Molluscs

A total of 342 species of non-marine molluscs were recorded from Germany in the CLECOM list (Falkner et al. 2001; CLECOM 2002) (the subterranean freshwater molluscs are not included here), of which 70 are freshwater and 236 terrestrial species. Twenty freshwater species are considered relicts (glacial or post-glacial isolated). The terrestrial molluscs are represented by 18 relicts.

The relict species include mountain molluscs as well as specialist species at low altitudes, for example in mires, fens and calcareous grasslands. Most relict populations suffer severely from bad environmental conditions. This situation has worsened in recent years because of an intensification of anthropogenic land use.

Table 4 Relict molluscs species in Germany Listed in the Habitats Directive

Species Habitats Conservation status (National Report Art. 17, Hab.

Directive Dir.; Nationaler Bericht 2007) Biogeographic region

Table 4 Relict molluscs species in Germany Listed in the Habitats Directive

Species Habitats Conservation status (National Report Art. 17, Hab.

Directive Dir.; Nationaler Bericht 2007) Biogeographic region

Annex

Atlantic

Continental

Alpine

Snail, Theodoxus transversalis

II, IV

-

Unknown

-

Little Whirlpool Ramshorn

II, IV

Unfavourable

Unfavourable -

-

Snail, Anisus vorticulus

- bad

bad

Freshwater Pearl Mussel,

II, V

Unfavourable

Unfavourable -

-

Margaritifera

- bad

bad

margaritifera

Geyers whorl snail,

II

-

Unfavourable -

Unfavourable -

Vertigo geyeri

bad

inadequate

Round-mouthed whorl snail, II Not evaluated 2007 because thought to be extinct;

Vertigo genesii found again in 2008

Round-mouthed whorl snail, II Not evaluated 2007 because thought to be extinct;

Vertigo genesii found again in 2008

In Annexes II, IV and V of the EU Habitats Directive, 5 of these 18 relicts were represented (Theodoxus transversalis, Anisus vorticulus, Margaritifera margari-tifera, Vertigo geyeri, V. genesii), all of which are represented in the German Natura 2000 network (Table 4). The remaining 13 mollusc relicts mainly live in the following habitat types of Annex I of the Habitats Directive:

• 3110 oligotrophic waters containing very few minerals of sandy plains (Littorelletalia uniflorae)

• 3130 oligotrophic to mesotrophic standing waters with vegetation of the Littorelletea uniflorae and/or of the Isoeto-Nanojuncetea

• 3140 hard oligo-mesotrophic waters with benthic vegetation of Chara spp.

• 3150 natural euthrophic lakes with Magnopotamion or Hydrocharition-type vegetation

• 3260 water courses of plain to montane levels with Ranunculion fluitantis and Callitricho-Batrachion vegetation

• 6210 semi-natural dry grasslands and scrubland facies on calcareous substrates (Festuco Brometalia)

• *6240 sub-Pannonic steppe grassland

• 7140 transition mires and quaking bogs

• 7230 alkaline fens

• 8210 calcareous and calcshist screes of the montane to alpine levels (Thlaspietea rotundifolii)

• 9110 Luzulo-Fagetum beech forests

• 9130 Asperulo-Fagetum beech forests

• *9180 Tilio-Acerion forests of slopes, screes and ravines

• *91E0 alluvial forests with Alnus glutinosa and Fraxinus excelsior (Alno-Padion, Alnion incanae, Salicion alvae)

• 9410 acidophilous Picea forests of the montane to alpine levels (Vaccinio-Piceetea)

This assortment of habitat types and the German Natura 2000 network protects most of the 38 relict species. Only six species which prefer the potamic region of large streams, and Vertigo lilljeborgii, a glacial relict of acid sedge beds, are only partly included in the network. Not only the relict species but also other associated species - such as their specialized predators - should be protected. For example, some local populations of the Pyrenean shell crusher beetle Carabus pyrenaeus are so highly adapted to their prey, the relict mollusc Arianta xatarti, that these populations already show differences in mandible form compared to populations in the Western Pyrenees (Assmann et al. 2000).

Was this article helpful?

0 0

Post a comment