Meligethes subaeneus Sturm, 1845

Audisio, Paolo, Mancini, Emiliano & Biase, Alessio De, 2006, A new species of the pollen­beetle genus Meligethes (Coleoptera: Nitidulidae) of the M. aeneus group from Greece, with review of the M. subaeneus complex, Zootaxa 1275, pp. 43-60 : 49-50

Meligethes subaeneus Sturm, 1845

( Figs. 2–3 , 7–8 , 14 )

Diagnosis

Small to medium­sized (length 1.70–2.80 mm), variable species, usually dark brown with pale brown to blackish­brown legs and antennae, with maximum pronotal width at posterior angles ( Figs. 2–3 ). Similar to M. epeirosi n.sp. and M. matronalis but with dorsal punctures usually sparser (spaces between punctures 1.3–2.0X diameter), pronotum and elytra much duller and body on average smaller than M. matronalis , and median lobe of the aedeagus distinctive, being much shorter than in M. epeirosi n.sp. and M. matronalis ( Fig. 8 ; ratio LEAE/WIAE [ Fig. 17 f] = 1.66–1.78) and subparallel at sides (in M. epeirosi n.sp. median lobe with maximum width at distal three­fifths, distinctly narrowed both distad and proximad: Figs. 11–12 ). The form of the pronotum and the peculiarly short median lobe of the aedeagus separate M. subaeneus from all other members of the M. coracinus subgroup. Female ovipositor as figured ( Fig. 14 ), apex never darkened.

Geographic distribution

This species is widespread in Europe from NW Spain (Cantabrian Mts.) westward, throughout most of Europe, south to northern Greece and southern peninsular Italy, reaching the northern Caucasus eastward ( Audisio, 1993; Audisio et al., 2000). Overall, it is rare, being locally abundant in certain localities in central and southern Europe (e.g., Pyrenean Mts, Italian Prealpine Range, northern and central Apennines, Transylvanian Alps).

Biological notes

This species shows a clear and geographically­dependent heterogeneity in its relationships with the larval host­plants. Most of the populations from central­southern and southern Europe seem to be associated with Cardamine spp. ( Brassicaceae Arabideae ), especially C. bulbifera L. and several species of the subgenus Dentaria , almost exclusively flowering in Spring (flowers persisting for a couple of weeks from late March to early June, depending on altitude and latitude) in shady forest habitats, such as woods of beech, mesophilous oak, and other meso­hygrophilous broad­leaved tree dominated forests. However, most populations from central, eastern and northern Europe seem to be associated with Cardaminopsis spp. ( Brassicaceae Arabideae ), especially C. arenosa (L.) Hayek and C. halleri (L.) Hayek, which almost exclusively flower in middle Spring (flowers persisting for a couple of weeks from late April to middle June, depending on altitude and latitude) at the edges of shady forest habitats with humid screes and rocky slopes, especially on calcareous soils. Finally, populations from Cantabrian Mts. (NE Spain) are associated with the unrelated Sisymbrium irio L. ( Brassicaceae Sisymbrieae ), flowering in middle Spring (middle May to middle June, depending on altitude, mainly between 400 and 1200 m) at the edges of fragmented forest habitats with shady screes and rocky or terrigenous slopes. We recently demonstrated this latter association by scoring genetic identity based on the comparison of the almost complete COI gene sequences (unpublished data) of larvae and adults from the host plant in Campollo (Comunidad Autonoma de Cantabria, 27.V.2005, E. Mancini leg.).

In certain areas of southern Europe (e.g., NE Italy in Friuli, SW Austria, and central Romania) nearly sympatric populations associated with Cardamine spp. or Cardaminopsis spp. are only separated by a few kilometres.

Taxonomic observations

As discussed by Audisio et al. (2005a), the Cantabrian populations show a moderate degree of morphological and chromatic differentiation. Specimens from these populations are, in fact, characterised by dorsal punctures relatively coarser and deeper, blackish legs and antennae (usually pale brown to brown in typical M. subaeneus ), and shorter elytra (ratio LELY/WELY [ Fig. 17 a] = 0.99–1.05; ratio LEPR/LELY [ Fig. 17 a] = 0.55–0.61; Fig. 3 ), if compared with typical populations of M. subaeneus (ratio LELY/WELY = 1.05–1.09; ratio LEPR/LELY [ Fig. 17 a] =0.45–0.55; Fig. 2 ). This evidence, combined with an association to a larval host plant ( Sisymbrium irio ) distantly related to members of Arabideae ( Cardamine and Cardaminopsis ) used by this species for larval development, suggested that Cantabrian populations could represent a new taxon different from the widespread European M. subaeneus . However, no evidence of strong morphological differentiation was observed among the Cardamine ­ or Cardaminopsis­ associated European populations, albeit the specimens of Cardaminopsis­ associated populations exhibit a relatively smaller and narrower pronotum (ratio WPR1/WELY [ Fig. 17 a] = 0.85–0.90) in comparison with specimens of Cardamine­ associated populations (ratio WPR1/WELY [ Fig. 17 a] = 0.89–0.92; Fig. 2 ). Probably as a consequence of the Pleistocenic glaciation cycles, which isolated populations of the ancestral M. subaeneus in different southern European refugia (Iberian, Italian, and Balkan areas; Hewitt, 1999), the Cantabrian and the European groups of populations, that exhibit (as discussed above) a marked ecological differentiation in their host­plant needs, have made important steps towards their specific differentiation, and should be considered host­races (as interpreted by Drès & Mallet, 2002) or even distinct species.

Figures

FIGURE 17. Schematic drawings of morphological characters measurements for Meligethes species—a: body shape and pronotum; b: antennae; c: protibiae; d: protarsi; e: tegmen; f: aedeagus; g: aedeagal apex. Refer to Table 2 for list of characters and acronyms.

FIGURES 1 – 4. Dorsal habitus of Meligethes epeirosi n. sp. (♂ paratype from Greece, Katara Pass, Fig. 1), of M. subaeneus Sturm (♂ specimen from Italy, Latium, Rocca di Papa, Fig. 2; ♂ specimen from Spain, Cantabria, Campollo, Fig. 3), and of M. matronalis Audisio & Spornraft (♂ specimen from Italy, Latium, Rocca di Papa, Fig. 4). Scale bar = 2.00 mm.

FIGURES 5 – 12. Tegmen and median lobe of aedeagus (dorsal view) of Meligethes coracinus Sturm (♂ specimen from Italy, Lombardia, Lovero Valtellino, Figs. 5 – 6), of M. subaeneus Sturm (♂ specimen from Italy, Latium, Rocca di Papa, Figs. 7 – 8), of M. matronalis Audisio & Spornraft (♂ specimen from Italy, Latium, Rocca di Papa, Figs. 9 – 10) and of Meligethes epeirosi n. sp. (♂ paratype from Greece, Katara Pass, Figs. 11 – 12). Scale bar = 0.50 mm.

FIGURES 13 – 16. Ovipositor of Meligethes coracinus Sturm (Ψ specimen from Italy, Lombardia, San Giacomo di Teglio, Fig. 13), of M. subaeneus Sturm (Ψ specimen from Italy, Latium, Rocca di Papa, Fig. 14), of M. matronalis Audisio & Spornraft (Ψ specimen from Italy, Latium, Rocca di Papa, Fig. 15) and of Meligethes epeirosi n. sp. (Ψ specimen from Greece, Katara Pass, Fig. 16). Scale bar = 0.50 mm.