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Zoomorphology

Table 4 Percentages of correct classification using all shape or only
‘‘size-corrected’’ shape in DFAs, based on the leave-one-out cross-
validation procedure
All shape
Pronotum
PA (%) PB (%)
PA 88.7 11.3
PB 16.3 83.7
PB1 PB2
PB1 80.6 19.4
PB2 23.3 73.7
Elytra
PA PB
PA 100 0
PB 4.9 95.1
PA, Phaleria acuminate; PB, P. bimaculata; PB1, P. bimaculata
‘‘Southern sub-clade’’; PB2, P. bimaculata ‘‘Tyrrhenian sub-clade’’

headland delineated. Such a geomorphology thwarts long-
distance longshore transport of sediment and propagules
between adjacent or close beaches, translating in semi-
isolated macrobenthic assemblages (Deidun et al. 2003;
Deidun and Schembri 2008). However, results from the
present study do not support this hypothesis, since Phaleria
spp. specimens collected from adjacent Maltese pocket
beaches belonged either to different species or to the same
P. bimaculata sub-clade. In order to further test the actual
level of compartmentalization of the studied coastal envi-
ronments, the realization of a broader comparative study
involving diverse molecular markers and taxa with differ-
ent dispersal capacities is thus advisable.
The exploration and definition of character diagnostics
assume a fundamental role in biological conservation; it is
noteworthy to point out that in Australia, the Mediterranean
Fig. 5 Discriminant function analysis between P. acuminata (PA) P. bimaculata has been accidentally introduced in the
and P. bimaculata (PB): a elytra, b pronotum; and discriminant vicinity of Melbourne (Doyen et al. 1989); in such cases,
function analysis between the ‘‘Southern sub-clade’’ (PB1) and the the availability of sound identification methods, as the ones
‘‘Tyrrhenian sub-clade’’ (PB2) within P. bimaculata: c pronotum
described in this paper, is of pivotal importance for an early
recognition of the biological invasions, which otherwise
1997; Millot 1999; Pinardi et al. 2005). The Maltese pop-
might be overlooked and thus inadequately managed.
ulations and the Aegadian ones are thus hydrodynamically
Molecular techniques are known to be extremely effective
linked by virtue of the MAW and of the Atlantic Ionic
in order to unveil these ‘‘cryptic invasions’’ (e.g., Marrone
Stream (AIS) meandering their way through the Sicily Strait
et al. 2011, and references therein), and the geometric
in a southeasterly direction. However, against such a
morphometry proves to be an extremely promising cost-
hydrodynamic regime, gene flow should also be maintained
effective alternative.
between the Aegadian and the Tyrrhenian localities thanks
to the northern stream of the MAW; however, this is
incongruent with results emerging from the current study.
At a finer geographical scale, previous ecological stud-
References
ies on Maltese sandy beaches (e.g., Deidun and Schembri
2008; Gauci et al. 2005) have commented on the pocket Adams DC, Rohlf FJ, Slice D (2004) Geometric morphometrics: ten
nature of the same beaches surveyed, i.e., beaches that are years of progress following the ‘revolution’. Ital J Zool 71:5–16

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