Page 4 - CatraEgadi2006

a b

p p
9. 15% 7.89"/o

A A
40.49% 43.23%

lP lP
4.93% 3.38%

CB

c c

23.59% 24.44%

Fig. 2. Comparison of the biogeographic relationships of the present (a) and previous (b) recorded
floras. A = Atlantic (including: boreo-Atlantic; boreo-tropical Atlantic; Atlanto-Pacific; Atlanto-
Pacific tropical; Atlanto-Paci fic cold temperate; Atlantic lropical; Indo-Atlantic; lndo-Atlantic cold
temperate); C = Cosmopolitan (including Subcosmopolitan); CB = Circumboreal (including
Circumboreo-austral); lP= Indo-Pacific; M= Mediterranean; P= Pantropical.

recorded were not found during the present study (Table 3). These figures indicate
significant relative percentage change in both the Rhodophyta and Ochrophyta (with
an increase of 8.61 % and a decreases of 6.51 %, respectively) and a slight percentage
change in the Chlorophyta (with a decrease of 2.09%). From a phytogeographic
point of view, it should be noted that there has been a percentage decrease of Atlantic
(2.74%), Cosmopolitan (0.85%) and Circumboreal (0.92%) elements. Conversely,
there is an increase of Mediterranean (l.70%), lndo-Pacitìc ( 1.55%) and Pantropical
( 1.26%) elements (Fig. 2). O n one hand, both the increase in Rhodophyta and the
decrease in Ochrophyta as well as the increase in both Indo-Pacific and Pantropical
elements is evidence of the process of tropicalization that is impacting the
Mediterranean Sea. On the other hand it should be noted that, unlike what is being
recorded in the eastern Mediterranean basin, there is no recorded deterioration in the
benthic algal vegetation. Along the eastern coast of Sicily, at Pantelleria Island,
Linosa Island and at the Tremiti Islands (Adriatic Sea), the disappearance of
communities associated with Cystoseira spp (a canopy dominant genus on rocky
substrata) has been recorded by Marino et al. ( 1999), Alongi et al. (2004) and Serio
et al. (in prep.), Cormaci et al. (2000, 2001), respectively, but such a phenomenon
has not occurred at the Egadi islands. In these islands, even though some Cystoseira
spp. (like C. crinita, C. dubia , C. elegans, C. sauvageauana) have disappeared, the
communities associated with Cystoseira spp. that there were present in the 1970s are
stili there and are well structured. Therefore, the present study lets to suppose that
the deterioration of the benthic algal vegetation, resulting in the disappearance of
comrnunities associated with Cystoseira spp, is for the moment limited, in ltaly, to

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