Abstract
The aquatic snail genusDianella(Gastropoda: Hydrobiidae) has only two representatives in Greece:DianellaschlickumiSchütt, 1962 andDianellathiesseana(Kobelt, 1878).D.schlickumi, a narrow endemic species to Lake Amvrakia (in Aitoloakarnania, western-central Greece), is considered as Critically Endangered (Possibly Extinct, sensu IUCN 2017). Our study confirmed its presence in Lake Amvrakia, where it had not been detected for more than 30 years. We document the unknown anatomical characters based on theD.schlickumispecimens. Moreover, the presence ofD.thiesseanain the nearby lakes Trichonis and Lysimachia was also confirmed, while morphometric analyses enabled the discrimination between the two species. Redundancy Analysis revealed conductivity, dissolved oxygen and pH as the main environmental variables related to the above species’ distribution, shaping their community structure. BothDianellaspecies require urgent conservation measures to be enforced, due to their habitat degradation from human activities, which are limiting and fragmenting their range. For that purpose, effective management plans have to be elaborated and implemented at the mentioned lakes, focusing on the reduction of human pressures and on the improvement of their habitats.
Highlights
Freshwater habitats cover less than 1% of the earth’s surface, but they support almost 10% of the known species on the planet (Strayer and Dudgeon 2010)
Dianella schlickumi was found at the south-east part of Lake Amvrakia, in 5 (S7, S11, S12, S13, S14; Figure 1) out of the 14 stations (36%) surveyed, at depths ranging from 5 m to 13 m
The presence of a live D. thiesseana was confirmed in the east side of Lake Lysimachia by surveys executed during the National Water Monitoring Programme in spring 2015 (Mavromati, personal communication)
Summary
Freshwater habitats cover less than 1% of the earth’s surface, but they support almost 10% of the known species on the planet (Strayer and Dudgeon 2010). The rich fauna of freshwater molluscs is considerably threatened (Albrecht and Wilke 2008) and 29 species of the Balkan Peninsula have already become extinct (Régnier et al 2009), representing 21% of the 140 known extinctions of freshwater mollusc species worldwide In this region, many endemic gastropod species exist with a restricted range only extending to small hydrographic systems (rivers, lakes and springs). The karst landscape, which occurs in a large proportion of the Balkan Peninsula, contributes to this high degree of endemism (Régnier et al 2009) These species are vulnerable due to habitat degradation caused by human activities, and by their very limited range, which increases the risk of accidental extinction (Régnier et al 2009). For Greece, a similar crucial decline of population densities and losses of some endemic mollusc species have been reported (Albrecht et al 2006), suggesting the necessity for urgent actions for their conservation
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