Table 2. Characteristics of the sampling sites including the number of clams genotyped (N), observed (H_O) and expected (H_E) heterozygosity and the genetic effective population size (Ne estimate) with the lower (lower CI) and the higher (higher CI) confidence intervals.

	N	Ho	He	Ar	Ne estimate	lower CI	higher CI	Situation*
Isla Canela	85	0.533	0.799	14.327	210	165.1	238.6	at high long-term risk of extinction
Doñana	86	0.517	0.817	14.689	1191.7	526.9	∞	at evolutionary potential
Caleta de Vélez	56	0.516	0.773	13.109	782.5	320	∞	at high long-term risk of extinction
Cabo de Gata	86	0.463	0.826	13.573	357.2	245	635.6	at high long-term risk of extinction
Gandía	53	0.468	0.769	12.577	332.5	203.3	845.1	at high long-term risk of extinction
Sant Carles de la Ràpita	62	0.423	0.758	11.136	602.7	282.9	∞	at high long-term risk of extinction
Roses	86	0.486	0.756	15.202	600.3	340.4	2210.8	at high long-term risk of extinction

The use of ∞ indicates inestimable upper confidence limits* ⁵⁶.