Page 13 - Capula1994

186 M. CAPULA

P. wagleriana populations from Sicily (P = 0. 15; Ho= 0.037) and the Aegadian

Islands (P= O. l 7; Ho = 0.049) were similar both to the average ones calculated

by Nevo (1978) for 17 species of rep ti les (P = 0.22; H = 0.047), and the average
0 Ho =
ones calcul ated by Capula ( 1990} for n i ne species (P = 0.13;
of Podarcis

0.053). The Aeolian samples of P. wagleriana showed ooticeably lower values of

polymorphism and hetcrozygosity (P = 0.05; H = 0.0 l l ). The severe reduction
0

in genetic variability poin ted oul in rhese samples could be due either to geneti c

d rift phenomena or strong directional selection, as sup ported by the fact that

three out of four populations of P. wagleriana known to occur in the Aeolian

Archipelago inhab it ciny volcanic isla nds (Strombolicchio, Scoglio Faraglione,

La Canna), each characterized by a very limi ted area ( < 0.02 km1).

Unfortunately, the p resent data do not permit us to distinguish between the drift

and selection hypotheses.

The levels of polymorph ism and heterozygosi ty are below the mean for the

species of reptiles analysed by evo ( 1978) and Capula ( 1990} (see above) also

in tbe samples of P. sicula (P = 0.06; Ho= 0.01 3). In th e case of P. sicula

popula tions inbabiting satellite island s, however, che observed low geneùc

variabil ity could be due to founder effects (sensu 11ayr, 1982; Barton &

Charlcsworth, 1984), the Aeolian and Acgadian populations of the species

proba bly h aving origi nated from epi odes of acciden tal anthropogenic

introductio n in protohistorical or historical times (Lanza, 1973; Capula et al. ,

1987; Capula, 1990) (see Discussion).

PQpulalion helerogeneiLJ'

The mean FsTamong Sicilian and Aegadian populations of Podarcis wagleriana
was 0.153 (T able 6). Five of the l O single-locus fST values were sta tistically

significa nt, suggesting some genetic differen tiatìon among populations.
However, it must be stressed th at ldh-1 had a much higher Fs,. th an aHother loci.

If this locus is removed because of possible scoring errors, thc mean FsT reduces

to 0.113. M ean f'sT values are also given for aH P. wagleriana samples and the

Total (P. wagleriana plus P. sicula ) (T able 6). Adding the Aeolian samples of
P. wagleriana increases the FsT to a very h igh leve) {0.625 ), suggesting that the

Aeolian popula tions are highly differenti a ted from both the Sicilian and

Aegadian ones. lncluding the popula tìons of P. siwla increases Fsr (0.872)

funh er, indicating that the latter species is genetically quite d ifferen tiated from
P. waglen'ana. F.s values remain low regardless of which pop ulations are in cluded ,
presumably because H ardy-Weinberg p roportioos are maintaincd within

populations by random maring.

The valu es of Nei,s genetic id en ti ty and genetic disrance for each pairwise
com parison are shown i n T able 7. A high genetic homogeneity was fou nd within
P. sicula. Thc values of Nci,s sta ndard genetic distance observcd betwcen the
populations of this specìes ranged from D= O to D= 0.035 (average D =
0.0 15). The Aeolian populations of P. sicula (Filicudi and Salina) were

genetically very si milar to each other and to those from Sici1y and the Aegadian
Islaods (average D= 0.012 ).

As reported above, the lizards from Scoglio F araglione and La C.anna, though

currently assigned to P. sicula (Henle & K\aver, 1986), were found to be

genetically highly differen tiated from all otber populations of this species