PARENT SESSION
Poster Session # 9: Herbivory.
Tuesday, August 5 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.
Leafminer damage to eastern leatherwood (Dirca palustris) in relation to plant spacing and size.
Burleyson, Travis*,1, Albrecht, Stephanie1, Schulz, Kurt1, Zasada, John2, Mattson, William3, 1 Southern Illinois University Edwardsville, Edwardsville, IL, USA2 North Central Forest Experiment Station, Grand Rapids, MN, USA3 North Central Forest Experiment Station, Rhinelander, WI, USA
ABSTRACT- Eastern leatherwood (Dirca palustris) is a small, very shade tolerant deciduous shrub that inhabits Acer saccharum -- Tsuga canadensis forests of the western Great Lakes Region. Leatherwood populations tend to be strongly aggregated owing to limited seed dispersal. With one exception, leatherwood foliage is strikingly unattractive to mammalian and insect herbivores. Larvae of the moth Leucanthiza dircella mine the leaves during midsummer. Leaf damage can be very extensive, resulting in the loss of whole leaves and significant fractions of total leaf surface (>20%) by late July. Loss of photosynthetic surface in dark forest understories has potential impacts on survivorship, growth, and reproduction. We examined how rates of leaf damage were affected by two variables (1) distance to nearest congener, and (2) size of the target individual. Our hypotheses were that increasing distance would be associated with lower damage rates, and that smaller individuals would experience higher damage rates. There were strong effects of stand identity on the role of plant spacing. In one stand herbivory rates were negligible (<0.5% leaf area); in a second stand herbivory increased with distance; in a third stand herbivory declined with distance. Landscape level variation in leaf miner populations apparently overrides the influence of spacing within leatherwood populations. Herbivory rates did not vary with respect to plant size. Smaller individuals did, however, experience a wider variance in the level of herbivory among leaves on single shrubs. Wider variance is likely associated with larger numbers of severely damaged leaves that may subsequently be lost.
Key words: Leucanthiza dircella, herbivory, Dirca palustris, leaf miner