Abstract Detail


Assour, Hannah [1], Turcotte, Martin [2], Ashman, Tia-Lynn [3].

Herbivory and plant polyploidy: How population dynamics of both partners change after whole-genome duplication.

Whole Genome Duplication (WGD), or polyploidy, is a common and important mutational process in the evolution of angiosperms, with most angiosperms having polyploidy in their evolutionary history. Polyploidy arises via either genome duplication within a single species (autopolyploidy), or hybridization between species (allopolyploidy). It is expected that most individuals go extinct after polyploidization due to the many challenges associated with WGD, yet polyploids are still widespread across plants, begging the question of what drives polyploid establishment in nature. When genome duplication occurs, the ‘gigas’ effect leads to polyploid organisms often being larger bodied than their diploid progenitors, among other phenotypic differences. What is unclear, however, is whether these phenotypic changes are the direct results of WGD or subsequent evolution, and whether variation at the population level has cascading effects on plant-herbivore dynamics. That is, does plant polyploidy alter the population growth rates and biomass production of either the plant or the herbivore during plant-herbivore interactions? To answer these questions, we conducted a fully randomized, factorial experiment comparing the effects aphid herbivory on synthetic neopolyploid plants and their immediate diploid progenitors, using duckweed and the aphids as our model system. Both the greater duckweed (Spirodela polyrhiza) and the water-lily aphid (Rhopalosiphum nymphaeae) are fast-growing organisms, and thus multiple generations can be produced within several weeks. Since they both primarily reproduce asexually, we can directly compare the effects of WGD on different genetically independent origins of polyploidy. Specifically, we compared the growth rates, tolerance levels and resistance (using abundance and biomass measures) of diploid and synthetic neopolyploid duckweed, both with and without aphid herbivores, in the growth chamber. We found that polyploid plants performed as well or worse under aphid herbivory as compared to their diploid progenitors. We also found that diploids were more tolerant (able to reduce the effect of herbivory on growth) to aphid herbivory than polyploids. However, these results varied with genotype, indicating that the effect of polyploidy depends on the genetic origin of the plant. As an explanation, it is possible that the polypoid plants are investing in other mechanisms, such as alternate life-history strategies (i.e. “seedbanking”, or turion production in duckweed), or secondary defense mechanisms (i.e., anthocyanins) to reduce herbivory. Alternatively, polyploidy may not confer any additional tolerance or resistance, but instead may be a facilitator of herbivore success and potential range expansion. These results will help us understand the mechanisms behind polyploid establishment and success and allow us to tease apart the cascading effects of polyploidy on species interactions.

1 - University of Pittsburgh, 4249 Fifth Avenue, 215 Clapp Hall, Pittsburgh, PA, 15213, United States
2 - University of Pittsburgh, 4249 Fifth Avenue, Clapp Hall, Pittsburgh, PA, 15213, United States
3 - University of Pittsburgh, Biological Sciences, 4249 Fifth Ave, Pittsburgh, PA, 15260, USA

whole-genome duplication
relative growth rate
functional traits

Presentation Type: Poster
Number: PEC016
Abstract ID:778
Candidate for Awards:Phytochemical Best Poster Award

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