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of them are vanishing before their existence, much less their biologica! importance or
economie utility, is established (Eckholm, 1978).
A significant difficulty to appreciate the levels of marine biodiversity arises not only
because the number of described species falls far short of actual diversity (Blaxter,
2004), but also because species are often exceedingly difficult to recognize using
morphological approaches, as an important hidden source of diversity in marine systems
lies in cryptic species complexes - species that are difficult to distinguish
morphologically (Mayr, 1963) - which are common in marine groups and may be
important and underestimated components ofthe ecosystem (Knowlton, 1993, 2000).
In spite of "sins of mankind" ali these species now require human assistance to improve
their chances of survival and population recovery, outstandingly, the conservation of
natura! populations directly in their originai environment need to assess the genetic
resources that are really available and to investigate the evolutionary mechanisms that
regulate their maintenance. Genetic factors make important contributions to extinction
risk, for these reasons they require an appropriate management.
Conservation genetics encompasses genetic management ofthese threatened
populations, resolution of taxonomic uncertainties and the use of molecular tools
(Frakham, 2003) in order to study genetic pattems or processes that informs
conservation efforts (Avise, 2008).
Not all the genomic regions show identica! potential in depicting population dynamics
of species. Different levels of evolutionary patterns could be only pointed out by means
of molecular markers with different specific prerequisites. Genes coding for proteins
essential for life generally tend to slowly fix mutations being useful for reconstruction
ofphylogeny at higher taxonomic level. Conversely, non-coding regions and DNA
portions of poor biologica! interest, accumulating mutations with neutra! value, are

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Gìan Luca Dedola: ANALISI DELLA VARIABILITÀ GENETICA DI PATELLA FéRRUGINEA, PATEL.LA ULl'SSIPONENSIS (MOLLUSCA: GASTROPODA) E PINNA
NOBILIS (MOLLUSCA: BIVALVIA): lLCONTRJBUTO DEl DATI MOLECOLARI 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