Graduate Faculty Memberships
Ecology, Evolution and Behavior; Conservation Biology
Ecology, specifically the interactions of plants with insects and mycorrhizae and plant resource allocation.
Plants can't move to a nicer spot if their environment turns nasty. And environment is periodically nasty. The theme that binds together the biological systems in which I have worked is my interest in how plants deal with stress -- six month droughts; rain forest floors where the only useful light is sunflecks; defoliating insects, nutrient impoverished soils.
The interactions of plants and insects has claimed my attention longest. In Australia I asked whether insects influence the distributions of the dominant genus of forest trees. Eucalypts sustain chronically high levels of insect attack, and tree-rings, field experiments and historical records show that insects consistently depress growth of some species more than others. Why? The answer(s) may involve seasonal growth patterns, low leaf nutrient content, low generic diversity of forests, frequency of hybrid zones which may facilitate easy expansion of host range by insects, or the size of insectivorous bird populations.
In North America, insect damage is less noticeable because it is episodically heavy but patchy, or levels appear low to us so that we do not appreciate the cumulative impacts that affect plants' ability to compete with neighbors. I have used a glodenrod-insect system to explore the role of spatial distribution of host plants on the ability of specialized insect to locate them and the cues insects use to find hosts in complex communities. Most recently I have asked how goldenrod clones can disappear following defoliation and reappear 1 to 13 years later. The answer may involve changes in resource allocation pattern or interactions with mycorrhizae that connect them to other plant species.
My students work on these and other projects ranging from effects of nitrogen deposition on community structure of mycorrhizal communities and responses of insect communities to climatic change.
Preus, L.E. and P.A. Morrow. 1999. Direct and indirect effects of two herbivore species on resource allocation in their shared host plant: The rhizome galler Eurosta comma, the folivore Trirhabda canadensis, and Solidago missouriensis. Oecologia 119:219-226.
Morrow, P.A., T.G. Whitham, B.M. Potts, P. Ladiges, D.H. Ashton and J.B. Williams. 1994. Gall-forming insects concentrate on hybrid phenotypes of Eucalyptus hosts. In The Ecology and Evolution of Gall-Forming Insects. 1994. P.W. Price, W.J. Mattson and Y.N. Baranchikov, eds. USDA General Technical Report NC-174. pp. 121-134.
Whitham, T.G., P.A. Morrow, and B.M. Potts. 1994. Plant hybrid zones as centers of biodiversity: The herbivore community of two endemic Tasmanian eucalypts. Oecologia 97:481-490.
Morrow, P.A. and L.R. Fox. 1989. Estimates of pre-settlement insect damage in Australian and North American forests. Ecology 70:1055-1060.
Morrow, P.A., D.W. Tonkyn and R.J. Goldburg. 1989. Patch colonization by Trirhabda canadensis (Chrysomelidae: Coleoptera): Effects of plant species composition and wind. Oecologia 81:43-50.