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Biological Journal of the Linnean Society, 2008, 94, 809–823. With 6 figures

Phylogeography and morphological variability in land
snails: the Sicilian Marmorana (Pulmonata, Helicidae)

1
1
2
VIVIANA FIORENTINO *, NICOLA SALOMONE , GIUSEPPE MANGANELLI and
FOLCO GIUSTI 1
1
University of Siena, Dipartimento di Scienze Ambientali, Via P. A. Mattioli 4, 53100 Siena, Italy
2
University of Siena, Dipartimento di Biologia Evolutiva, Via A. Moro 2, 53100 Siena, Italy
Received 12 July 2007; accepted for publication 12 October 2007

Land snails have long been recognized as suitable organisms for studying phenotypic differentiation and phylogeny
in relation to geographical distribution. Morphological data (shell and anatomy biometry on different geographical
scales) and partial sequences from mitochondrial genes (cytochrome oxidase subunit I, 16S rDNA) were used to test
whether morphological patterns match phylogeny in a diversified group of Sicilian rock-dwelling land snails
belonging to the genus Marmorana. The taxonomic implications of the three character sets (shell and anatomical
biometry and molecular data) were also considered. The inferred phylogenetic relationships do not match
morphological (shell and genitalia) patterns. This result may significantly modify the current taxonomy. Mito-
chondrial based reconstructions define several supported clades well correlated with geographic distribution and
populations were found to be distributed parapatrically. The progressive decline in mitochondrial DNA sequence
similarity over a distance of 250 km is consistent with a model of isolation by distance, a pattern previously
recognized for other groups of land snails. For one clade of Marmorana, colonization along Mediterranean trade
routes appears to be a possibility. © 2008 The Linnean Society of London, Biological Journal of the Linnean
Society, 2008, 94, 809–823.
ADDITIONAL KEYWORDS: biometry – gastropods – phenotypic diversity.

INTRODUCTION indistinguishable by shell characters are genetically
differentiated and taxa formerly considered distinct
Land snails are an enlightening groups of inverte-
by shell characters are found to be genetically indis-
brates for understanding evolutionary processes, tinguishable (Giusti & Manganelli, 1992; Alonso,
mainly because of their low vagility and capacity for
Nogales & Ibáñez, 2006b). Moreover, at species level,
dispersion. Land snails are also considered suitable allozymes and DNA data (Johnson & Black, 2000;
subjects for studies in evolutionary biology, due to
Goodacre & Wade, 2001) are often consistent with
their highly polymorphic shell colour and variability anatomical characters, but not with conchological
of shell shape (e.g. European helicids Arianta and
ones. Many hypotheses may be formulated for each
Cepaea: Goodacre, Thomaz & Davies, 2006; Polyne- case (e.g. shell as a consequence of adaptive conver-
sian Partula: Johnson, Murray & Clarke, 1993;
gence, different rates of evolution for each set of
Cuban Polymita: Reyes-Tur, Fernández & Suárez,
characters or different inter- intraspecific rates of
2001; Japanese Mandarina: Chiba, 1997). In addition
variation).
to phenotypic variability, many land snails have high
In the present study, we investigate the Sicilian
genetic diversity (Chiba, 1999; Goodacre & Wade,
helicid rock-dwelling land snail Marmorana as a
2001). As a consequence, conchological, anatomical,
model organism. Among Sicilian rock-dwelling land
and molecular data often do not agree. Taxa almost
snails, Marmorana is one of the most diversified
genera: it has a Tyrrhenian distribution, with species
*Corresponding author. E-mail: vivianafiorentino@unisi.it in Sardinia and Corsica [assigned to Marmorana
© 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 94, 809–823 809
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