Liz Wason and coauthors Anurag Agrawal and Mark Hunter published a paper on latitudinal variation in herbivore-induced emission of plant volatile compounds (VOCs). Many plants emit volatile compounds, and in many cases the emissions increase when plants are damaged by herbivores, and this is often beneficial for plants because the VOCs often attract natural enemies of herbivores. Liz and colleagues studied a common garden of milkweed plants collected from 20 populations originating across 10 degrees of latitude, and found that herbivore-induced emission of VOCs was greater at high versus low latitudes. Their work, in combination with previous studies, suggests that milkweeds do not show a pattern of greater defense against herbivores at low latitudes.
EL Wason, AA Agrawal, MD Hunter. 2013. A Genetically-Based Latitudinal Cline in the Emission of Herbivore-Induced Plant Volatile Organic Compounds. J. Chem. Ecol. 39:1101-1111.
Laurie Marczak, Kazik and Steve have a new paper in Journal of Ecology exploring how local versus geographic variation in traits of Spartina alterniflora affect herbivores (Prokelisia planthoppers). As shown before, local variation (tall versus short form, simulated in our study by fertilizing) was very important for herbivores, which do better on tall form plants. Although high-latitude plants are more palatable to herbivores than low-latitude plants, this affected population growth only slightly. Predators (spiders) and top omnivores (Orchelimum) affected Prokelisia, but these effects were mediated by bottom-up conditions. These results allow us to start putting local studies of Spartina-herbivore interactions into a better geographic context.
Marczak, L. B., K. Więski, R. F. Denno and S. C. Pennings. 2013. Importance of local versus geographical variation in saltmarsh plant quality for arthropod herbivore communities. Journal of Ecology 101:1169-1182.