Canadian Forest Service Publications

Plant-herbivore interactions in a trispecific hybrid swarm of Populus: assessing support for hypotheses of hybrid bridges, evolutionary novelty and genetic similarity. Floate, K.D.; Godbout, J.; Lau, M.K.; Isabel, N.; Whitham, T.G. 2016. New Phytol. 209:832-844.

Year: 2016

Issued by: Laurentian Forestry Centre

Catalog ID: 36528

Language: English

Availability: PDF (request by e-mail)

Available from the Journal's Web site.
DOI: 10.1111/nph.13622

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Mark record


  • Natural systems of hybridizing plants are powerful tools with which to assess evolutionary processes between parental species and their associated arthropods. Here we report on these processes in a trispecific hybrid swarm of Populus trees.

  • Using field observations, common garden experiments and genetic markers, we tested the hypothesis that genetic similarities among hosts underlie the distributions of 10 species of gall-forming arthropods and their ability to adapt to new host genotypes.

  • Key findings: the degree of genetic relatedness among parental species determines whether hybridization is primarily bidirectional or unidirectional; host genotype and genetic similarity strongly affect the distributions of gall-forming species, individually and as a community. These effects were detected observationally in the wild and experimentally in common gardens; correlations between the diversity of host genotypes and their associated arthropods identify hybrid zones as centres of biodiversity and potential species interactions with important ecological and evolutionary consequences. 

  • These findings support both hybrid bridge and evolutionary novelty hypotheses. However, the lack of parallel genetic studies on gall-forming arthropods limits our ability to define the host of origin with their subsequent shift to other host species or their evolution on hybrids as their final destination.

Plain Language Summary

The results of this study highlight the significant potential for diversity in zones where three species of poplar (P. balsamifera, P. angustifolia and P. deltoids) crossbreed (i.e., hybridize).

This study focused on the impacts of the presence of hybrids between these three types of poplar at the stand level, as well as at the level of arthropod communities (invertebrate animals such as insects, spiders, etc.), which are highly host-specific. Genetic markers were used to categorize the trees sampled according to their degree of hybridization.

By studying arthropod communities, researchers were able to show that the more poplar species hybridize, the more they share arthropod species. Hence, the diversity of arthropods increased with the prevalence of hybrids in the stand. Furthermore, a specific species of arthropod was found exclusively on hybrid trees, thus proving that hybrids can be a source of biodiversity.