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Zoomorphology

Table 3 Molecular distances among the clades and sub-clades sin- Fig. 4 Scatterplots of two first relative warps scores obtained from c
gled out in Fig. 5a the RWM of the shape of two external morphological structures. Plots
show deformation grids relative to each axis; a pronotum:
PA PB1 PB2 Out. RW1 ? RW2 accounted for a total of 79.11 %; b elytra: for a total
of 71.01 %
P. acuminata(PA) 0.06 0.06 0.18
P. bimaculata ‘‘Southern sub-clade’’ 0.07 0.01 0.17 consistent discriminant character among the studied spe-
(PB1)
cies (Fig. 5a, b; Table 4).
P. bimaculata ‘‘Tyrrhenian sub-clade’’ 0.07 0.01 0.17
(PB2) The morphogenetic approach allowed us to further dis-
criminate two well-characterized sub-clades within P. bi-
Out-group (Nesotes helleri) 0.27 0.26 0.26
maculata; these are geographically segregated, and they are
Uncorrected p distances (above the diagonal) and distances based on separated by modest molecular distances (Table 3) and by
the best evolutionary model selected by AIC (GTR ? I, below the
diagonal) the pronotum morphometry (Fig. 4c). One of these groups
includes all the P. bimaculata populations sampled along
the Strait of Sicily, from the Maltese archipelago to the
populations from the island of Vulcano, i.e., VUL_GE and Pelagian and the Aegadian archipelago (the ‘‘Southern sub-
VUL_PV (within the Aeolian archipelago, the locus typi- clade’’), and the other one includes all the populations from
cus of P. bimaculata marcuzzii), did not cluster together in the northeastern Sicilian coast, Vulcano island (Aeolian
the DFA: One of them clustered within the P. acuminata archipelago), and southernmost Italian mainland (the
populations, and the second one clustered within the P. ‘‘Tyrrhenian sub-clade’’) (Fig. 3). This second group thus
bimaculata s.l. populations belonging to the ‘‘Tyrrhenian includes also the P. bimaculata populations currently
sub-clade.’’ ascribed to the subspecies P. bimaculata marcuzzii.
All the pairwise comparisons performed by the DFA At the current state of knowledge, both the mutually
were highly significant (p \ 0.0001) and the relative clas- exclusive hypotheses that (1) P. bimaculata marcuzzii is a
sifications proved to be reliable. The classification table valid subspecies with a wider distribution than previously
(Table 4) shows the percentage correct attributions to the a thought, i.e., extending over the entire Aeolian archipelago
priori molecularly identified groups (i.e., PA: P. acuminata and the southeastern Tyrrhenian coasts, and that (2) P.
vs. PB: P. bimaculata; PB1: P. bimaculata ‘‘Southern sub- bimaculata marcuzzii is in fact a junior synonym of another
clade’’ vs. PB2: P. bimaculata ‘‘Tyrrhenian sub-clade’’). P. bimaculata subspecies, are equally plausible and
deserve further investigation. A future broader sampling
protocol, which includes the topotypical populations of the
Discussion presumptive subspecies and different ‘‘forms’’ of P. bi-
maculata, is needed in order to check whether these alleged
There is a perfect agreement between geometric mor- taxa of infra-specific rank coincide with well-defined
phometry and molecular analyses in assigning the studied molecular lineages.
Phaleria populations to the species P. acuminata or P. Tenebrionid beetles lack a planktonic larval stage;
bimaculata s.l. Previously, a good agreement was observed however, the processes of water transport and rafting
also with the identification results from the conventional (passive dispersal through floating debris) between islands,
morphological investigation, with the only exception being described already for species like the oniscid isopod genus
the population from Vulcano-Gelso (VUL_GE), which was Idotea (ClarkinE et al. 2012), cannot be a priori dismissed
assigned to P. bimaculata marcuzzii by Deidun et al. (Fattorini 2002). Though other species inhabiting sandy
(2011), while it is ascribed to P. acuminate in the present beaches and exhibiting passive dispersal patterns, such as
study on the bases of both morphometric and molecular talitrid amphipods, show a population genetic structure
evidence. Upon a careful morphological reanalysis, in fact, shaped by the surface circulation of water masses (Pavesi
the Vulcano-Gelso population proved to belong to P. bi- et al. 2012), the geographical segregation of the two P.
maculata s.l., thus providing evidence that the original bimaculata sub-clades is not consistent with the prevailing
identification of the same samples as reported by Deidun pattern of surface currents within the central Mediterranean.
et al. (2011) was erroneous. The taxonomical value and the The modified Atlantic water (MAW) stream bifurcates into
species-level discriminatory power of the geometric mor- two major streams just off the westernmost tip of Sicily
phometrics analyses in Tenebrionidae, already demon- (Fig. 3b), with one stream meandering along the northern
strated for different genera (e.g., Taravati et al. 2009; Peric- coast of Sicily, in the southern Tyrrhenian, and one stream
Mataruga et al. 2008), are thus also confirmed for the genus proceeding in a southeastern fashion, just south of Adven-
Phaleria, where the elytra and the pronotum proved to be ture Bank, in the Strait of Sicily (Malanotte-Rizzoli et al.

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