Taxonomy and phylogeny of European Monochamus species: first molecular and karyological data

Abstract

The worldwide distributed genus Monochamus Megerle, 1821 (Coleoptera Cerambicydae) comprises beetles that may become pests of economic importance in conifer stands in the Nearctic and Palearctic Regions. Besides direct damage due to the larval tunnelling habits, they have also been recognized as main vectors of the phytoparasitic nematode Bursaphelenchus xylophilus (Steiner & Buhrer, 1934) (Nematoda Aphelenchoididae). We analysed the complete mitochondrial cytochrome oxidase I gene and a fragment of the small subunit RNA gene sequences (1536 base pairs) in the five European species. These are: Monochamus galloprovincialis (Olivier, 1795), morphologically distinguished in two subspecies M. galloprovincialis galloprovincialis (Olivier, 1795) and M. galloprovincialis pistor (Germar, 1818); Monochamus sutor (Linneus 1758); Monochamus saltuarius (Gebler 1830); Monochamus sartor (Fabricius, 1787) and Monochamus urussovi (Fischer, 1806). For appropriate comparisons, also the Asiatic Monochamus alternatus Hope, 1842 and a Japanese M. saltuarius sample have been analysed. Both genes show an absolute identity between the two subspecies of M. galloprovincialis and a strong affinity between M. sartor and M. urussovi: the morphological subdivisions of the former taxon in two subspecies and of the latter in two entities of specific level are therefore not supported genetically. On the other hand, the Italian and the Japanese samples of M. saltuarius always cluster together in all trees, and for the remaining taxa, no doubt about their rank of specific differentiation emerges from present analyses. From a phyletic point of view, tree topology indicates the Japanese M. alternatus as the most differentiated taxon and the Euroasiatic M. saltuarius as basal to all other strictly European entities. Chromosome analyses show that the diploid autosomal complement ranges from 18 in M. saltuarius to 20 in M. galloprovincialis, and 22 in M. sartor, but a XX-Xy p sex determining system is shared by all analysed taxa. The M. saltuarius karyotype appears as the most primitive from which the others may be derived through Robertsonian fissions. Karyological data therefore agree with molecular analyses in indicating a basal position of Euroasiatic M. saltuarius with respect to the group of European Monochamus taxa; among these, M. galloprovincialis and M. sartor represent two clearly diverging evolutionary units. Furthermore, karyotype analyses substantiate molecular conclusions about the identity between M. galloprovincialis galloprovincialis and M. galloprovincialis pistor.

Evolutionary relationships within EuropeanMonochamus(Coleoptera: Cerambycidae) highlight the role of altitude in species delineation

“…Our molecular data confirm the close relationship of M. galloprovincialis and M. sutor , already considered as sister species in the phylogenetic analyses of the Monochamus by Cesari et al . (). COI mitochondrial gene and 28S nuclear genes allow an accurate delimitation of the two species.…”

“…Three sequences of M. galloprovincialis and one of M. sutor from Italy, published by Cesari et al . () were added to the dataset (GenBank ID: AY260835‐37 and AY260843, respectively). Finally, 76 M. galloprovincialis specimens originating from 35 European and one Moroccan populations, as well as all 50 M. sutor individuals, were used for the intra‐ and interspecific mitochondrial (mt)DNA analysis (Tables ).…”

“…Five species of the genus Monochamus have been described in Europe: Monochamus galloprovincialis (Olivier, 1795), Monochamus sutor (Linnaeus, 1758), Monochamus saltuarius (Gebler, 1830), Monochamus sartor (Fabricius, 1787), and Monochamus urussovi (Fischer, 1806); all attacking conifers and mainly Pinus and Picea species. European Monochamus species are described in the literature as closely‐related species further separated into sub‐species (Cesari et al ., ). Phylogenetic relationships within the European Monochamus remain understudied despite the increased importance of such clarification subsequent to the discovery of the invasive PWN in Portugal (Mota et al ., ; Rodrigues, ; Fonseca et al ., ) and more recently in Spain (Abelleira et al ., ; Robertson et al ., ).…”

“…Although the European species of the genus Monochamus , and mainly M. galloprovincialis , have been subject of numerous studies on their biology and association with PWN (Sousa et al ., ; Naves, Sousa & Quartau, ; Naves, ; Naves et al ., ; Akbulut et al ., ; Koutroumpa et al ., ; Akbulut, ; Akbulut & Stamps, ), literature reports on taxonomy and geographical distribution of Palearctic Monochamus species are scarce (Hellrigl, ; Villiers, ; Tomminen & Leppänen, ; Vives, ; Sama, ). With the exception of one molecular phylogenetic study on the European Monochamus (Cesari et al ., ), the genetic variability at the intra‐ and interspecific level is unknown in Europe.…”

2.4. Cerambycidae Latreille, 1802

“…Karyo logically, cerambycids appear relatively conserva tive. In Ameri can species of the genus Monochamus, several such modifications are known but with constant 2n = 20 chromosomes (Smith & Virkki 1978); in contrast, European species lack modifications but some have 22 or 24 chromosomes (Cesari et al 2005). ek et al 2004).…”