Karina L. Silva-Brandão¹, Julia Cabral Teresa², Clécio Fernando Klitzke, Marcelo M. Brandão³, José Roberto Trigo²

1 Leibniz Institute for the Analysis of Biodiversity Change, Museum of Nature Hamburg. Martin-Luther-King-Platz 3, 20421 Hamburg, Germany. Email: This email address is being protected from spambots. You need JavaScript enabled to view it.
2 Departamento de Biologia Animal, Instituto de Biologia, Universidade Estadual de Campinas. Rua Monteiro Lobato 255, Campinas, SP, Brazil.
3 Centro de Biologia Molecular e Engenharia Genética, Universidade Estadual de Campinas. Av. Cândido Rondon, 400, Campinas, SP, Brazil.

The neotropical swallowtail butterfly Battus polydamas is a specialist on Aristolochia (Aristochiaceae). These plants are rich in natural products such as terpenoids, lignans, β-phenylethylamines (βPEA), aporphine and isoquinoline alkaloids, as well as aristolochic acids (AAs). Larvae of B. polydamas sequester some of these compounds, such as AAs, and transfer them to adults through the pupae. AAs are considered defensive compounds against natural enemies, however, the amount of AA in the larvae's diet has an effect on their performance, which may mean a cost to eating on AA-containing leaves. In the present study we evaluated the performance of B. polydamas larvae fed from 1^st instar through pupation on two host plants with different chemistry composition, A. ringens (which has several diterpenes) and A. gigantea (which has acyclic monoterpenoids and sesquiterpenoids, but no diterpenoids or AAs). Differential gene expression as response to different larval host plants was evaluated in three biological replications of gut and fat body tissues of six 5^th instar larvae. We found significant differences in the survival of larvae feeding on the two host plants; the survival in A. gigantea being significantly higher than survival in A. ringens (GLM binomial, likelihood ratio test, df = 1, χ² = 76.082, P < 0.001). In A. gigantea, 55% of the larvae persisted until pupation, while none of the larva feeding on A. ringens survived. 807 unique contigs identified by their molecular function were upregulated in the gut of larvae fed on A. ringens, while 298 were downregulated. Down-regulated contigs include genes encoding for ribosomal proteins, superoxide dismutase, P450s, UGTs, glutathione S-transferase and many proteases. Upregulated contigs comprise genes encoding for ribosomal proteins, protein farnesyltransferase, Phosphomevalonate kinase, Dolichyl-phosphate-mannose-protein mannosyltransferase 4 and O-glucosyltransferase (possibly involved in AAs metabolization). As expected, larvae of B. polydamas were strongly influenced by host plants exhibiting different concentrations of AAs, with higher concentrations leading to worse larval performance on key fitness components, such as life cycle performance attributes and larval survival. We suggest that there is a threshold of AA concentration in the host plant that larvae can tolerate, and above such a threshold the impact of plant secondary chemicals is no longer beneficial for the larvae, but negative, disrupting their detoxification mechanism.

Data availability

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