Differences in Morphology, Mitochondrial Genomes, and Reproductive Compatibility Between Two Clades of Aphelinus Mali in China

Abstract Aphelinus mali (Haldeman) (Hymenoptera: Aphelinidae) in China is comprised of two clades (Shandong and Liaoning). In order to clarify the genetic relationship of them, we compared and analyzed the morphological characteristics and the mitochondrial genome of each, and ran a hybridization experiment between these clades. Morphological results showed that both males and females of the Liaoning clade were larger than Shandong clade, in terms of whole body, abdominal lengths and antennal lengths, but there were no significant differences between clades for total lengths of the middle and hind foot of females. The arrangement of the mitochondrial genomes was same in both clades, and each contained 31 genes, including 13 protein-encoded genes, 16 tRNA genes, and 2 rRNA genes. The highest AT levels among the 13 protein-coding genes for the two clades were the same gene (atp8) (Shandong clade, 91.52%; Liaoning clade, 90.91%). By hybridization and backcrossing, we found there was no cross incompatibility between these two clades of A. mali. Our results indicate that the historic geographical isolation between these two A. mali clades has not yet caused reproductive isolation of these two geographically separated populations, and they belong to the same species.