Is Acerentomon italicum Nosek, 1969 (Protura: Acerentomidae) a species complex?

Abstract: Acerentomon italicum Nosek, 1969 is the most abundant Protura species in Italy. Two groups of populations characterized by the different position of a pore on tergite VII were analyzed. Specimens from Austria and from the Italian provinces of Brescia and Bolzano (Lombardy and Alto Adige, respectively) possess a postero-sub-medial pore (psm); in specimens from Trento (Trentino), Veneto, Friuli-Venezia Giulia and Liguria the pore is in an antero-sub-lateral (asl) position. An integrative approach was applied to assess other characters distinguishing these populations. The lengths of body, head, foretarsus, claw of anterior leg, foretarsal sensilla a and b were measured; in addition some ratios were calculated: TR (length of foretarsus/length of its claw), BS (distance of sensillum t1 from base of foretarsus/distance of t1 from foretarsus tip), length of a/foretarsus length, length of b/foretarsus length and length of a/length of b. A geometric morphometric analysis was performed on the position of setae on tergite VII, selecting as landmarks the bases of setae A1, A2, A3, P1, P1a, P2, P2a and P3. Nucleotide sequences COI-5P and 28S-D2-D3 of both groups were compared. Significant differences in the foretarsus and anterior claw length, in the arrangement of setae on tergite VII and in the barcode sequences COI-5P between the “psm and asl populations” are shown to exist. Based on the results obtained, the two groups are different, but there is not enough support to differentiate them at the species level.