Strigamia acuminata (Leach, 1816)

Bonato, Lucio, Bortolin, Francesca, Zen, Giada De, Decker, Peter, Lindner, E. Norman, Orlando, Marco, Spelda, Jörg & Wesener, Karin Voigtländer and Thomas, 2023, Towards elucidating species diversity of European inland Strigamia (Chilopoda: Geophilomorpha): a first reassessment integrating multiple lines of evidence, Zoological Journal of the Linnean Society 199 (4), pp. 945-966 : 955-957

Strigamia acuminata (Leach, 1816) species complex

Diagnosis of adult individuals: Usually ≤ 2–3 cm long; clypeal setae arranged in three groups, i.e. with distinct gaps between intermediate and lateral groups of setae; forcipular tergite usually 30–40% of the head length; forcipules relatively slender and relatively separated from each other (distance between the basal condyles> 1.6 times the basal width of the forcipules); forcipular tibia usually without a distinct projection, at most a very small tubercle or a shallow bump; tarsungulum elongate (on average 80% of the distance between the basal forcipular condyles, rarely <70%), with the outlines of the intermediate part (i.e, basal part of the ungulum) either distinctly converging or sub-parallel; forcipular denticle relatively short (usually 40–50% of the tarsungulum length) and its outlines usually straight; 39–43 leg pairs, almost invariantly 41 in females and 39 in males; metasternites of the anterior one-third of the trunk without a mid-longitudinal sclerotized stripe, only a shallow groove; each coxopleuron with relatively few coxal pores in proportion to body size, i.e. usually no more than 15 pores in individuals ≤ 25 mm long and no more than 25 pores in longer individuals; coxal pores relatively small in proportion to body size, diameter of the largest pore usually <4% of the head width and usually distinctly narrower than their canals.

Geographical distribution: Within the study area, species of the S. acuminata complex are widespread from the northern coastal plain, through the Alps to the Apennines and southwards to the Nebrodi mountains in Sicily ( Fig. 6 ). They are apparently missing from Corsica and Sardinia.

Outside the study area, species of the S. acuminata complex inhabit a broad part of Europe: westwards to the Pyrenees ( Barace and Herrera 1980), Briưany ( Iorio 2014) and Great Britain ( Barber 2022); northwards to the southern part of the Jutland Peninsula ( Lohmander 1957, Andersson et al. 2008); eastwards to the Volga basin and Caucasus (summarized by Bonato et al. 2012); and southwards to Anatolia ( Zapparoli 1999) and southern Dinarides ( Kaczmarek 1969, Stoev 2002), but also Crete ( Simaiakis et al. 2004). Other published records from other areas have been questioned (e.g. Bonato et al. 2012) or need confirmation.

Candidate species: Different lines of evidence suggest at least two species. A candidate species ( Fig. 4 B’) seems to differ from the other species in the shape of the forcipules: the tarsungula are much more elongate than in the other species (usually> 85% of the distance between the basal forcipular condyles, on average 88%, vs. usually <85%, on average 78%; Mann–Whitney U -test: U = 371, z = −4.26, P <.00001, N = 28 vs. 46; Supporting Information, Fig. S2 ); the outlines of the intermediate part of each tarsungulum are oħen sub-parallel, whereas they are uniformly converging in the other species, and the denticles are relatively shorter than in the other species (usually <45% of the tarsungulum length, on average 43%, vs. usually> 45%, on average 49%; Mann–Whitney U -test: U = 10, z = 6.94, P <.00001, N = 27 vs. 45; Supporting Information, Fig. S2 ). Reliable records of this candidate species are distributed along the south-eastern part of the Alps, from the Bergamasque Prealps to at least the Julian Alps and Prealps ( Fig. 6 ). It is largely parapatric with respect to other candidate species in the same complex, and evidence for their syntopic occurrence is weak. The valid name of this candidate species should be Strigamia microdon (see Supporting Information, Appendix).

Figures

Figure 2. Study area (elevation in grey shades) and sampling sites of the specimens examined for within-population variation (code leưers are as in Supporting Information, Table S2), of the specimens used in the species delimitation analyses by morphological and molecular differentiation (code numbers are as in Supporting Information, Table S3), of all other specimens examined for morphology, and all other published records.

Figure 4. Hypotheses of species delimitation of Strigamiaobtained from different lines of evidence and different methods, illustrated upon the ultrametric tree of the COI. Bootstrap values are indicated whenever different from 100%. Tree tips represent haplotypes, coded as in the Supporting Information (Table S3). Both the previous species identification of the specimens and the revised names of the species complexes are indicated. Intraspecific genetic distances are given in the Supporting Information (Table S6).

Figure 6. Geographical distribution of the Strigamia acuminata species complex and candidate species within the study area, based on direct examination of specimens and critically revised published records.