Body size as a magic trait in two plant-feeding insect species

Ashleigh N. Glover, Emily E. Bendall, John W. Terbot, Nicole Payne, Avery Webb, Ashley Filbeck, Gavin Norman, Catherine R. Linnen

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


When gene flow accompanies speciation, recombination can decouple divergently selected loci and loci conferring reproductive isolation. This barrier to sympatric divergence disappears when assortative mating and disruptive selection involve the same "magic" trait. Although magic traits could be widespread, the relative importance of different types of magic traits to speciation remains unclear. Because body size frequently contributes to host adaptation and assortative mating in plant-feeding insects, we evaluated several magic trait predictions for this trait in a pair of sympatric Neodiprion sawfly species adapted to different pine hosts. A large morphological dataset revealed that sawfly adults from populations and species that use thicker-needled pines are consistently larger than those that use thinner-needled pines. Fitness data from recombinant backcross females revealed that egg size is under divergent selection between the preferred pines. Lastly, mating assays revealed strong size-assortative mating within and between species in three different crosses, with the strongest prezygotic isolation between populations that have the greatest interspecific size differences. Together, our data support body size as a magic trait in pine sawflies and possibly many other plant-feeding insects. Our work also demonstrates how intraspecific variation in morphology and ecology can cause geographic variation in the strength of prezygotic isolation.

Original languageEnglish
Pages (from-to)437-453
Number of pages17
JournalEvolution; international journal of organic evolution
Issue number2
StatePublished - Feb 4 2023

Bibliographical note

Publisher Copyright:
© The Author(s) 2022. Published by Oxford University Press on behalf of The Society for the Study of Evolution (SSE). All rights reserved. For permissions, please e-mail:


  • Neodiprion
  • magic trait
  • plant-feeding insects
  • reproductive isolation
  • size-assortative mating
  • speciation with gene flow

ASJC Scopus subject areas

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


Dive into the research topics of 'Body size as a magic trait in two plant-feeding insect species'. Together they form a unique fingerprint.

Cite this