Abstract
The Asian citrus psyllid Diaphorina citri Kuwayama is a key pest of citrus as the vector of the bacterium causing the “huanglongbing” disease (HLB). To assess the global mtDNA population genetic structure, and possible dispersal history of the pest, we investigated genetic variation at the COI gene collating newly collected samples with all previously published data. Our dataset consists of 356 colonies from 106 geographic sites worldwide. High haplotype diversity (H‐mean = 0.702 ± 0.017), low nucleotide diversity (π‐mean = 0.003), and significant positive selection (Ka/Ks = 32.92) were observed. Forty‐four haplotypes (Hap) were identified, clustered into two matrilines: Both occur in southeastern and southern Asia, North and South America, and Africa; lineages A and B also occur in eastern and western Asia, respectively. The most abundant haplotypes were Hap4 in lineage A (35.67%), and Hap9 in lineage B (41.29%). The haplotype network identified them as the ancestral haplotypes within their respective lineages. Analysis of molecular variance showed significant genetic structure (FST = 0.62, p < .0001) between the lineages, and population genetic analysis suggests geographic structuring. We hypothesize a southern and/or southeastern Asia origin, three dispersal routes, and parallel expansions of two lineages. The hypothesized first route involved the expansion of lineage B from southern Asia into North America via West Asia. The second, the expansion of some lineage A individuals from Southeast Asia into East Asia, and the third involved both lineages from Southeast Asia spreading westward into Africa and subsequently into South America. To test these hypotheses and gain a deeper understanding of the global history of D. citri, more data‐rich approaches will be necessary from the ample toolkit of next‐generation sequencing (NGS). However, this study may serve to guide such sampling and in the development of biological control programs against the global pest D. citri.
Highlights
Genetic structure is the nonrandom distribution of alleles or genotypes in space or time (Mahy, Vekemans, & Jacquemart, 1999)
In recent years, understanding of biological invasion mechanism has increasingly relied on knowledge of the genetic structure of invasive species (Lee, 2002)
To assess the mtDNA population genetic structure, and potential dispersal routes of D. citri, we study global mtDNA genetic differentiation and phylogeography
Summary
Genetic structure is the nonrandom distribution of alleles or genotypes in space or time (Mahy, Vekemans, & Jacquemart, 1999). In recent years, understanding of biological invasion mechanism has increasingly relied on knowledge of the genetic structure of invasive species (Lee, 2002) Such studies can help to illuminate the basic biology and ecology of invasive species, the relationships between the intrinsic genetic characteristics of biological invaders, and their successful invasions (Xu, Zhang, Lu, & Chen, 2001). The available evidence suggests that D. citri originates from the Indian subcontinent (Hollis, 1987) and has subsequently expanded to other subtropical and tropical regions of Asia and to the Indian Ocean islands of Réunion and Mauritius (Waterhouse, 1998), and South America (Halbert & Núñez, 2004) It has reached Central American countries and southern USA (Halbert & Manjunath, 2004). It offers a more holistic insight into D. citri matriline history than have prior studies
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