PARENT SESSION
Contributed Oral Session 3: Herbivory: Plant - Herbivore Interaction
Monday, August 8, 8:00 AM - 11:30 AM, Meeting Room 513 E, Level 5, Palais des congrès de Montréal
Plant decisions and population dynamics of a cactus herbivore.
Miller, Thomas*,1, Tyre, Andrew2, 1 School of Biological Sciences, Lincoln, NE, US2 School of Natural Resources, Lincoln, NE, US
ABSTRACT- Plants are flexible in their allocation of meristems toward different life history functions. Plasticity in the production of reproductive vs. vegetative parts should have consequences for herbivores that prefer or specialize on those parts. We evaluated this prediction using the tree cholla cactus (Opuntia imbricata) and the cactus bug (Narnia pallidicornis) as a model system. We fit a stage-structured population model that incorporates cactus relative investment (RI; reproductive parts : vegetative parts) to field data using Maximum Likelihood techniques. In the most likely model structure, bug fecundity is a linear function of host plant RI. Consequently, cacti that favor reproduction over growth (RI>1) support larger bug populations. Independent data sets show strong support for model predictions across temporal and spatial scales. We tracked individual tree cholla for 2 years and found that a significant increase in relative investment was associated with a significant increase in cactus bug abundance across years. We also surveyed 5 tree cholla populations and found that among-population variation in cactus RI was strongly correlated with variation in bug abundance. Our results suggest that host plant resource allocation is a critical component of plant quality, and an important source of variation in herbivore pressure within and among plant populations.
Key words: population dynamics, plant-insect interactions, Opuntia, maximum likelihood