Aphid and ladybird beetle abundance depend on the interaction of spatial effects and genotypic diversity

Abstract

Intraspecific variation and genotypic diversity of host-plants can affect the structure of associated arthropod communities and the dynamics of populations. Similarly, neighboring plants can also affect interactions between host-plants and their associated arthropods. However, most studies on the effects of host-plant genotypes have largely ignored the potential effects of neighboring host-plants on arthropod communities. In this study, we used a common garden experiment to ask how spatial effects of neighboring patches, along with genotype identity and genotypic diversity in tall goldenrod (Solidago altissima), affect the abundances of a common goldenrod herbivore (Uroleucon nigrotuberculatum) and their dominant predator (Harmonia axyridis, a ladybird beetle). Aphid abundance varied 80-fold among genotypes, while ladybird beetle abundance was not affected by genotype identity. Additionally, there were strong effects of neighboring plots: aphid abundance in a focal plot was positively correlated to aphid abundance in nearby plots, suggesting strong spatial patterning in the abundance of aphids. Neither aphid nor ladybird beetle abundance was affected by genotypic diversity. However, focal plot genotypic diversity mediated the strength of the neighborhood effect (i.e., strong effects for genotype polyculture focal plots and weak effects for genotype monoculture focal plots). Our results show that aphids were directly influenced by host-plant genotype identity while ladybird beetles responded mainly to prey abundance, and suggest that genotypic diversity can influence the effects of spatial processes on the plant-herbivore interactions.

Defensive chemicals of neighboring plants limit visits of herbivorous insects: Associational resistance within a plant population

“…Thus, defensive traits of individuals may scale up to a population level, making it important to account for how contrasting genotypes affect population dynamics. Furthermore, recent studies demonstrated that intraspecific plant genetic diversity can act as an important factor in shaping herbivore communities on plants (Cook‐Patton, McArt, Parachnowitsch, Thaler, & Agrawal, , Genung et al, , Crawford and Rudgers 2013). Exploring the precise plant‐herbivore interactions in nature thus requires further attention to the scope of neighborhood effects mediated by defensive traits and their genotypic variations in a spatial context.…”

“…Similar arguments on associational effects would also apply to intraspecific interaction, that is, interactions among conspecific plants with different phenotypes and/or genotypes (Champagne et al, ; Coverdale, Goheen, Palmer, & Pringle, ). For example, within a population of Solidago altissima , genotypic diversity of co‐occurring plants decreased herbivory on the focal plants (i.e., associational resistance), although the mechanism was unclear (Genung, Crutsinger, Bailey, Schweitzer, & Sanders, ). Thus, a spatial perspective should be critical for better understanding the effects of plant defensive traits and plant‐herbivore interactions in a population context (Agrawal, Lau, & Hambäck, ; Ohgushi & Hambäck, ).…”

Chilades pandava Damage among 85 Cycas Species in a Common Garden Setting

“…Therefore, disparity in timing of ovipositioning among Cycas species within close proximity may influence the attraction of subsequent gravid female butterflies. Moreover, genotype of neighboring plants may influence herbivore abundance on focal plants (Genung et al, 2012). Consequently, herbivory of an individual Cycas tree within a common garden setting may be influenced by layout of the species within the planting.…”

Evidence that ERF transcriptional regulators serve as possible key molecules for natural variation in defense against herbivores in tall goldenrod

“…The nature of intraspecific genetic variations of S. altissima that contribute to its environmental adaption has been intensively studied during the last decade [5][6][7][8]25 . Although it is clear that herbivory pressure is closely linked to S. altissima polymorphism 26,27 , the responsible regulatory factor(s) have not yet been identified.…”