Species identification of the psammophilous tenebrionid beetles Phaleria acuminata Kuster, 1852 and Phaleria bimaculata (Linnaeus, 1767) from Central Mediterranean beaches : geometric morphometrics and molecular insights from species to population level

Abstract

Dominating global arid environments, from desert to coastal dunes, most Tenebrionidae are highly specific in their habitat preferences and display limited dispersal potential, thus exhibiting a remarkable degree of regional genetic and morphological differentiation. The

tenebrionid genus Phaleria is speciose and widely distributed, with P. acuminata and P. bimaculata having a

wide Mediterranean distribution, with numerous morphological differentiations at population level, often described

as different taxa of doubtful taxonomical significance. In

order to investigate the variability of the central Mediterranean populations of P. bimaculata and P. acuminata and

to compare the results obtained with different identification techniques, these species were sampled on sandy beaches

in Sicily (southern Italy) and on circum-Sicilian and Maltese islands. Collected samples were studied through the

application of geometric morphometrics and the sequencing of a fragment of the mitochondrial COII gene. Geometric morphometrics and molecular analyses gave

congruent results, allowing a sound separation of the two species. At the population level, the two species showed different patterns. P. acuminata showed a remarkable morphological and molecular homogeneity throughout the

sampled area. Conversely, two well-characterized subclades were detected within P. bimaculata, and within the

two lineages, a low-to-absent inter-populations differentiation was observed, in spite of the physical isolation of the

sampled sandy beaches and of their geographical distance.

These two P. bimaculata lineages, hereby named ‘‘Tyrrhenian sub-clade’’ and ‘‘Southern sub-clade,’’ might be

compatible with the hypothesis of subspecific status already proposed for the populations from the Aeolian archipelago (as P. bimaculata marcuzzii Aliquo`).