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INTRODUCTION
All around the planet the endangered species are precipitately disappearing as direct or
indirect result of the anthropization. The use of fossil fuels and deforestation has
increased over the Iast three centuries the concentration of carbon dioxide (C02) by
30%; other human activities have doubled the concentration of methane and increased
the concentration of other gases involved in global warming. The expansion of urban
and agricultural areas has incorporated grasslands, forests and wetlands pouring into
water basins increasing amounts of water nutrients, responsible for changes at
ecologicallevel of estuarine and coastal ecosystems.
In marine environment, three-quarters of harvested fish populations monitored by the
FAO are already overexploited, or will become so without stringent management
intervention (Ba1mford et al., 2005; FAO 2000). Indeed the introduction of aggressive
alien species are giving the final j ab to exhausted natura] (eco)systems. Incontrovertible
evidences of the ongoing loss of biodiversity can be found looking at The Red List of
Threatened Species, redacted by the Intemational Union for Conservation ofNature
(IUCN) that documents the extinction risk of 47,677 species: 17,291 are threatened,
including 12% of birds, 2 1% of mammals, 30% of amphibians, 27% of reef-building
corals, and 35% of conifers and cycads. The Living Planet Index reveals that
populations of wi ld species have declined by 30% since 1970; mangrove forests have
Iost a fifth of their area since 1980, and 29% of seagrass beds are gone (Marton-Lefèvre,
2006).
In marine environment the biodiversity is also threatened by the inaccurate
ascertainment to consider it an environment with high phyletic but low specific
diversity, inhabited by few, wide ranging species, but where unrecorded majority

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Gìan Luca Dedola: ANALISI DELLA VARIABILITÀ GENETICA DI PATELLA FéRRUGINEA, PATEL-LA UL l'SSIPONENSIS (MOLLUSCA: GASTROPODA) E PINNA
NOBILIS (MOLLUSCA: BIVALVIA): lLCONTRJBUTO DEl DATI MOLECOLARl ALLA CONSERVAZIONE DI SPECIE MINACCIATE - Tesi di douorato in Scienze
della natura e delle sue risorse · indiri7.zo BK>logi.a Ambientale, Università degli Studi di Sassarl