Preference, performance, and chemical defense in an endangered butterfly using novel and ancestral host plants

Abstract

Adoption of novel host plants by herbivorous insects can require new adaptations and may entail loss of adaptation to ancestral hosts. We examined relationships between an endangered subspecies of the butterfly Euphydryas editha (Taylor’s checkerspot) and three host plant species. Two of the hosts (Castilleja hispida, Castilleja levisecta) were used ancestrally while the other, Plantago lanceolata, is exotic and was adopted more recently. We measured oviposition preference, neonate preference, larval growth, and secondary chemical uptake on all three hosts. Adult females readily laid eggs on all hosts but favored Plantago and tended to avoid C. levisecta. Oviposition preference changed over time. Neonates had no preference among host species, but consistently chose bracts over leaves within both Castilleja species. Larvae developed successfully on all species and grew to similar size on all of them unless they ate only Castilleja leaves (rather than bracts) which limited their growth. Diet strongly influenced secondary chemical uptake by larvae. Larvae that ate Plantago or C. hispida leaves contained the highest concentrations of iridoid glycosides, and iridoid glycoside composition varied with host species and tissue type. Despite having largely switched to a novel exotic host and generally performing better on it, this population has retained breadth in preference and ability to use other hosts.

Flowering phenology influences butterfly nectar foraging on non‐native plants in an oak savanna

“…This suggests that non-native nectar is a valued resource and that butterflies may prefer non-native flowers over native flowers in some contexts, though a choice experiment could be used to determine this with greater confidence. Our results are similar to a single-species study that found ovipositing females preferred non-native plants (Euphydryas editha; Haan et al, 2021) but are unlike another single-species study that found that nectar foraging adults preferred native flowers (Plebejus icarioides fenderi; Thomas & Schultz, 2016). This reinforces the notion that studies of multiple species offer insights into general tendencies of the community.…”

‘Accidents waiting to happen’—Insights from a simple model on the emergence of infectious agents in new hosts

“…mutation rates for viruses), the phenotypic profile of the pathogen (=capacity space), although changing qualitatively and quantitatively under the selective pressure of the new host resource, putatively retain ancestral variants at low frequency in the new host (Figure 4; Figure S2). This outcome provides theoretical support for the retention of the capacity of fast-evolving pathogens to retro-colonize their previous host species by ecological fitting Haan et al, 2021;Janz & Nylin, 1998). RNA viruses, such as SARS-CoV-2, are well known to evolve rapidly through mutation and hybridization (Holland et al, 1982), and the retention of variants may facilitate retro-colonization of humans from other animal species.…”

Novel host plant use by a specialist insect depends on geographic variation in both the host and herbivore species

“…Studies comparing butterfly host plant preferences among host plant species often use plants sampled from a single source population (Wehling & Thomspon 1997 ; Ladner and Altizer 2005 ; Haan et al 2021 ; McCarty and Sotka 2013 ; c.f. Singer et al 2002 ).…”