Population genomics of the potato psyllid in the Pacific Northwest

Seasonality of crop production largely influences population dynamics, winter ecology and migration of insects by governing the availability of food source.  The potato psyllid, a small insect species, transmitting a bacterial like disease (“Zebra Chip”), demonstrated seasonal population fluctuations in the Pacific Northwest. Although it was elucidated that potato psyllids feed on bittersweet nightshades, a perennial vine closely related to potatoes off the potato growing season, the genetic variation of psyllids feed on these two host plants has remained elusive. To bridge this knowledge gap, we genotyped 285 of potato psyllids from bittersweet nightshade patches proximal to potato production region of varying seasons and potato fields in season by employing a reduced genome sequencing approach. Psyllids from potato fields exhibited much higher inbreeding coefficient and they were highly admixed and genetically similar to psyllids from surrounding nightshade patches. Indeed, gene flow between psyllid populations can be extended to host plants over 100 km away. However, low genome-wise population differentiation (Fst) of psyllids from two hosts was enriched in Fst differentiation of a group of loci, likely associate to plant host specificity. The psyllid populations demonstrated different temporal patterns and population turnover can occur within a month. In summary, we report an efficient and informative approach to examine temporal and spatial genetic variation of an insect pest species where no available reference genome exists. This information will largely facilitate future investigation of the underlying genetic basis of clinal and phenotypic variation of potato psyllids.