Ontogenetic shift from aposematism and gregariousness to crypsis in a Romaleid grasshopper

Traits of chemically-defended animals can change as an individual grows and matures, and both theoretical and empirical evidence favour a direction of change from crypsis to aposematism. This study examines the suite of traits involved in an unusual opposite shift from aposematism to crypsis in a ne...

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Bibliographic Details
Published in:PloS one 2020-08, Vol.15 (8), p.e0237594
Main Author: Despland, Emma
Format: Article
Language:English
Subjects:
Adults
Agglomeration
Animal behavior
Animal defenses
Animals
Aposematism
Behavior
Biology and Life Sciences
Chemical defense
Crypsis
Feeds
Grasshoppers
Host plants
Hypotheses
Insects
Life history
Locomotion
Medicine and Health Sciences
Ontogeny
Physiological aspects
Social Sciences
Thermoregulation
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Summary:Traits of chemically-defended animals can change as an individual grows and matures, and both theoretical and empirical evidence favour a direction of change from crypsis to aposematism. This study examines the suite of traits involved in an unusual opposite shift from aposematism to crypsis in a neotropical toxic-plant-feeding Romaleid grasshopper, Chromacris psittacus (Gerstaecker, 1873). Field surveys, behavioural observations and a rearing experiment compare host plant choice, aggregation, locomotion and thermoregulation between life history stages. Results showed that both nymphs and adults fed exclusively on a narrow range of Solanaceae plants, suggesting that the shift in defensive syndrome is not due to a change in chemical defense. Instead, nymphal aposematism appears linked to aggregation in response to plant-based selection pressures. Slow nymphal development suggests a cost to feeding on toxic plant compounds, and grouping could mitigate this cost. Grouping also increases conspicuousness, and hence can favour warning colourating in chemically-defended insects. The role of diet breadth in aposematism is poorly understood, and these results suggest how constraints imposed by feeding on toxic plants can generate bottom-up selection pressures shaping the adaptive suites of traits of chemically-defended animals.
ISSN:1932-6203
1932-6203
DOI:10.1371/journal.pone.0237594