Plant genotypic diversity increases population size of a herbivorous insect

Abstract

It is critical to incorporate the process of population dynamics into community genetics studies to identify the mechanisms of the linkage between host plant genetics and associated communities. We studied the effects of plant genotypic diversity of tall goldenrod Solidago altissima on the population dynamics of the aphid Uroleucon nigrotuberculatum. We found genotypic variation in plant resistance to the aphid in our experiments. To determine the impact of plant genotypic diversity on aphid population dynamics, we compared aphid densities under conditions of three treatments: single-genotype plots, mixed-genotype plots and mixed-genotype-with-cages plots. In the latter treatment plants were individually caged to prevent natural enemy attack and aphid movement among plants. The synergistic effects of genotypes on population size were demonstrated by the greater aphid population size in the mixed-genotype treatment than expected from additive effects alone. Two non-exclusive hypotheses are proposed to explain this pattern. First, there is a source-sink relationship among plant genotypes: aphids move from plant genotypes where their reproduction is high to genotypes where their reproduction is low. Second, natural enemy mortality is reduced in mixed plots in a matrix of diverse plant genotypes.

Plant genotypic diversity reduces the rate of consumer resource utilization

“…For example, in the most detailed study to date regarding the population response of herbivores to plant genotypic diversity, movement among plants was hypothesized to be a major driver of aphid population growth [12]. Compensatory feeding can occur when animals are restricted to diets suboptimal for their target intake of different nutrients, such as suboptimal protein : carbohydrate ratios [39,40].…”

“…At the same time, a growing body of literature suggests that genotypic diversity within species can have pronounced consequences on populations, communities and ecosystems [8]. However, while several studies have now shown that plant genotypic diversity typically increases the abundance of herbivores [9][10][11][12], how changes in herbivore abundance are linked to the consumption of plant resources remains unknown [13,14]-an important gap in our understanding of how plant diversity alters energy transfer across trophic levels.…”

“…Because movement among plants has been hypothesized to be a key mechanism altering herbivore populations in response to plant genotypic diversity [12], we conducted an experiment to explicitly evaluate P. japonica movement. We quantified movement of P. japonica within and among O. biennis patches by replicating the 2010 field establishment protocols (described above) for a follow-up experiment in 2011 containing 17 of the original 20 genotypes.…”

Influence of plant genetic diversity on interactions between higher trophic levels

“…Most studies on plant intra-and interspecific diversity have focused exclusively on the bottom-up effects of plant diversity within a single trophic level (herbivores; [8,9]), but plant diversity may also directly or indirectly affect the third trophic level, i.e. enemies and mutualists of herbivores (see [3,4,10], and the scheme represented in figure 1).…”

Evolutionary community ecology of plant‐associated arthropods in terrestrial ecosystems

“…A growing number of studies have shown that plant genotypes influence plant-arthropod interactions and community properties of plant-associated arthropods, including abundance, species richness, and species composition (Johnson and Agrawal 2005;Wimp et al 2005;Bailey et al 2006;Bangert et al 2006;Whitham et al 2006;Barbour et al 2009;Utsumi et al 2011). Both the induced plant responses and plant genetic variations are likely to have qualitatively similar effects on structuring plant-associated arthropod communities (McGuire and Johnson 2006;Utsumi et al 2009b).…”