Mitochondrial DNA in North American Lygus (Hemiptera: Miridae) species: Analysis of intra- and inter-specific relationships.

摘要

The genus Lygus is widely distributed in North America and Eurasia. Little information is available on the genetic diversity of this group. The present study represents the first attempt to survey genetic variation among Lygus pest species and construct a molecular phylogeny for the genus. The inter- and intraspecific genetic diversity of North American Lygus spp. was investigated by using the mitochondrial genes cytochrome oxidase 1 and cytochrome oxidase 2 (i.e., cox1 and cox2 , respectively). The 658-bp mitochondrial barcode region ( cox1) and a 768-bp (base pair) region overlapping cox1 and cox2 were sequenced. The cox1 and cox2 mitochondrial genes were analyzed in eight Lygus species collected from multiple sites in North America and Europe to determine the monophyly or paraphyly of multiple Lygus species.;The highly polyphagous tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), is the most widely distributed Lygus species in North America. Multiple collections of L. lineolaris from three disparate regions of North America were examined to assess its intraspecific diversity. The 768-bp cox1-cox2 nucleotide sequence codes for two partial amino acid peptides. The cox1 (1-355 bp) and cox2 (417-768 bp) sequences with intervening t-RNA (351-416 bp) are A+T rich (73%). The 768-bp mitochondrial DNA segments have 26 polymorphic nucleotide sites (3.4%), of which seven (0.91%) are phylogenetically informative.;Molecular results show that most L. lineolaris individuals belong to two closely related clades that display sympatric distribution with a geographical frequency bias. A striking incongruence between morphological identity and genetic data of five L. lineolaris samples that formed an outlier clade was also observed. No recognizable morphological differences were exhibited between the individuals from the two major clades and an outlier clade.;Phylogenetic analyses of mitochondrial DNA in the genus show strong support for monophyly of four Lygus species (L. lineolaris , L. plagiatus Uhler, L. rugulipennis Poppius, and L. vanduzeei Knight). However, L. elisus Van Duzee, L. hesperus Knight, L. borealis Kelton, L. keltoni Schwartz and Foottit, and L. solidaginis (Kelton) do not appear to be monophyletic. Further investigation is needed to resolve the discrepancies between morphological and molecular characteristics among these taxa.