Phylogenetic relationships in the genus Lethrus (Coleoptera: Geotrupidae) reveal contrasting evolutionary history in Europe

In this study we analysed for the first time the phylogenetic relationships among the European Lethrus species based on mitochondrial (COI, 16S) and nuclear (H3, wingless) markers. The phylogenetic inference based on these genes indicated that the European Lethrus species form a monophyletic group with two main lineages. One of them is distributed in the central part of the Balkan Peninsula (North Macedonia, northwestern Greece and southwestern Bulgaria) and includes five species (L. perun, L. raymondi, L. strymonensis, L. halkidikiensis and L. elephas). Three species of the other clade (L. schaumii, L. ares and L. schneideri) occur in the eastern part of the Balkan Peninsula (southeastern Bulgaria and northeastern Greece) while its fourth member, L. apterus, could colonize much larger areas in central and eastern Europe. Despite its large geographic distribution, L. apterus proved to be a single species. By contrast, we found strong intraspecific differentiation in both L. schaumii and L. halkidikiensis in spite of their restricted distribution. Surprisingly, two highly divergent mitogroups were also detected within a single L. schneideri population. As the microsatellite markers did not show any differentiation between them, this finding is likely to be accounted for by a unidirectional hybridization event. These findings highlight that phylogenetic studies or species descriptions should not be based on mitochondrial markers alone. Our study clearly demonstrates that allopatric speciation is the most important speciation mechanism in the European species of the genus Lethrus, although we also hypothesize that other well‐known factors, such as hybridization or the glacial‐interglacial dynamics, could significantly affect the speciation patterns of certain lineages

Limited genetic exchanges between populations of an insect pest living on uncultivated and related cultivated host plants

Habitats in agroecosystems are ephemeral, and are characterized by frequent disturbances forcing pest species to successively colonize various hosts belonging either to the cultivated or to the uncultivated part of the agricultural landscape. The role of wild habitats as reservoirs or refuges for the aphid Sitobion avenae that colonize cultivated fields was assessed by investigating the genetic structure of populations collected on both cereal crops (wheat, barley and oat) and uncultivated hosts (Yorkshire fog, cocksfoot, bulbous oatgrass and tall oatgrass) in western France. Classical genetic analyses and Bayesian clustering algorithms indicate that genetic differentiation is high between populations collected on uncultivated hosts and on crops, revealing a relatively limited gene flow between the uncultivated margins and the cultivated part of the agroecosystem. A closer genetic relatedness was observed between populations living on plants belonging to the same tribe (Triticeae, Poeae and Aveneae tribes) where aphid genotypes appeared not to be specialized on a single host, but rather using a group of related plant species. Causes of this ecological differentiation and its implications for integrated pest management of S. avenae as cereals pest are discussed