Disjunction between canola distribution and the genetic structure of its recently described pest, the canola flower midge (Contarinia brassicola)

Abstract

Population genomics is a useful tool in the integrated pest management toolbox for elucidating population dynamics, demography, and histories of invasion. However, next-generation sequencing approaches can be hampered by low DNA input from small organisms, such as insect pests. Here, we use a restriction-site associated DNA sequencing approach combined with whole-genome amplification to assess genomic population structure of a newly described pest of canola, the diminutive canola flower midge, Contarinia brassicola. We find that whole-genome amplification prior to library preparation caused a reduction in the overall number of loci sequenced and an increase in overall sequencing depth but had no discernable impact on genotyping consistency for population genetic analysis. Clustering analyses recovered little geographic structure across the main canola production region, but differentiated several geographically disparate populations at edges of the agricultural zone. Given a lack of alternative hypotheses for this pattern, we suggest these data support alternative hosts for this species and thus our canola-centric view of this midge as a pest has limited our understanding of its biology. These results speak to the need for increased surveying effort across multiple habitats and other potential hosts within Brassicaceae, to elucidate both our ecological and evolutionary knowledge of this species as well as potential management implications.

Cost‐saving population genomic investigation of Daphnia longispina complex resting eggs using whole‐genome amplification and pre‐sequencing screening

“…When using WGA strategies, it is also important to consider the impact of the quantity of input DNA that can lead to downwardly biased estimates of heterozygosity and therefore genotyping bias (Medeiros & de Medeiros & Farrell, 2018). This study and others that use very small amounts of input DNA (Campbell et al, 2020; Cruaud et al, 2018; O'Grady et al, 2021) indicate that MDA‐WGA does not introduce amplification bias that affects SNP genotyping. It is also suitable for structural variant calling with the exception of inversions (Lack et al, 2018).…”

Distribution and life history of Contarinia brassicola (Diptera: Cecidomyiidae) in canola (Brassica napus) grown on the Canadian Prairies

“…C. brassicola is hypothesized to be native to North America (Mori et al, 2019). An analysis of the population genetics of C. brassicola larvae collected from canola fields in Alberta, Saskatchewan, and Manitoba supports this conclusion (Campbell et al, 2020). In preliminary studies, C. brassicola females were found to oviposit on developing canola flower buds and larval feeding inside the buds resulted in galled flowers that did not produce pods or seeds.…”

“…Additional sampling in Manitoba, as well as farther east in Canada (e.g., Ontario, Quebec) and in areas where canola is grown in the United States is required to fully delineate the North American distribution of C. brassicola . At present, we hypothesize that C. brassicola is native to North America (Campbell et al, 2020; Mori et al, 2019); however, further research is needed to determine if C. brassicola is present in other canola (oilseed rape) growing regions in the world.…”