Page 12 - 5(1)_39-54

50 SALVATORE PASTA ET ALII

DISCUSSION

Phytogeographical insight on the local va-
scular flora

The 73 terrestrial vascular plants recorded on the 10
four considered islets belong to 28 different families
(the most represented being Asteraceae, Poaceae 11
and Amaranthaceae with 12, 11 and 6 infrageneric
taxa, respectively) and 62 genera. If we consider ab- 12
solute values, the richest islet is PRE with 46 taxa,
followed by FLE (32), while both GAL and ROT Figure 10. Life-form spectrum of the vascular flora of each
host only 11 species. A simplified analysis of islet. Figure 11. Chorological spectrum of the vascular flora
species/area relationship seems to separate the most of each islet. Figure 12. average values of Ellenberg indica-
isolated islets from those that are near to the main tors concern-ing the vascular flora of each islet.
islands. In fact, the value of the rate nr taxa/m2 is
0.011 and 0.015 for PRE and GAL, respectively, birds which occasionally feed on it according to
while it is 0.026 for ROT and 0.033 for FLE. Sarà & Zanca (1988) and Siracusa & Lo Duca
(2008), respectively. As the western coast of Sicily
Although the striking differences concerning seems to be too far away from PRE, future in-
both the life-form spectrum (e.g. stark prevalence vestigations on its occurrence should start from
of therophytes only on PRE and GAL, high vari- Favignana.
ability of the percentage of chamaephytes, total ab-
sence of hemicryptophytes in GAL and ROT: Fig.
10) and the chorological spectrum (e.g. absolute
dominance of Mediterranean taxa only on FLE: Fig.
11) are still unexplained, this is not such a rare pat-
tern on the very little islets, which often represent
‘unbalanced biota’.

As for Ellenberg bioindicators values (Fig. 12),
only R show some significant - and yet unexplained
- variation between PRE e GAL (very high) and
FLE (very low).

Although no real islet specialists have been de-
tected, it should be underlined that the only two taxa
whose presence has been recorded on all the four
considered islets, i.e. Arthrocnemum macrostachyum
and Capparis spinosa subsp. rupestris, are very
common in all the circum-Sicilian islets and stacks
(Pasta, 1997a).

Faunistic notes

The detected remains of Mustela nivalis on
PRE represent the first record of the species for
the whole Egadi Archipelago (Sarà, 1998; Siracusa
& Lo Duca, 2008). Its regular presence on the islet
seems quite improbable, while it might have reached
PRE as a carcass picked up by a seagull or as a
prey of the barn-owl, Tyto alba (Scopoli, 1769), or
the buzzard, Buteo buteo (Linnaeus, 1758), two