Search for: All records

Abstract The painted lady butterfly, Vanessa cardui, has the longest migration routes, the widest hostplant diversity, and one of the most complex wing patterns of any insect. Due to minimal culturing requirements, easily characterized wing pattern elements, and technical feasibility of CRISPR/Cas9 genome editing, V. cardui is emerging as a functional genomics model for diverse research programs. Here, we report a high-quality, annotated genome assembly of the V. cardui genome, generated using 84× coverage of PacBio long-read data, which we assembled into 205 contigs with a total length of 425.4 Mb (N50 = 10.3 Mb). The genome was very complete (single-copy complete Benchmarking Universal Single-Copy Orthologs [BUSCO] 97%), with contigs assembled into presumptive chromosomes using synteny analyses. Our annotation used embryonic, larval, and pupal transcriptomes, and 20 transcriptomes across five different wing developmental stages. Gene annotations showed a high level of accuracy and completeness, with 14,437 predicted protein-coding genes. This annotated genome assembly constitutes an important resource for diverse functional genomic studies ranging from the developmental genetic basis of butterfly color pattern, to coevolution with diverse hostplants. 

Rapid environmental change can decouple previously reliable cues from important resources, causing specialized recognition systems to result in maladaptive behaviors. For native herbivorous insects, such evolutionary traps are often imposed by attractive invasive plants that prove harmful to their offspring. Despite the costs of ovipositing on a poor‐quality host, evolutionary traps are expected to persist when overlapping cue sets (cue similarity) link decreased preference for the novel, unsuitable plant with decreased preference for the historical or native resource. We evaluated the role of cue similarity in the persistence of maladaptive oviposition by a native butterfly on a lethal, invasive mustard. While the novel plant shares glucosinolate cues with at least one of the native hosts and the most abundant cue is a strong oviposition stimulant, we found that this cue was not a major driver of preference for either plant. Nor was preference for the two plants correlated, meaning decreased preference for the invasive mustard would not cause butterflies to miss potential oviposition opportunities on the superior native host. Instead, butterfly preference was modified by previous experience in a way that suggests that frequent encounters with native hosts in the wild may buffer butterflies against this evolutionary trap.

 

Evolutionary traps arise when organisms use novel, low‐quality or even lethal resources based on previously reliable cues. Persistence of such maladaptive interactions depends not only on how individuals locate important resources, such as host plants, but also the mechanisms underlying poor performance.Pieris macdunnoughii(Remington) (Lepidoptera: Pieridae) lays eggs on a non‐native mustard,Thlaspi arvense(L.) (Brassicaceae), which is lethal to the larvae. We first tested whether larval feeding behavior was affected before (pre‐) ingestion or following (post‐) ingestion of leaf material, indicating activity of feeding deterrents, toxins, or both in this evolutionary trap. Neonates were less likely to start feeding and eventually fed more slowly onT. arvensethan on the native host plantCardamine cordifolia(Gray) (Brassicaceae) in both laboratory and field. Starvation was a primary cause of mortality, indicating the role of a feeding deterrent. Feeding did not differ between larvae from invaded and uninvaded population. Second,T. arvensedefensive chemistry is dominated by the glucosinolate sinigrin (allyl or 2‐propenyl glucosinolate). Adding sinigrin to the leaves ofT. arvenseand native hostsC. cordifoliaandDescurainia incana(Bernhardi ex Fischer & Meyer) (Brassicaceae) delayed the onset of feeding, caused larvae to feed more slowly, and decreased survival on the native hosts. This evolutionary trap may not be driven by a novel deterrent, but rather by a change in the concentration of a deterrent found in native hosts. Many insects have adapted to evolutionary traps posed by invasive plants, incorporating the new plant into their diets.Thlaspi arvenseremains lethal toP. macdunnoughii, and pre‐ingestive deterrents such as excess sinigrin may contribute to persistent maladaptation.