title: Translating environmental gradients into discontinuous reaction norms via hormone signalling in a polyphenic butterfly.
abstract: Polyphenisms-the expression of discrete phenotypic morphs in response to environmental variation-are examples of phenotypic plasticity that may potentially be adaptive in the face of predictable environmental heterogeneity. In the butterfly Bicyclus anynana, we examine the hormonal regulation of phenotypic plasticity that involves divergent developmental trajectories into distinct adult morphs for a suite of traits as an adaptation to contrasting seasonal environments. This polyphenism is induced by temperature during development and mediated by ecdysteroid hormones. We reared larvae at separate temperatures spanning the natural range of seasonal environments and measured reaction norms for ecdysteroids, juvenile hormones (JHs) and adult fitness traits. Timing of peak ecdysteroid, but not JH titres, showed a binary response to the linear temperature gradient. Several adult traits (e.g. relative abdomen mass) responded in a similar, dimorphic manner, while others (e.g. wing pattern) showed a linear response. This study demonstrates that hormone dynamics can translate a linear environmental gradient into a discrete signal and, thus, that polyphenic differences between adult morphs can already be programmed at the stage of hormone signalling during development. The range of phenotypic responses observed within the suite of traits indicates both shared regulation and independent, trait-specific sensitivity to the hormone signal.
authors.affiliation: Institute of Biology, Leiden University, Leiden, The Netherlands. v.oostra@biology.leidenuniv.nl
authors.forename: Vicencio
authors.initials: V
authors.lastname: Oostra
authors.forename: Maaike A
authors.initials: MA
authors.lastname: de Jong
authors.forename: Brandon M
authors.initials: BM
authors.lastname: Invergo
authors.forename: Fanja
authors.initials: F
authors.lastname: Kesbeke
authors.forename: Franziska
authors.initials: F
authors.lastname: Wende
authors.forename: Paul M
authors.initials: PM
authors.lastname: Brakefield
authors.forename: Bas J
authors.initials: BJ
authors.lastname: Zwaan
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000818:Animals; D002080:Butterflies / Q000502:physiology*; D026461:Ecdysteroids / Q000378:metabolism; D017753:Ecosystem; D005260:Female; D007605:Juvenile Hormones / Q000378:metabolism; D008297:Male; D010675:Pheromones; D011679:Pupa; D012621:Seasons; D013696:Temperature
chemical_list: D026461:Ecdysteroids; D007605:Juvenile Hormones; D010675:Pheromones
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