Whole genome sequencing of 358 brown planthoppers uncovers the landscape of their migration and dispersal worldwide

Abstract

The brown planthopper (BPH), Nilaparvata lugens, is a serious migratory rice pest, which is distributed in the broad area of the tropical and temperate Asian-Pacific region. However, we know little about key aspects regarding its evolution such as how they diverged and dispersed worldwide. By resequencing and analyzing 358 BPH genomes from 92 populations across the world, we uncover the genetic relationships among their worldwide populations and the history of their global dispersal. We recovered five genetic groups representing the major population structures. Of these, Australian BPHs were shown large genetic divergence with Asian BPHs; two distinct groups have formed in South and Southeast/East Asia that show strong genetic admixture in the southwest border regions of China and west Thailand with Myanmar; two local populations in Bangladesh and Fujian province of China, respectively, unexpectedly separated with surrounding populations. We also find the genetic similarity and closely phylogenetic relationships between majority of East Asian BPHs and Indo-china peninsula BPHs, indicating that Southeast Asia mainland is the major insect sources and overwintering sites for East Asia.Our study provides important molecular evidence to address BPH evolution and other key aspects of its biology such as insecticides resistance and rice varieties virulence.

Plagues of Desert Locusts: Very Low Invasion Risk to China

“…Moreover, the fall armyworm in Myanmar was first detected on maize plants in the Mandalay and Ayeyawaddy Regions in late 2018 or early 2019, and these regions are on, or close to, the coast [ 25 ], thus reinforcing the view that fall armyworm migrate into Myanmar from India by crossing the Bay of Bengal. Recent studies have reported that there are frequent genetic exchanges in migratory insects between southern India and southern China, such as the brown planthopper ( Nilaparvata lugens ) [ 26 ] and tobacco cutworm ( Spodoptera litura ) [ 27 ], and this also suggests that insects can migrate from southern India into southern China. It should be emphasized that southern India is suitable for these insect species.…”

The ‘migratory connectivity’ concept, and its applicability to insect migrants

“…This supposition is supported by phenotypic differences between brown planthopper from the two regions, such as distinct virulence levels against resistant rice strains [80]. A recent analysis indicates that the South East / East Asian and South Asian clades are somewhat genetically divergent, but that there is a greater degree of gene flow between the two groups than was previously suspected [79]. In particular, brown planthopper from Myanmar, Yunnan (southwest China), Thailand and Laos showed a high degree of ancestry from South Asia, but all samples from the South East / East Asian range had experienced some gene flow from South Asian populations [79].…”

“…Further entomological radar [87], genetic [40,41,63,79], stable isotope [11,15,28,42] and individual marking [35,88] studies carried out in other regions and biomes of the world are needed to answer questions about the level of connectivity in insect migration systems. An exciting recent development is the reduction in weight of electronic tagging devices [89] which may help to get better flightpath data for very large insects (such as green darner dragonflies [65,67]), although it will take time to build up a database of migratory tracks (such as those emerging from decades of bird tagging).…”

“…A recent analysis indicates that the South East / East Asian and South Asian clades are somewhat genetically divergent, but that there is a greater degree of gene flow between the two groups than was previously suspected [79]. In particular, brown planthopper from Myanmar, Yunnan (southwest China), Thailand and Laos showed a high degree of ancestry from South Asia, but all samples from the South East / East Asian range had experienced some gene flow from South Asian populations [79]. These findings indicate that there must be frequent mixing between the South Asian and South East Asian populations, resulting in a relatively low level of migratory connectivity within these two geographic populations (Fig.…”

“…In late summer and autumn, return migrations by later generations of brown planthopper are promoted by persistent north-easterly winds associated with the winter monsoon [71,78]. This migratory loop between South East and East Asia is entirely regulated by the movement of the monsoon and associated winds [16], and it is generally assumed that this South East / East Asian migratory population is genetically distinct from the South Asian population [79]. This supposition is supported by phenotypic differences between brown planthopper from the two regions, such as distinct virulence levels against resistant rice strains [80].…”