Global species richness of hydrobiid snails determined by climate and evolutionary history

Abstract

Efforts to describe spatial patterns of freshwater diversity and to evaluate their underlying factors have traditionally been focused on some animal groups (e.g. amphibians, fish or dragonflies). Despite being a dominant component in continental aquatic ecosystems and crucial for determining priority areas for conservation, broad‐scale data on gastropod total species, endemic and threatened species richness are limited. Based on these biodiversity indices, we identify global hotspots, extinction risk along the elevational gradient and the drivers of species richness patterns in the largest group of freshwater gastropods, the family Hydrobiidae. Given the strong dependency to a nonmarine aquatic environment, the observed richness patterns of extant hydrobiid species could be significantly influenced by large‐scale geography and dispersal processes as well as climatic conditions affecting continental ecosystems. Therefore, we tested several predictions for species richness derived from ecological and evolutionary hypotheses postulated for other freshwater groups. Based on a comprehensive literature and biodiversity database review, we compiled the number of total, endemic and threatened species per freshwater ecoregion. We classified ecoregions as hotspots if each biodiversity index was in the top 25% of its range and assessed the effect of 13 environmental and evolutionary factors on species richness using generalised linear models. We identified 906 species and 157 genera of Hydrobiidae showing mainly a Nearctic–Palearctic distribution and 19 biodiversity hotspots, most located across the Mediterranean Basin. In our data set, 83% of the species were endemic to a single ecoregion. Of the 43% non‐data deficient species, we found almost three times more threatened than non‐threatened species, and extinction risk peaked at 1,500 m a.s.l. Species richness was unequally distributed over biogeographic realms, increased with higher connectivity among ecoregions, and was negatively related with annual temperature range. Latitude and precipitation seasonality explained part of the richness variation by a nonlinear relationship. The identified hotspots correspond with those of other freshwater taxa. The hump‐shaped relationship of extinction risk with elevation is likely the consequence of decreasing natural and anthropogenic perturbations at higher elevations. Global hotspots of Hydrobiidae richness represent areas of climatic stability with medium precipitation and temperature seasonality that are well connected with other hydrological basins. Our results illustrate that both evolutionary and environmental factors determine these global patterns and that future changes of the latter factors may affect hydrobiid richness.

The freshwater snails (Mollusca: Gastropoda) of Mexico: updated checklist, endemicity hotspots, threats and conservation status

“…The Cochliopidae contains by far the highest number of endangered species of all families. This result is consistent with the data from the USA and Canada and the worldwide trend of hydrobioid families being the most imperiled of all gastropod families (Johnson et al, 2013;Miller et al, 2018). In Mexico, of all the 94 imperiled freshwater gastropods, 51 (54.3%) are hydrobioid species.…”

Freshwater molluscs of the Zrmanja and Krupa Rivers (Croatia) – the role of these rivers as a refuge of threatened and endemic species

“…radoMan 1983) or in the whole Balkan region. This area, with its hundreds of endemic species of freshwater molluscs, mainly small hydrobiids, is thus a much more appropriate candidate for an important part of the Balkans, and is ranked as a hotspot of global biodiversity (Griffith et al 2004(Griffith et al , stronG et al 2008 and also as the part of Dalmatia which is one of the most important hotspots of hydrobiid diversity (MiLLer et al 2018).…”

“…The Balkan region holds a rich freshwater fauna and belongs among the world's hotspots of global biodiversity (Griffith et al 2004). Dalmatia is regarded as a global hotspot of hydrobiids (MiLLer et al 2018). Many mollusc species (mostly gastropods) in the region have small, restricted ranges and are only found in small hydrographic systems: rivers, lakes or springs (réGnier et al 2009).…”

Gastropods in Small Water Bodies of the Western Balkans—Endangerments and Threats

“…Freshwater gastropods indicated zoogeographically great diversity and authenticity of investigated area, through the relatively high number of endemic species. There are 11 local endemics on the territory of Serbia (Bythinella drimica alba Radoman, 1976 Globaly, with at least 900 valid species [20], Prosobranchs gastropods from Hydrobiidae family are one of the largest gastropod families. Out of 586 described Hidrobiidae species in Europe, 570 are considered endemic (97%) [18].…”