, and Semisulcospira tegulata) are endemic in the database of the National. These threats are of particular global concern because most freshwater gastropods are endemic with small geographic ranges [2,5,6,7]. Across a large-scale area that includes several basins, climate-related factors, such as
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