Assessing genomic admixture between cryptic Plutella moth species following secondary contact

Abstract

Cryptic species are genetically distinct taxa without obvious variation in morphology and are occasionally discovered using molecular or sequence datasets of populations previously thought to be a single species. The world-wide Brassica pest, Plutella xylostella (diamondback moth), has been a problematic insect in Australia since 1882, yet a morphologically cryptic species with apparent endemism (P. australiana) was only recognized in 2013. Plutella xylostella and P. australiana are able to hybridize under laboratory conditions, and it was unknown whether introgression of adaptive traits could occur in the field to improve fitness and potentially increase pressure on agriculture. Phylogenetic reconstruction of 29 nuclear genomes confirmed P. xylostella and P. australiana are divergent, and molecular dating with 13 mitochondrial genes estimated a common Plutella ancestor 1.96±0.175 MYA. Sympatric Australian populations and allopatric Hawaiian P. xylostellapopulations were used to test whether neutral or adaptive introgression had occurred between the two Australian species. We used three approaches to test for genomic admixture in empirical and simulated datasets including i) the f3 statistic at the level of the population, ii) pairwise comparisons of Nei's absolute genetic divergence (d XY ) between populations and iii) changes in phylogenetic branch lengths between individuals across 50 kb genomic windows. These complementary approaches all supported reproductive isolation of the Plutella species in Australia, despite their ability to hybridize. Finally, we highlight the most divergent genomic regions between the two cryptic Plutella species and find they contain genes involved with processes including digestion, detoxification and DNA binding.

An Insect Counteradaptation against Host Plant Defenses Evolved through Concerted Neofunctionalization

“…The gene branching order indicated that the initial SulfC duplication, resulting in GSS3 and GSS1/2 , occurred early in the Plutella lineage, whereas the subsequent duplication of GSS1/2 , leading to PxGSS1 and PxGSS2 , likely took place after the P. xylostella and P. australiana lineages diverged from a common ancestorabout two Ma (Ward and Baxter 2018). Because all three GSS genes in the DBM genome, PxGSS1 , PxGSS2 , and PxGSS3 , coded for enzymes with GSS activity, we deduced that this activity had emerged before SulfC duplicated in the Plutella lineage.…”

Genome-wide analysis of diamondback moth, Plutella xylostella L., from Brassica crops and wild host plants reveals no genetic structure in Australia

“…Although these species can hybridize in laboratory crosses, whether hybridization occurs in the wild is unknown 35 . Whole genome analysis of 29 Plutella individuals found no evidence for widespread introgression between these two species 59 . In our study, all Esperance and Southend individuals exhibited levels of heterozygosity across > 550,000 variant and invariant genome-wide loci that were similar to other P. xylostella .…”

The complete mitochondrial genome of Monopis longella Walker, 1863 (Lepidoptera: Tineidae)

“…No potential conflicts of interest are reported by the authors. (Chen, Jiang, et al 2019); Gibbovalva kobusi, MK956103 (Chen, Liao, et al 2019); Phyllocnistis citrella, MN792920 (Liu et al 2020); Corythoxestis sunosei, MT611524 (Zhang et al 2020); Plutella xylostella, JF911819 and KM023645 (Wei et al 2013;Dai et al 2016); Plutella australiana, MG787473 (Wardz and Baxter 2018); Leucoptera malifoliella, JN790955 (Wu et al 2012); Lyonetia clerkella, MF045483 (Unpublished); Prays oleae, KM874804 (van Asch et al 2016); Astrotischeria sp., KJ508056 (Timmermans et al 2014); Stigmella roborella, KJ508054 (Timmermans et al 2014).…”

“…and Stigmella roborella) were included as an outgroup. GenBank accession numbers of the species analyzed are as follows: Amorophaga japonica, MH823253 (Kim et al 2020); Tineola bisselliella, KJ508045 (Timmermans et al 2014); Eumeta variegata, MH574939 (Jeong et al 2018); Mahasena colona, KY856825 (Li et al 2017); Dahlica ochrostigma, MK890245 (Roh et al 2019); Acanthopsyche nigraplaga, MT883999 (Lee et al 2021); Eudarcia gwangneungensis, MN413148 (Roh et al 2020); Phyllonorycter froelichiella, KJ508048 (Timmermans et al 2014); Phyllonorycter platani, KJ508044(Timmermans et al 2014); Cameraria ohridella, KJ508042(Timmermans et al 2014); Caloptilia theivora, MK541932(Chen, Jiang, et al 2019); Gibbovalva kobusi, MK956103(Chen, Liao, et al 2019); Phyllocnistis citrella, MN792920(Liu et al 2020); Corythoxestis sunosei, MT611524(Zhang et al 2020); Plutella xylostella, JF911819 and KM023645(Wei et al 2013;Dai et al 2016); Plutella australiana, MG787473(Wardz and Baxter 2018); Leucoptera malifoliella, JN790955(Wu et al 2012); Lyonetia clerkella, MF045483 (Unpublished); Prays oleae, KM874804 (van Asch et al 2016); Astrotischeria sp., KJ508056(Timmermans et al 2014); Stigmella roborella, KJ508054(Timmermans et al 2014).…”