Corresponding author: Paul K. Abram (
Academic editor: Richard Shaw
Candidate biological control agents of invasive insect pests are increasingly being found in new geographic regions as a result of unintentional introductions. However, testing the degree of genetic differentiation among adventive and native-range populations of these agents is rarely done. We used reduced-representation sequencing of genomic DNA to investigate the relationships among laboratory lines of
Abram PK, Nelson TD, Marshall V, Gariepy TD, Haye T, Zhang J, Hueppelsheuser T, Acheampong S, Moffat CE (2023) Genetic relationships among laboratory lines of the egg parasitoid
There are now numerous documented instances where natural enemies of invasive insects have been discovered following the establishment of their host or prey species, presumably as a result of unintentional introductions (
In addition to determining invasion histories, molecular techniques could determine relationships among laboratory cultures of adventive natural enemy populations that have been sourced from different regions. When applied to these ‘living genetic resources’, genetic analyses could identify distinct populations that may differ in biological attributes (e.g., host range, life history, climate tolerance) that affect establishment success and suitability as biological control agents, and could inform future introductions (e.g., to increase genetic diversity of unintentionally introduced populations) or redistributions within new geographic areas that aim to improve biological control outcomes (
Between 2017 and 2020, we established 19 laboratory lines of
Collection locations for 19 laboratory lines of
We extracted genomic DNA using DNeasy Blood and Tissue DNA kits (QIAGEN, Hilden, Germany) by following the manufacturer’s protocol, but we added a bovine ribonuclease A treatment (RNaseA, 4 uL at 100 mg/mL, QIAGEN) to digest RNA. We eluted DNA into 2× 50 uL of 56 °C Buffer AE to increase DNA concentration and yield, then we stored DNA at -20 °C until ddRAD library preparation.
Obtaining high-concentration, high-quality DNA from small-bodied organisms is an inherent challenge when preparing DNA libraries (e.g.,
The number of individual pools of 10 female wasps from each
Laboratory line | Number of pools included in dataset | ||
---|---|---|---|
full | geographic | Pacific Northwest | |
British Columbia, Canada (Langley) | 7 | – | 7 |
British Columbia, Canada (Chilliwack) | 5 | – | 5 |
British Columbia, Canada (Agassiz) | 7 | 7 | 7 |
British Columbia, Canada (Kelowna) | 7 | 7 | 7 |
Washington, USA (Vancouver) | 5 | 4 | 4 |
Washington, USA (Walla Walla) | 5 | – | 3 |
Switzerland (Basel-Stadt) | 4 | – | – |
Switzerland (Zurich) | 5 | – | – |
Switzerland (Ticino) | 5 | 5 | – |
Ontario, Canada (London, 2019–2020) | 4 | 4 | – |
Ontario, Canada (London, 2021) | 3 | – | – |
China (Beijing line 1) | 5 | – | – |
China (Beijing line 2) | 5 | – | – |
China (Beijing line 3) | 5 | 5 | – |
China (Beijing USDA line) | 4 | – | – |
China (Hebei line 1) | 5 | – | – |
China (Hebei line 2) | 4 | – | – |
China (Hebei line 3) | 5 | – | – |
China (Heilongjang) | 5 | 4 | – |
We used Stacks 2 version 2.55 (
We assessed population genetic structuring for three datasets: one containing all 19 laboratory lines (‘full dataset’), one with seven lines chosen for proportional representation of potential geographic clusters (‘geographic dataset’), and one with all six lines from the Pacific Northwest of North America (‘Pacific Northwest dataset’) (Table
DNA sequences are available as fastq files in the National Center for Biotechnology Information Sequence Read Archive (
In total, we sequenced 109 pools of
Principal component and structure analyses of SNP data from the full datasets comprising 18–19
In the geographic dataset, we retained 36 pools across the 7 laboratory lines after filtering raw reads. The dataset contained 2,896
Structure analysis of SNP data from the geographic structure dataset comprising seven
In the Pacific Northwest dataset, we retained 33 pools across the 6 laboratory lines after filtering raw reads. This dataset contained 1,976
Principal component and structure analyses of SNP data from six
Overall, we found
Among adventive
We had expected that westernmost lines from Canada and the USA (Langley, Chilliwack, Agassiz, and Vancouver, WA) would be most closely related, as would those from the interior of BC and WA (Kelowna, BC and Walla Walla, WA). Instead, both lines from Washington State are members of the same cluster despite being separated by more than 350 kilometres, providing good evidence that
Our study demonstrates that there is relatively strong population genetic structuring between
We thank Josh Milnes, Betsy Beers, and Kim Hoelmer for laboratory lines of
Supplementary information
table and figures (word document)