Biology subjects

Tewes, L. J.

Publications and source records attributed to Tewes, L. J..

3 recordsLinked to original sources

bioRxiv2022

Chemical defense acquired via pharmacophagy can lead to herd protection in a sawfly

Predation is an important selection pressure acting on organisms, with organisms evolving diverse anti-predator strategies to combat it. One such widespread strategy is chemical defense in which organisms either synthesize or extrinsically acquire defensive chemicals. Little is known about the intraspecific transfer of such chemicals and if such chemicals acquired from conspecifics can also serve as defense against predation. Here, we used adults of the turnip sawfly, Athalia rosae, which can acquire neo-clerodane diterpenoids ( clerodanoids) via pharmacophagy after exposure to the plant, Ajuga reptans. We show that clerodanoid access mediates protection against predation by mantids for the sawflies, both in a no-choice feeding assay and a microcosm setup. Moreover, even indirect access to clerodanoids, via nibbling on conspecifics that had access to the plant, resulted in protection against predation albeit to a much lower degree than direct access. Furthermore, sawflies that had no direct access to clerodanoids were less consumed by mantids when they were grouped with conspecifics that had direct access. Most, but not all, of such initially undefended sawflies could acquire clerodanoids from conspecifics that had direct access to the plant, although in low quantities. Together our results demonstrate that clerodanoids serve as chemical defense that can be intraspecifically transferred. Moreover, the presence of chemically defended individuals in a group can confer protection onto conspecifics that had no direct access to clerodanoids, suggesting a herd-protection effect.

ecology↗

bioRxiv2021

Consequences of pharmacophagous uptake from plants and conspecifics in a sawfly elucidated using chemical and molecular techniques

Pharmacophagy involves the sequestration of specialised plant metabolites for non-nutritive purposes and commonly occurs in insects. Here we investigate pharmacophagy in the turnip sawfly, Athalia rosae, where adults not only collect specialised metabolites (clerodanoids) from a plant (Ajuga reptans), but also from the exterior of conspecifics via fighting. Using behavioural assays, chemical analytics, and RNAseq we show that when individuals nibble on conspecifics that have already acquired clerodanoids from A. reptans leaves, this nibbling results in the transfer of compounds between individuals. Furthermore, unlike other pharmacophagous insects, the acquisition of clerodanoids by A. rosae from the leaves of A. reptans does not induce the upregulation of known detoxification or sequestration genes and pathways. In contrast, pharmacophagous nibbling on conspecifics results in the upregulation of metabolic pathways associated with elevated metabolic rates and increased energy consumption. It therefore seems that individuals attack conspecifics to acquire clerodanoids despite the apparent metabolic costs of this form of pharmacophagy compared to clerodanoid uptake from a plant. Changes in the metabolic phenotype of A.rosae individuals consequently has profound consequences for social interactions with possible ramifications for their social niche. Summary statementThe turnip sawfly (Athalia rosae) gains potentially beneficial compounds from the leaf surface of non-food plants (e.g. Ajuga reptans), but can also steal these compounds from conspecifics via aggressive nibbling.

zoology↗

bioRxiv2020

Chemical patterns of colony membership and mother-offspring similarity in Antarctic fur seals are reproducible over time

Replication studies are essential for assessing the validity of previous research findings and for probing their generality. However, it has proven challenging to reproduce the results of ecological and evolutionary studies, partly because of the complexity and lability of many of the phenomena being investigated, but also due to small sample sizes, low statistical power and publication bias. Additionally, replication is often considered too difficult in field settings where many factors are beyond the investigators control and where spatial and temporal dependencies may be strong. We investigated the feasibility of reproducing original research findings in the field of chemical ecology by attempting to replicate a previous study by our team on Antarctic fur seals (Arctocephalus gazella). In the original study, skin swabs from 41 mother-offspring pairs from two adjacent breeding colonies on Bird Island, South Georgia, were analysed using gas chromatography-mass spectrometry. Seals from the two colonies differed significantly in their chemical fingerprints, suggesting that colony membership may be chemically encoded, and mothers were also chemically similar to their pups, implying that phenotype matching may be involved in mother-offspring recognition. Here, we generated and analysed comparable chemical data from a non-overlapping sample of 50 mother-offspring pairs from the same two colonies five years later. The original results were corroborated in both hypothesis testing and estimation contexts, with p-values remaining highly significant and effect sizes, standardized between studies by bootstrapping the chemical data over individuals, being of comparable magnitude. We furthermore expanded the geographic coverage of our study to include pups from a total of six colonies around Bird Island. Significant chemical differences were observed in the majority of pairwise comparisons, indicating not only that patterns of colony membership persist over time, but also that chemical signatures are colony-specific in general. Our study systematically confirms and extends our previous findings, while also implying that temporal and spatial heterogeneity need not necessarily negate the reproduction and generalization of ecological research findings.

ecology↗