Table 3. Genetic variability of the three species studied
% p. n. of alleles b H.bo C H d
"' "
Orchestia gammarella
26.7
Orchestia mediterranea 40.0
Orchestia montagui
23.5
1.4
1.5
1.3
0.089 0.0082
0.070 0.072
0.036 0.056
• Percentage of polymorphic loci with 95% criterion
b Average number of alleles scored
C Observed heterozygosity
d Expected heterozygosity under the Hardy-Weinberg equilibrium
hypothesis
O. gammarella
O. mediterranea
O. montagui
- d = 0.2
Biodiversity in Beach Fleas
395
larity in morphology and the sympatric occurrence, represent highly differentiated evolutionary units.
High genetic divergence between species was
confirmed by RAPD-PCR analysis. In fact, RAPD
patterns were highly species-specific (Fig. 2) for
all the primers used. Not one of the about 130
RAPD markers amplified in each species was reliably scored in the other two. Moreover, some
monomorphic bands were scorable with high
confidence. due to the lack of any co-migrating
Fig. 1. Nei genetic distance between the three
Orchestia species studied, and diagnostic
Gnathod of the male
OPA09
OPA 10
OPA 16
MI ) 1 2 3 4 5 6 7 8 9)1 2 3 4 5 6 7 8 9)1 2 3 4 5 6 7 891M
Fig. 2. Examples of RAPD phenotypes with three different decamer primers (OPA09 - OPAIO - OPA16) in Orchestia montagui
(1,2,3), O. mediterranea (4,5,6) and O. gammarella (7,8,9). (M, Molecular marker)