• Published 6 papers and one book (Princeton Univ. Press Monograph); 5 of these papers reported Archbold- based research in peer- reviewed journals including Ecology, American Journal of Botany, and Proceedings of the Entomological Society of Washington.

• Received 2 National Science Foundation grants totaling $280,000; one of these funded our oak- cynipid host-association and taxonomic studies. A travel grant from the American Museum of Natural History facilitated travel by Dr. Melika to the USA during 1998 to work on AMNH cynipid collections.

• Presented 13 talks at universities and at national and international meetings, 4 of these talks reported Archbold-based research. George Melika presented 3 talks at international meetings on Archbold- related research.

• Collaborated with James Layne on the analysis of 27 years of acorn mast data for 5 oak species (Quercus chapmanii, geminata, inopina, laevis, myrtifolia) from 4 Station habitats.

The oak stem galls induced by the wasp Callirhytis difficilis occur on Quercus inopina, Q. laevis, and Q. myrtifolia at Archbold Biological Station and the adult wasps emerge during late summer and into autumn; photo by Warren Abrahamson.

Plant-Animal Interactions and Fire Ecology

Project Director: Warren G. Abrahamson, Bucknell University
Project Assistants: Chris Abrahamson, Jill Abrahamson, Rob Scrafford
Outside Collaborators: George Melika, Systematic Parasitoid Laboratory, Koszeg, Hungary; György Csóka, Hungarian Forest Research Institute, Mátrafüred, Hungary; Jonathan M. Brown, Grinnell College

[Biennial Contents | Biennial 95-96 | Research]

Oak-Gall Inducer Studies. Gall-inducing insects gain nutrition and shelter from their host plants by altering the development of their host to form a gall. The Cynipidae (wasps) are among the most speciose families of gall inducers and almost exclusively infest oaks (Quercus). Ongoing studies are examining cynipid taxonomic and ecological relationships with their host plants. With Hungarian entomologist, George Melika, we are revising the taxonomy of this family and its genera and are describing a number of new cynipid species. Jonathan Brown (Grinnell Coll.) produced and published a preliminary generic-level phylogeny of cynipids based on mtDNA data from representative species of many genera. The strong host specificity of cynipid gallers enabled our analysis of putative phylogenetic relationships among 34 species of eastern USA oaks by comparing the cynipid communities of oak species. Funding has come from National Science Foundation, Bucknell University’s Burpee Endowment, and American Museum of Natural History.

     Palmetto Demography Studies. Understanding the role of fire in altering the growth and reproductive patterns of the plant species composing fire-adapted ecosystems is critical to natural areas management and to the preservation of biodiversity. The results of our long-term studies exploring the role of fire in the reproduction of the palmettos, Serenoa repens and Sabal etonia, will be published in Ecology (1999). [ Abrahamson, W.G. 1999. Episodic reproduction in two fire-prone palms, Serenoa repens and Sabal etonia (Palmae). Ecology 80:100-115. ] The frequency of flowering in palmettos increased dramatically following fire but the strength of the flowering response was strongly dependent on palmetto size and light availability. Additional work will determine the longevity and turnover rates of palmetto leaves. This work has been supported by Bucknell University’s Burpee Endowment and Archbold Biological Station.

     Acorn Mast Study (with J.N. Layne). The number of fruits produced by a population of woody plants can vary markedly from year-to-year. Unfortunately, knowledge of the patterns and causes of crop-size variation is limited and most studies examine only single species in single mesic associations. Annual counts of acorns were conducted at Archbold by James Layne for 27 years (1969–1996, except 1991) on two white oak species (Q. chapmanii and Q. geminata) and three red oak species (Q. inopina, Q. laevis, and Q. myrtifolia) across xeric sandhill, sand pine scrub, and scrubby flatwoods. White oak species exhibited more frequent peaks in acorn production than red oaks, however, there was no correlation of production levels for species with temperature and few weak correlations with precipitation parameters. Acorns were produced with reasonable abundance every year by at least one species. Oaks in sand pine scrub with a well-developed pine canopy produced fewer acorns than similar-sized oaks of the same species in the more open sandhill and scrubby flatwoods. Following a prescribed sandhill burn, re-sprouted white oaks produced acorns more quickly than red oaks. White oaks produced acorns during the first year following fire whereas red oaks required 3 or 4 years. to produce acorns depending on the species. The percentage of bearing individuals and the mean number of acorns/bearing individual increased with increasing plant size for all species across associations. However, in some species in some or all associations, acorn production declined in the largest size class suggesting senescence.

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