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VARIABILITY IN LAND SNAILS 819

subgenera by Hesse (1907). Redescription of this the phylogenetic placement of five new species of Napaeus
taxon will be tackled in a future study. (Gastropoda, Pulmonata, Enidae). Biological Journal of the
Identified clades of the other Sicilian Marmorana Linnean Society 89: 169–187.
were separated by genetic distances from 0.01 to 0.09 Alonso MR, López Alcántara A, Rivas P, Ibáñez M. 1985.
(maximum likelihood distance estimates). Five of the A biogeographic study of Iberus gualterianus (L.) (Pulmo-
six assemblages recognized correspond to geographic nata: Helicidae). Soosiana 13: 1–10.
groups; the sixth (not corresponding to a geographic Alonso MR, Nogales M, Ibáñez M. 2006b. The use of the
computer-assisted measurements utility. Journal of Con-
group) includes specimens of ‘M. muralis’. At this
stage, it is not clear whether Marmorana populations chology 39: 41–48.
Arbogast BS, Kenagy GJ. 2001. Comparative phylogeogra-
should be regarded as a single polytypic species or phy as an integrative approach to historical biogeography.
whether identified assemblages should be regarded as
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semispecies of a superspecies. Avise JC, Arnold J, Ball RM, Bermingham E, Lamb T,
In the light of mating and viable offspring among
Neigl JE, Reeb CA, Saunders NC. 1987. The mitochon-
populations with different shell shape, Sicilian Mar-
drial DNA bridge between population genetics and system-
morana are presumably a Rassenkreis, a polytypic atics. Annual Review of Ecology and Systematics 3: 457–498.
species, as already proposed by Rensch (1937). On the Baminger H, Haase M. 2000. Variation of distal genitalia
other hand, the evidence of genetic differentiation in the simultaneously hermaphroditic land snail Arianta
reported in the present study suggests that the Sicil- arbustorum (Pulmonata, Stylommatophora) caused by
ian Marmorana might be regarded as a superspecies sexual selection? Biological Journal of the Linnean Society
(Mayr, 1963) rather than as a unique polytypic 71: 599–613.
species. Genetic distance per se does not define Bank RA. 2007. Fauna Europaea: Gastropoda, Helicidae.
species and is not the last word on species-level Fauna Europaea version 1.1. Available at http://www.
taxonomy (Davis, 1994); however, if morphology and faunaeur.org (last accessed 8 January 2007).
genetics diverge at different rates, taxa within a clade Baur B, Locher R, Baur A. 1998. Sperm allocation in the
should be calibrated with respect to genetic distance simultaneously hermaphroditic land snail Arianta arbus-
(Davis, 1994; Douris et al., 1998). torum. Animal Behaviour 56: 839–845.
Indeed, further studies are needed to investigate Berbee ML, Carmean DA, Winka K. 2000. Ribosomal DNA
ongoing speciation among the clades found in this and resolution of branching order among the Ascomycota:
group of snails, with special regard to contact zones how many nucleotides are enough? Molecular Phylogenetics
where intermediate shapes are present. Moreover, it and Evolution 17: 337–344.
Cadima JFCL, Jolliffe IT. 1996. Size- and shape-related
will be useful to compare Sicilian Marmorana phy-
logeny with those of the other three closely-related principal component analysis. Biometrics 52: 710–716.
Cain AJ, Cowie RH. 1978. Activity of different species of
genera/subgenera: the Sardinian Tyrrheniberus; the
land-snail on surfaces of different inclinations. Journal of
Sardinian and Corsican Marmorana (s.s.); and the
Conchology 29: 267–272.
Ambigua of the central and southern Apennines.
Carlini DB, Chen Y, Stephan W. 2001. The relationship
between third-codon position nucleotide content, codon bias,
ACKNOWLEDGEMENTS mRNA secondary structure and gene expression in the
drosophilid alcohol dehydrogenase genes Adh and Adhr.
We thank H. Ampt (Siena) for revising the English Genetics 159: 623–633.
and T. Caruso (Siena) for suggestions and help with Chiba S. 1997. Novel colour polymorphisms in a hybrid zone
statistical analysis. T. Wilke (Giessen) provided valu- of Mandarina. Biological Journal of the Linnean Society 61:
able and constructive comments on the manuscript. 369–384.
Research was financed by Siena University (PAR, Chiba S. 1999. Accelerated evolution of land snails Manda-
2005); project ‘I molluschi non marini della fauna rina in the oceanic Bonin Islands: evidence from mitochon-
italiana: filogenesi, sistematica, faunistica, zoogeogra- drial DNA sequences. Evolution 53: 460–471.
fia, conservazione’. Chiu YW, Chen HC, Lee SC, Chen CA. 2002. Morphometric
analysis of shell and operculum variations in the viviparid
snail, Cipangopaludina chinensis (Mollusca: Gastropoda), in
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