Abstract
Meladema Laporte, 1835 are relatively large, stream-dwelling diving beetles, distributed widely in the Western Palaearctic, from the Atlantic Islands to Turkey, and from southern France and the Balkans to the central Sahara. In addition to the three previously recognised taxa (M. coriacea Laporte, 1835, M. imbricata (Wollaston, 1871) and M. lanio (Fabricius, 1775)) we describe a new, cryptic, species from the central Mediterranean area, which can be distinguished from M. coriacea on both DNA sequence data and morphology, and provide a key to known species of the genus. Based on the study of genotyped material, both recent and archival, as well as the examination of a large number of museum specimens, we show that M. lepidoptera sp. n. occurs to the apparent exclusion of M. coriacea on Corsica, Sardinia and islands of the Tuscan Archipelago, but that both taxa are found in peninsular Italy, where they may occasionally hybridize. In the absence of the original type series, we designate a neotype for M. coriacea, and take the opportunity to designate a lectotype for M. lanio. Morphological variation in Meladema species is discussed, including that seen in known and presumed hybrids. Our study highlights the incomplete state of knowledge of Mediterranean biodiversity, even in relatively large, supposedly well-studied taxa.
Highlights
Meladema Laporte, 1835 is a small genus of large diving beetles, found in streams in the Western Palaearctic, from the Canary Islands and Madeira, to western Turkey (Sharp 1882, Guignot 1932, Franciscolo 1979, Balke et al 1989, Balke et al 1990, Ribera et al 2003, Darilmaz and Kiyak 2009, Touaylia et al 2011, Sýkora et al 2017)
Ribera et al (2003) studied the phylogeny and phylogeography of Meladema using mitochondrial DNA sequences, and demonstrated that the genus contains four divergent mtDNA clades, two corresponding to the Atlantic Island species, the other two nesting within M. coriacea; specimens from the island of Corsica being highly divergent from all other material examined from the Canaries, Iberia, the Balearic Islands, southern France and North Africa
Molecular dating analyses suggested that Meladema originated in the Middle Miocene, approximately 14.4 million years ago (MYA; 95% CI 10-20 MYA), with all four extant lineages dating from the early Pleistocene ca. 1.2-1.5 MYA (Sýkora et al 2017)
Summary
Meladema Laporte, 1835 is a small genus of large diving beetles, found in streams in the Western Palaearctic, from the Canary Islands and Madeira, to western Turkey (Sharp 1882, Guignot 1932, Franciscolo 1979, Balke et al 1989, Balke et al 1990, Ribera et al 2003, Darilmaz and Kiyak 2009, Touaylia et al 2011, Sýkora et al 2017). At present the genus contains three species: the widespread Meladema coriacea Laporte, 1835, distributed from the Canary Islands to Turkey and ranging from southern France and the central Balkans south to the central Sahara, and two Atlantic Island endemics, Meladema imbricata (Wollaston, 1871) from the western Canary Islands and Meladema lanio (Fabricius, 1775) from the main island of Madeira. Sýkora et al (2017) surveyed both mitochondrial and nuclear DNA sequence variation across a wider range of localities, confirming the presence of these four genetic lineages, M. coriacea being divided (on both mitochondrial and nuclear markers) into a widespread clade, distributed from the Canary Islands to Turkey, and another clade, restricted in their analyses to Corsica, Sardinia and Montecristo (termed ‘coriacea CSM’). Molecular dating analyses suggested that Meladema originated in the Middle Miocene, approximately 14.4 million years ago (MYA; 95% CI 10-20 MYA), with all four extant lineages dating from the early Pleistocene ca. 1.2-1.5 MYA (Sýkora et al 2017). Ribera et al (2003) and Sýkora et al (2017) refrained from describing ‘coriacea CSM’ as a distinct species, despite its genetic divergence, since it was apparently morphologically identical to other populations of M. coriacea
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