Freshwater mollusc biodiversity and conservation in two stressed Mediterranean basins

Abstract

a b s t r a c tThis paper reviews the environmental factors that influence biodiversity of freshwater mollusc communities and conservation status of watercourses in two Mediterranean acid mine drainage-impacted basins of the southern Iberian Peninsula. We found 17 mollusc species: 14 gastropods (10 native and 4 introduced) and 3 bivalves. We found five distribution patterns: native headwater (Arganiella wolfi, Stagnicola palustris, Unio delphinus, Pisidium casertanum and Pisidium personatum) and mouth (Hydrobia acuta, Peringia ulvae and Myosotella myosotis) sensitive-stenochoric species, intermediate sensitive-widely distributed species (Planorbarius metidjensis and Radix balthica), insensitive-eurychoric species (Ancylus fluviatilis), and erratic-distribution pattern species (Galba truncatula and Planorbis carinatus). The highest biodiversity indices have been found in non-impacted headwaters and, to a lesser extent, in tidal streams. The biodiversity of the middle reaches, with varying degrees of impact by acid mine drainage and high water deficit, was scarce and dominated by introduced species. Over 30% of the variation in native and introduced species richness is explained by environmental gradients related to heterogeneity (instream macrophytes cover and Fhi and Qbr indices) and acid runoffs (pH, conductivity, turbidity and concentration of sulphides). Severely impacted sites have no mollusc species. The conservation status of watercourses is also very remarkably influenced by the heterogeneity and contamination of the environment. Conservation values are higher in water bodies located in protected northern and southern sites in both basins.

First evidence of asymmetric competition between the non‐native clam Corbicula fluminea and the native freshwater mussel Unio delphinus during a summer heat wave

“…The freshwater mussel Unio delphinus Spengler, 1783 is an endemic species from western Iberian basins, such as the Miño, Douro, Tajo, and Guadiana (Froufe et al, ; Morais, Rufino, Reis, Dias, & Sousa, ; Pérez‐Quintero, ; Reis, Machordom, & Araujo, ). It is listed as ‘Near Threatened’ in the International Union for Conservation of Nature (IUCN) Red List (Araujo, ) as it has been declining in abundance and in spatial distribution over the last four decades (Araujo, ; Araujo et al, ).…”

Negative effects of Corbicula fluminea over native freshwater mussels

“…The freshwater mussel Unio delphinus Spengler, 1783 is an Iberian endemism from western basins such as Miño, Douro, Tajo, and Guadiana, among others (Pérez-Quintero, 2011;Reis et al, 2013;Morais et al, 2014;Froufe et al, 2016). This species is listed as near threatened by the IUCN Red List (Araujo, 2011).…”

Distribution patterns of freshwater molluscs along environmental gradients in the southern Guadiana River basin (SW Iberian Peninsula)

“…Whereas the effect of microhabitat and macrohabitat descriptors on the distribution of Mediterranean freshwater macroinvertebrates, sensu lato, have received substantial attention and has been widely demonstrated (Gallardo et al, 1994;Vitor et al, 2002;Beauchard et al, 2003;Arab et al, 2004;Graça et al, 2004;Chaves et al, 2005;Bonada et al, 2006aBonada et al, , b, 2007Sánchez-Montoya et al, 2007), few such investigations have been conducted on freshwater molluscs as surrogates of biodiversity in freshwater Mediterranean streams (Pérez-Quintero, 2007, 2011.…”

“…As a result of reduced flow during the waterstress period, active dispersers, for example winged freshwater arthropods, are more likely to find suitable sites (Bilton et al, 2001;Rundle et al, 2002;Green & Figuerola, 2005) than other macroinvertebrates with low capacity for movement, for example freshwater molluscs. Therefore, the temporary cessation of water flow implies that mollusc communities are more prone to local extinctions caused by seasonal drought (Lodge et al, 1987;Pérez-Quintero, 2011), by predators (Nystrom et al, 1999;McRae et al, 2004) and, even, by changes in environmental variables because of climate change (Mouthon & Daufresne, 2006).…”