Jauharlina, J. | Search bioRxiv

bioRxiv2019

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

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.

evolutionary biology↗

bioRxiv2019

Tritrophic interactions involving a dioecious fig tree, its fig pollinating wasp and fig nematodes

Many species of fig trees (Ficus spp., Moraceae) have nematodes that develop inside their inflorescences (figs). Nematodes are carried into young figs by females of the trees host-specific pollinating fig wasps (Agaonidae) that enter the figs to lay their eggs. The majority of Asian fig trees are functionally dioecious. Pollinators that enter figs on female trees cannot reproduce and offspring of any nematodes they carry will also be trapped inside. The biology of the nematodes is diverse, but poorly understood. We contrasted the development of nematodes carried by the pollinating fig wasp Ceratosolen solmsi marchali into figs on male and female trees of Ficus hispida in Sumatra, Indonesia. Figs were sampled from both male and female trees over a six-month period, with the nematodes extracted to record their development of their populations inside the figs. Populations of three species of nematodes developed routinely inside figs of both sexes: Caenorhabditis sp. (Rhabditidae), Ficophagus cf. centerae and Martininema baculum (both Aphelenchoididae). This is the first record of a Caenorhabditis sp. associated with F. hispida. Mean numbers of nematodes reached around 120-140 in both male and female figs. These peak population sizes coincided with the emergence of the new generation of adult fig wasps in male fig trees. We conclude that figs on female trees can support development and reproduction of some nematode species, but the absence of vectors means that their populations cannot persist beyond the lifetime of a single fig. Just like their fig wasp vectors, the nematodes cannot avoid this routine source of mortality.

ecology↗