PARENT SESSION
Wednesday, August 9, 8:00-11:30 am
COS 50 - Effects of herbivory I
L-2, Lobby Level, Cook Convention Center
Presiders: C Ivey

Inducible plant responses link foliar and root herbivore communities.

Kaplan, Ian^*,1, Sardanelli, Sandra¹, Denno, Robert¹, ¹ University of Maryland, College Park, MD

ABSTRACT- Virtually all terrestrial plants possess both aboveground and belowground components (shoots and roots) that respond to their respective environments. Accordingly, factors that influence how plants uptake water and nutrients in their roots should have a strong impact on organisms associated with shoots. Similarly, heterotrophs that interfere with aboveground photosynthetic processes can indirectly alter the structure of belowground food webs. As a result, plants serve as a conduit linking the dynamics of two spatially separated communities. Here, we explore indirect interactions between above- and belowground herbivores associated with tobacco (Nicotiana tabacum). A diverse assemblage of herbivorous insects consumes aboveground tobacco foliage, whereas roots are persistently attacked by phytoparasitic nematodes. Since nematodes are predominantly soil-dwelling organisms and insects mostly consume aboveground foliage, the two herbivore groups have virtually no opportunity for direct encounter and therefore any interactions must be indirect and mediated through phenotypic changes in their shared host-plant. Through experimental insect and nematode manipulations performed in greenhouse and field settings we document interactions connecting these two important groups of plant parasites. Specifically, root herbivory resulted in positive effects on the performance of leaf-chewing caterpillars, while generating strong suppressive effects on aphid population growth. Aboveground caterpillar herbivory facilitated root-feeding herbivores, promoting a significant increase in nematode fecundity. Notably, this facilitative effect disappeared when the same amount of foliar tissue was removed using simulated defoliation. These results emphasize the substantial interconnections that link the dynamics of aboveground and belowground communities via herbivore-induced plant responses.

Key words: herbivory, community ecology, above/belowground interactions