Submission Type

Poster

Abstract

Polyploidy, or whole-genome duplication, is a widespread mutational process in plants with a myriad of phenotypic and genotypic consequences. In addition to consequences incurred by the plant, polyploidy can potentially cascade to alter species interactions. Yet, knowledge of whether ploidy-induced variation has effects on plant-herbivore dynamics is scarce. Here, we test whether aphid herbivores exhibit preference for a diploid or polyploid host cytotype and whether ploidy impacts plant resistance and tolerance to aphids, measured as aphid and plant performance respectively. To answer these questions, we evaluated aphid choice and compared the effects of the water-lily aphid (Rhopalosiphum nymphaeae) herbivore on multiple independently synthesized lines of neopolyploid greater duckweed (Spirodela polyrhiza) and their immediate diploid progenitors in growth chamber experiments. Both aphids and duckweeds are fast-growing organisms, producing multiple asexual generations within several weeks, providing a unique opportunity to evaluate population growth rates of both partners during their interaction. We found that aphids generally preferred polyploid duckweed over their diploid progenitors. We also found that polyploid plants performed as well or worse under aphid herbivory compared to their diploid progenitors. Similarly, aphid growth rates were either the same or higher on polyploid plants. Thus, polyploid plants exhibited lower tolerance and resistance than their diploid progenitors. However, these results varied by genotype, indicating that the effect of polyploidy depends on the plant’s genetic origin. Consequently, it is possible that plant polyploidy may not confer any higher tolerance or resistance to herbivory. Instead, plant polyploidy may contribute to herbivore success and host range expansion, eventually promoting evolutionary diversification of the herbivore.

Comments

Martin Turcotte1, Tia-Lynn Ashman1

1University of Pittsburgh, Department of Biological Sciences

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Polyploidy’s impact on plant-herbivore dynamics: Evidence from experiments with water-lily aphids and greater duckweed

Polyploidy, or whole-genome duplication, is a widespread mutational process in plants with a myriad of phenotypic and genotypic consequences. In addition to consequences incurred by the plant, polyploidy can potentially cascade to alter species interactions. Yet, knowledge of whether ploidy-induced variation has effects on plant-herbivore dynamics is scarce. Here, we test whether aphid herbivores exhibit preference for a diploid or polyploid host cytotype and whether ploidy impacts plant resistance and tolerance to aphids, measured as aphid and plant performance respectively. To answer these questions, we evaluated aphid choice and compared the effects of the water-lily aphid (Rhopalosiphum nymphaeae) herbivore on multiple independently synthesized lines of neopolyploid greater duckweed (Spirodela polyrhiza) and their immediate diploid progenitors in growth chamber experiments. Both aphids and duckweeds are fast-growing organisms, producing multiple asexual generations within several weeks, providing a unique opportunity to evaluate population growth rates of both partners during their interaction. We found that aphids generally preferred polyploid duckweed over their diploid progenitors. We also found that polyploid plants performed as well or worse under aphid herbivory compared to their diploid progenitors. Similarly, aphid growth rates were either the same or higher on polyploid plants. Thus, polyploid plants exhibited lower tolerance and resistance than their diploid progenitors. However, these results varied by genotype, indicating that the effect of polyploidy depends on the plant’s genetic origin. Consequently, it is possible that plant polyploidy may not confer any higher tolerance or resistance to herbivory. Instead, plant polyploidy may contribute to herbivore success and host range expansion, eventually promoting evolutionary diversification of the herbivore.