The impact of life stage and pigment source on the evolution of novel warning signal traits

Carita Lindstedt, Robin K. Bagley, Sara Calhim, Mackenzie Jones, Catherine R. Linnen

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

Our understanding of how novel warning color traits evolve in natural populations is largely based on studies of reproductive stages and organisms with endogenously produced pigmentation. In these systems, genetic drift is often required for novel alleles to overcome strong purifying selection stemming from frequency-dependent predation and positive assortative mating. Here, we integrate data from field surveys, predation experiments, population genomics, and phenotypic correlations to explain the origin and maintenance of geographic variation in a diet-based larval pigmentation trait in the redheaded pine sawfly (Neodiprion lecontei), a pine-feeding hymenopteran. Although our experiments confirm that N. lecontei larvae are indeed aposematic—and therefore likely to experience frequency-dependent predation—our genomic data do not support a historical demographic scenario that would have facilitated the spread of an initially deleterious allele via drift. Additionally, significantly elevated differentiation at a known color locus suggests that geographic variation in larval color is currently maintained by selection. Together, these data suggest that the novel white morph likely spread via selection. However, white body color does not enhance aposematic displays, nor is it correlated with enhanced chemical defense or immune function. Instead, the derived white-bodied morph is disproportionately abundant on a pine species with a reduced carotenoid content relative to other pine hosts, suggesting that bottom-up selection via host plants may have driven divergence among populations. Overall, our results suggest that life stage and pigment source can have a substantial impact on the evolution of novel warning signals, highlighting the need to investigate diverse aposematic taxa to develop a comprehensive understanding of color variation in nature.

Original languageEnglish
Pages (from-to)554-572
Number of pages19
JournalEvolution
Volume76
Issue number3
DOIs
StatePublished - Mar 2022

Bibliographical note

Publisher Copyright:
© 2022 The Authors. Evolution © 2022 The Society for the Study of Evolution.

Keywords

  • Aposematism
  • carotenoids
  • chemical defense
  • ecological genetics
  • host adaptation
  • polytypic coloration

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Genetics
  • General Agricultural and Biological Sciences

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