The genetic diversity of Bactrocera dorsalis (Diptera: Tephritidae) in China and neighboring countries: A review from published studies

Authors: GARZON-ORDUNA, IVONNE - University Of Hawaii; Geib, Scott; BARR, NORMAN - Animal And Plant Health Inspection Service (APHIS)

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/11/2019
Publication Date: 4/20/2019
Citation: Garzon-Orduna, I.J., Geib, S.M., Barr, N.B. 2019. The genetic diversity of Bactrocera dorsalis (Diptera: Tephritidae) in China and neighboring countries: A review from published studies. Journal of Economic Entomology. 112(4):2001-2006. https://doi.org/10.1093/jee/toz073.
DOI: https://doi.org/10.1093/jee/toz073

Interpretive Summary: The population genetics of the Oriental fruit fly have been extensively studied in China and other countries of South East Asia where the species damages a wide range of the local produce. Primarily based on the mitochondrial fragment COI and on a limited number of flies per locality, these studies have unanimously reported large variation in the COI sequences among and within several populations of the Oriental Fruit fly. Though overall these findings are in agreement with the diversity of other pestiferous fruit flies, it was unclear how generalized the results of these studies were to the entire region. In our short communication we report the results of compiling and comparing the data used in seven population genetics studies published from 2005 to 2017, and discuss the implications of our findings to the overall picture of the genetic diversity of B.dorsalis in China and neighboring countries. We found that despite various studies sampling the same province within China along the years, new haplotypes of the fly are discovered each time and very few, previously sampled haplotypes, are recovered. We hypothesized that if this trend continues, it is likely that many new haplotypes remain to be discovered. Additionally, we report that though studies largely used the same portion of the COI fragment, their sequences differed in length. Thus, our comparisons might underestimate the differences among the sequences and as a result may underestimate the genetic diversity of the fly in this part of Asia. We concluded that the COI diversity contained in populations of the Oriental is not a regional phenomenon and that a large portion of this diversity remains unsampled.

Technical Abstract: For more than a decade, various research groups have tracked the population genetics of the oriental fruit fly, Bactrocera dorsalis (Hendel) in China and neighboring countries using mitochondrial COI DNA. Although study after study has reported high levels of mtDNA variation, to date no efforts have been made to integrate and compare the results from these studies all at once. Here we show that: 1) Despite the fact that a large portion of the sampling effort has focused on the Yunnan province beginning in 2005, each subsequent study recovers only a small number of haplotypes previously sampled; 2) New haplotypes of B.dorsalis remain to be found, a projection of new haplotypes vs. the number of individuals sampled suggest the species mtDNA diversity is far from reaching an asymptote; 3) It is unlikely that the observed genetic variation is the result of NUMTs, as most differences between haplotypes are silent substitutions; and 4) Although all studies employed the 3’ end of COI, the length of COI fragment sequenced differs among studies, making comparisons challenging. Therefore, we offer these results with the caveat that mtDNA diversity might be underestimated in China.