25 26 Running title: E. corollae genetic structure 27 2 28 Abstract: The hoverfly, Eupeodes corollae, is a worldwide natural enemy of aphids and a 29 plant pollinator. To provide insights into the biology of this species, we examined its 30 population genetic structure by obtaining 1.15-GB random genomic sequences using next-31 generation sequencing and developing genome-wide microsatellite markers. A total of 32 79,138 microsatellite loci were initially isolated from the genomic sequences; after strict 33 selection and further testing of 40 primer pairs in eight individuals, 24 polymorphic 34 microsatellites with high amplification rates were developed. These microsatellites were 35 used to examine the population genetic structure of 96 individuals from four field 36 populations collected across southern to northern China. The number of alleles per locus 37 ranged from 5 to 13 with an average of 8.75; the observed and expected heterozygosity 38 varied from 0.235 to 0.768 and from 0.333 to 0.785, respectively. Population genetic 39 structure analysis showed weak genetic differentiation among the four geographical 40 populations of E. corollae, suggesting a high rate of gene flow reflecting likely widespread 41 migration of E. corollae in China. 42 43 3 46 Introduction 47 Eupeodes corollae is one of the most common hoverflies with a worldwide distribution [1, 2]. 48 The larval stage of this species is mostly insectivorous, feeding mainly on aphids [3-5] while 49 adults are pollinators [6][7][8]. Many hoverfly species are important biological control agents of 50 aphids due to their rapid dispersal and absence of summer diapause compared with other 51 aphidophaga [9]. Understanding the biology and behavior of hoverflies can help in assessing 52 their potential as biological control agents of aphids. 53Hoverflies migrate seasonally as revealed by radar monitoring [10] and isotopic tools 54 [11]. Population genetic analysis is also frequently employed to reveal the migration of 55 species as a complementary approach to traditional methods [12][13][14][15]. In populations of the 56 hoverflies Cheilosia longula [16], Blera fallax [17], Sphaerophoria scripta and Episyrphus 57 balteatus [18], population genetic differentiation has not been found between some regions, 58 suggesting migratory movements of these hoverflies between regions including southern 59 and northern regions of Europe [18, 19]. However, some hoverflies, such as E. balteatus 60 and Scaeva selenitica, are only partially migratory [20]. 61 Previous studies reported that E. corollae is a highly migratory species in Europe [21-62 23], but its migratory behavior of E. corollae remains unclear in other areas. E. corollae is 63 commonly found across China, but the ecology and biology of this species has rarely been 64 studied [8]. In this study, we conducted a preliminary examination of the population genetic 65 structure of E. corollae in China. First, we obtained random genomic sequences of E. 66 corollae using next-generation sequencing and developed an...