When morphological identification meets genetic data: the case of Lucanus cervus and L. tetraodon (Coleoptera, Lucanidae)

Abstract

The European stag beetle Lucanus cervus, widely distributed across Europe and in some Near East countries, is one of the best known coleopteran\ud species listed in the European Habitats Directive 92/43/EEC and it is considered a flagship species for conservation of saproxylic fauna. Lucanus tetraodon\ud is a closely related species whose geographical distribution is still poorly known and debated. The two species have a sympatric occurrence in\ud central Italy, and in some localities of these areas, many individuals show a mosaic of morphological traits that makes species assignment nearly\ud impossible. We used both mitochondrial and nuclear markers to analyse these specimens. The mitochondrial results evidenced that the two species represent\ud well-defined genetic entities with mitochondrial DNA introgression. This pattern could be the result of either hybridization or of a convergence\ud of morphological characters under local selective pressures in areas of sympatric occurrence. The nuclear marker was polymorphic across the two\ud species and therefore did not reveal hybridization, even if many are the supports to this phenomenon. The most plausible explanation for this genetic\ud pattern is a very recent divergence of the two species which share a common origin and thus a common wg genotype

Guidelines for the monitoring of Lucanus cervus

“…The antennal club is usually made up of the last 5 or 6 (rarely 7) antennomeres, gradually enlarged, when compared to the last antennomere just before the club. As discussed above, these characters are not always diagnostic (see Figure 6) in central Italy where L. cervus and L. tetraodon frequently overlap and probably exhibit phenomena of past hybridisation (Solano et al 2016). This phenomenon occurs mostly in areas between the provinces of Viterbo and Rome in Latium, as well as between the provinces of Perugia and Terni in Umbria.…”

“…In addition, the shape of the male genitalia is not very useful for distinguishing the two species, although they always appear markedly separated by molecular analyses, even when apparently "intermediate" sympatric forms are analysed. In fact, most "intermediate" specimens from central Italy univocally resulted in being L. cervus from a molecular point of view (Solano et al 2016;Figure 6).…”

“…Further molecular analyses are certainly needed on these eastern populations to better understand their actual taxonomic position. As for taxonomic problems involving the correct identification of certain populations of L. cervus and L. tetraodon from Central Italy, refer to Solano et al (2016), and to the discussion in the paragraph "Identification and comparison with similar taxa". In fact, L. tetraodon replaces L. cervus in southern Italy, Corsica and Sicily (Miksic 1959a, 1959b, 1961, Franciscolo 1997, Lapiana and Sparacio 2006, Santoro et al 2009) but there is a well-documented area of overlapping in central Italy, where the two species often live in syntopy (Bartolozzi 1986, Bartolozzi and Maggini 2007, Cortellessa et al 2014, Solano et al 2016) and many specimens (purported to be hybrid) exhibit intermediate morphological characters between the two species (Santoro et al 2009).…”

“…As for taxonomic problems involving the correct identification of certain populations of L. cervus and L. tetraodon from Central Italy, refer to Solano et al (2016), and to the discussion in the paragraph "Identification and comparison with similar taxa". In fact, L. tetraodon replaces L. cervus in southern Italy, Corsica and Sicily (Miksic 1959a, 1959b, 1961, Franciscolo 1997, Lapiana and Sparacio 2006, Santoro et al 2009) but there is a well-documented area of overlapping in central Italy, where the two species often live in syntopy (Bartolozzi 1986, Bartolozzi and Maggini 2007, Cortellessa et al 2014, Solano et al 2016) and many specimens (purported to be hybrid) exhibit intermediate morphological characters between the two species (Santoro et al 2009). In the last dozen years, some records of L. tetraodon in Emilia-Romagna (Fabbri 2010), Liguria (Bartolozzi and Maggini 2007) and Lombardy (Zilioli and Pittino 2004) have extended the Italian distribution range northwards, while in Sardinia, the species has not been found recently (Carpaneto et al 2011b).…”

Evidence for geographic substructuring of mtDNA variation in the East European Hermit beetle (Osmoderma barnabita)

“…Analyses of DNA polymorphisms offer high resolution and can resolve intraspecific patterning even within morphologically similar cryptic species (Hebert et al 2003b, Bickford et al 2007, Murray et al 2008, Huemer and Hebert 2011, Jusoh et al 2014, Solano et al 2016. For efficient species conservation, resolving such patterns is necessary to recognise genetic issues amongst sub-populations, e.g.…”