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Evolution of larval gregariousness is associated with host plant specialisation, but not host morphology, in Heliconiini butterflies
  • Callum McLellan,
  • Stephen Montgomery
Callum McLellan
University of Bristol

Corresponding Author:[email protected]

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Stephen Montgomery
University of Bristol
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Insect herbivores, such as lepidopteran larvae, often have close evolutionary relationships with their host plants, with which they may be locked in an evolutionary arms race. Larval grouping behaviour may be one behavioural adaptation that improves host plant feeding, but aggregation also comes with costs, such as higher competition and limited resource access. Here, we use the Heliconiini butterfly tribe to explore the impact of host plant traits on the evolution of larval gregariousness. Heliconiini almost exclusively utilise species from the Passifloraceae as larval host plants. Passifloraceae display incredible diversity of form, leaf shape and a range of anti-herbivore defences, suggesting they are locked in an arms race with Heliconiini larvae. By analysing larval social behaviour as both a binary (solitary or gregarious) and categorical (increasing larval group size) trait, we revisit the multiple origins of larval gregariousness across Heliconiini. We investigate whether host habitat, leaf defences and leaf size are important drivers of, or constraints on, larval gregariousness. Whereas our data do not reveal links between larval gregariousness and the host plant traits included in this study, we do find an interaction between larval host specialisation and behaviour, revealing gregarious larvae to be more likely to feed on a narrower range of host plant species than solitary larvae. We also find evidence that this increased specialisation typically precedes the evolutionary transition to gregarious behaviour. The comparatively greater host specialisation of gregarious larvae suggests that there are specific morphological and/or ecological features of their host plants that favour this behaviour.
27 Jun 2023Submitted to Ecology and Evolution
28 Jun 2023Assigned to Editor
28 Jun 2023Submission Checks Completed
30 Jun 2023Reviewer(s) Assigned
18 Sep 2023Review(s) Completed, Editorial Evaluation Pending
31 Oct 2023Editorial Decision: Revise Minor