Page 5 - Pardi&al_2006

Pardi, Piazzi, Balata, Papi, Cinelli & Benedetti-Cecchi Posidonia oceanica epiphytes of Sicily

Table 2. Analysis of variance on mean percentage cover of epiphytes of Posidonia oceanica in Sicily.

encrusting red encrusting brown filamentous encrusting erect
algae bryozoans bryozoans
algae algae hydroids Foraminifera

source of variation d.f. MS F MS F MS F MS F MS F MS F MS F

geographic area (¼A) 2 341,948 4.2 131,826 5.4* 772.9 22.6*** 23,973 4.9* 65.8 0.8 66.5 3.2 7614 8.8**

habitat (¼H) 1 107,398 1.3 64,057 2.6 0.9 0.0 8792 1.8 68.2 0.8 69.9 3.4 3242 3.8

A·H 2 130,715 1.6 15,969 0.7 50.5 0.3 12,977 2.7 65.2 0.8 119.2 5.8* 1692 2.0

meadow (A · H) (¼M) 12 80,658 27.3*** 24,330 15.9*** 34.2 6.0*** 4857 17.2*** 86.4 22.3*** 20.6 6.4*** 865 14.6***

site (M) (¼S) 72 2957 2.7*** 1533 2.7*** 5.7 2.8*** 282 2.3*** 3.9 2.6*** 3.2 2.5*** 59 2.1***

plot (S) (¼P) 370 1088 5.5*** 563 2.2*** 2.0 2.8*** 120 2.0*** 1.5 2.4*** 1.3 2.4*** 28 2.3***

residuals 4050 200 252 0.7 59 0.6 0.5 12

total 4499

Cochrane’s test (C) 0.011 0.014 0.011 0.019 0.010 0.015 0.020

transformation None None ln(x + 1) None ln(x + 1) ln(x + 1) None

SNK test W>N¼S W>N¼S N¼W¼S M: N ¼W¼ S W > N ¼ S

I: S > N ¼ W

N: I ¼ M

W: I ¼ M

S: I > M

*P < 0.05; **P < 0.01; ***P < 0.001.
N ¼ north; W ¼ west; S ¼ south; M ¼ Mainland; I ¼ Island.

Table 3. Variance components analyses conducted on untransformed data and expressed as percentage.

variance encrusting encrusting filamentous encrusting erect hydroids Foraminifera
components red algae brown algae algae bryozoans bryozoans
7.57 18.08
meadow 48.81 23.16 6.56 21.06 19.77 5.36 3.39
site 5.87 4.93 6.27 3.68 4.22 12.62 9.04
plot 7.90 20.75 7.02 74.45
leaf 13.95 66.40 12.67 69.49
31.36 64.01 68.24 63.34

scale of observation has important implications, from the islands and continental coasts. In the present paper, we
identification of the mechanisms that generate and main- compared leaf epiphytes of Posidonia oceanica meadows
tain biological diversity (Underwood & Chapman 1996; between the two habitats represented by islands and
Willis & Whittaker 2002), to the prediction of how local locations on the mainland coasts in different geograph-
and regional environmental changes will affect diversity at ical areas around Sicily. This was performed by means
multiple levels of organization (Lockwood & McKinney of a multifactorial sampling design that enabled the
2001; Scott et al. 2002), to the analysis of relationships quantitative assessment of variability at a hierarchy of
between species richness and ecological function (Waide spatial scales, ranging from 10s of centimetres to 100s
et al. 1999). The study of spatial patterns of biodiversity of kilometres. Significant differences were detected
in benthic organisms has received considerable attention, among geographic areas for encrusting brown algae, fil-
and a synthesis of these studies suggests that small-scale amentous algae, encrusting bryozoans and Foraminifera.
processes are at least as important as large-scale processes A significant geographic area · habitat interaction was
in many assemblages (Fraschetti et al. 2005). Our results detected only for hydroids, while spatial variability
show that this also applies to ESL, a system common to within each habitat was large and significant, partic-
many marine coastal areas. ularly among shoots 10s of centimetres apart and
meadows a few kilometres apart.
Conclusions
Acknowledgements
Although a number of studies have investigated epi-
phytes on the leaves of seagrasses at different spatial We dedicate the paper to Lucia Mazzella for her contri-
and/or temporal scales, few have focused on geograph- bution to the knowledge of Posidonia oceanica ecosystem,
ical patterns and on differences between the small and in particular to epiphytes. This research was supported

Marine Ecology 27 (2006) 397–403 ª 2006 The Authors. Journal compilation ª 2006 Blackwell Publishing Ltd 401