ARS | Publication request: Two separate introductions of Asian citrus psyllid populations found in the American continents

Submitted to: Annals of the Entomological Society of America
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 3, 2011
Publication Date: November 1, 2011
Citation: De Leon, J.H., Setamou, M., Gastaminza, G., Buenahora, J., Caceres, S., Yamamoto, P., Bouvet, J.P., Logarzo, G. 2011. Two separate introductions of Asian citrus psyllid populations found in the American continents. Annals of the Entomological Society of America. 104(6):1392-1398.

Interpretive Summary: A population genetic study of the Asian citrus psyllid (Diaphorina citri) from the American continent was undertaken in order to determine whether D. citri invaded North America via South America. We also asked whether more than one founding event occurred in the Americas. We asked this question because D. citri has been in South America (Brazil) for the last 70 years. A molecular approach was implemented by sequencing the mitochondrial cytochrome oxidase subunit I gene (COI) from D. citri populations collected in North and South America. A population from Hawaii was also included. The population genetic analysis demonstrated that two founding events occurred in the Americas, one in North America and one in South America. The data suggests that D. citri did not invade North America via South America, rather, each sub-continent was probably invaded by a separate Asian country. The data also suggests that Hawaii and North America also share a similar source of invasion. The practical use of this information is that the source for the collection of natural enemies for D. citri for a biological control program may be different for each sub-continent. The rationale now is to analyze world-wide populations of D. citri to pin-point the origin in order to collect co-evolved or pre-adapted natural enemies per sub-continent.

Technical Abstract: A phylogeographic analysis inferred from the partial mitochondrial cytochrome oxidase subunit I gene (433 bp) was performed with 22 populations (n=132) of Diaphorina citri collected in the Americas and one in the Pacific. Eight populations (n=46) from four countries in South America, 14 (n=76) from four countries in North America, and one from Hawaii (n=10) were analyzed. Twenty-three haplotypes were identified that fell into two groups, hp1-8 were identified in South America (Group 1) and hp9-23 were identified in North America and Hawaii (Group 2). Haplotypes 1 and 9 were present in the highest frequencies within each population and within their group, 81-85%. Sharing of haplotypes was not observed between the two groups. An analysis of molecular variance uncovered significant genetic structure (FCT=0.733; P<0.001) between the two groups in the Americas. A neighbor-joining phylogram and two haplotype networks (ParsimonySplits and Statistical Parsimony) discriminated the two groups, while both networks identified hp1 and 9 as the ancestral or founding haplotypes within their respective group. Significantly negative neutrality tests (Tajima’s D and Fu’s Fs), non-significant mismatch distribution parameters (SSD and HRI), and low genetic diversity levels provided evidence of demographic expansion within each group in the Americas. The data suggest that two founding events of D. citri occurred in the Americas, one in South America and one in North America. Furthermore, North America and Hawaii appear to share a similar source of invasion. These data are important to the development of biological control programs against D. citri.