Genetic differentiation of eulophid wasp Quadrastichus erythrinae Kim (Hymenoptera: Eulophidae) from various Erythrina hosts based on mitochondrial and nuclear genes

Many Erythrina trees were found wilting initially and suffering die-back later due to severe infestations by Quadrastichus erythrinae (Hymenoptera: Eulophidae) in Mauritius, Réunion, and Singapore since 2000. It then has widely spread into various countries in tropical and subtropical areas. Various degrees of damage and different symptoms were observed on different host species which raised a question whether the pest belong to same species or not. In order to measure the differentiation of the Erythrina eulophid wasps from different geographic area and host plants, 36 samples from 14 localities of Taiwan and 11 samples from Singapore and Mauritius were collected. Singapore and Mauritius was two of the three countries included in the original description of the new species of Quadrastichus erythrinae Kim. We analyzed mitochondrial genes of 12S ribosomal RNA and cytochrome oxidase I, and nuclear sequence of intergenic spacer 2 to understand their genetic variation and phylogenetic relationship. Sequences of the same region in all the three genes are identical among all the samples. The homogeneity of the genetic composition suggests that there were no cryptic species in the samples. It confirms that all the wasps sampled in this study, despite their different origins in areas and hosts, are belong to the same species. Apparently, all the pests in these countries came from the same monomorphic genotype which quickly and widely spread to other areas.