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Tomasello, Di Maida, Calvo, Pirrotta, Borra & Procaccini Seagrass meadows at the extreme of environmental tolerance

Table 1. Parameters of genetic variability. N = number of samples with a complete multilocus genotype, no missing data; MLG = Multi Locus
Genotypes; MLL = Multi Locus Lineages; clonal diversity (R) and number of alleles (A) for the entire sample and for the subset of 16 ramets
obtained after 1000 permutations (R16 and A16); %pl = percent of polymorphic loci; pA = private alleles; Fis = inbreeding coefficient; Hexp = ex-
pected heterozygosity; Hobs = observed heterozygosity.

N MLG MLL R R16 % pl A pA A16 Fis Hexp Hobs

Atolls 39 32 31 0.79 0.88 ± 0.03 77 36 1 32.28 ± 0.04 )0.44 0.36 0.52

Re´ cif 33 31 31 0.94 0.97 ± 0.02 100 48 4 45.05 ± 0.05 )0.08 0.50 0.55

Plateau 16 16 16 1.00 – 100 48 3 – )0.02 0.50 0.53

Nubia 38 38 38 1.00 1.00 ± 0.00 100 52 6 42.29 ± 0.06 )0.14 0.45 0.52

Marsala 35 35 35 1.00 1.00 ± 0.00 92 47 5 41.76 ± 0.04 )0.21 0.51 0.62

Favignana 40 40 40 1.00 1.00 ± 0.00 100 46 2 42.02 ± 0.05 )0.15 0.56 0.65

(Atolls) to 0.56 (Favignana) and from 0.52 (Atolls and Fig. 2. Kinship coefficients (Loiselle et al. 1995) of spatial autocorre-
Nubia) to 0.65 (Favignana). An excess of heterozygotes
was detected in all six sites (Hobs > Hexp). The highest lation measured for the Atolls site. Upper (CI-sup) and lower limits
difference was recorded in the Atolls (Table 1). The
inbreeding coefficient (Fis) was also lower in the Atolls (CI-inf) of the 95% confidence intervals are also shown.
site (Table 1). Replicated genotypes (clones) did not have
higher number of heterozygous loci with respect to geno- correlation in all the sites outside the lagoon was positive
types represented by only one individual. up to about 40 m. The coefficient of determination (r2)
was higher in the Atolls (r2 = 0.569) and in the Re´cif
Potential linkage at some loci was present in all popu- (r2 = 0.198) than in the other populations (Plateau,
lations but the number of such loci was consistently r2 = 0.07; Nubia, r2 = 0.018; Marsala, r2 = 0.037; Favig-
higher in the two Stagnone populations (Atolls and Re´cif) nana, r2 = 0.009). The slope was the highest in the Atolls
than in the others. (b = )5 · 10)4, P < 0.001) and the lowest in Favignana
(b = )5.6 · 10)5, P = 0.033). The value was comparable
The lowest number of alleles (A = 36) was also (b = )1 · 10)4) for the other four populations (Re´cif,
detected in the Atolls (Table 1). Moreover, at the same P < 0.001; Plateau, P = 0.019; Nubia, P = 0.009 and Mar-
site, the lowest value of polymorphic loci was recorded
(77%) as opposed to an average value of 98.4% in the sala, P < 0.001).
remaining five sites. Ranking of allelic richness and geno-
typic richness values did not change after 1000 subsam- Gene flow among sites
plings of 16 ramets per population.
The highest pairwise values of Fst were recorded between
There was a greater similarity in the distribution of Atolls and all the other sites (> 0.1) except for the Re´cif,
allelic frequencies between Atolls and Re´cif than between in which the value was 0.075 (Table 2). Fst values among
these two and the sites outside the lagoon (the table of
allele frequency is available from the authors upon Table 2. Pairwise Fst values for the six sites considered in the analy-
request). Indeed, the alleles Po5-40.224, Po15.153 and ses.
Po15.155 are almost exclusively present in the Atolls and
Re´cif sites. The comparison of the two sites of the Stag- Atolls Re´ cif Plateau Nubia Marsala Favignana
none shows some differences between the genotypes pres-
ent in the southern sub-basin (Re´cif) and those in the Atolls 0.000 0.000 0.000 0.000 0.000 0.000
innermost site (Atolls). In the Atolls, some alleles are Re´ cif 0.075 0.050 0.041 0.060 0.057
fixed (i.e. Poc-trn.316, Poc-35.200 and Poc-26.316). For Plateau 0.164 0.036 0.041 0.041
other alleles, either a negative or a positive trend in Nubia 0.105 0.065 0.048
frequency can be noticed moving from more to less Marsala 0.181 0.057
confined areas inside the lagoon (e.g. Po5.182 and Favignana 0.136
Po5-49.240).

The number of private alleles was low, with the highest
value in Nubia (6; Table 1). Surprisingly, the two sites
inside the lagoon had fewer private alleles relative to
external ones (5 versus 16).

Spatial autocorrelation was significant up to slightly
below 300 m in the Atolls and Re´cif sites (Fig. 2). Auto-

Marine Ecology 30 (2009) 288–300 ª 2009 Blackwell Verlag GmbH 293