Abstract
Restoration of the functionally extirpated American chestnut (Castanea dentata) to landscapes of the eastern United States is planned with the successful propagation of a blight-resistant hybrid tree. Predicting the response of rodent seed consumers to this novel source of mast will be critical to restoration success, as rodents are important seed predators and dispersers in forests that once included chestnut. In particular, frequency-dependent foraging responses by rodents could affect the rate of spread of rare chestnuts following reintroductions. We conducted field trials to test for seed preferences and frequency-dependent selection by fox squirrels (Sciurus niger) when combinations of American chestnut and two common associates [northern red oak (Quercus rubra) and white oak (Q. alba)] were available in varying frequencies. Fox squirrels tended toward positive frequency-dependent seed predation when combinations of white oak and chestnuts were available, consuming more common mast items at a higher rate than expected based on availability. No preferences were observed between American chestnut and either red or white oak independent of frequency, but red oak was preferred over white oak. Frequency-dependent consumption of more common white oak acorns could benefit rarer chestnut during restoration, as squirrels would feed disproportionately on established white oak; however, this management strategy should only be considered following larger-scale and longer-term studies that consider impacts on white oak regeneration. Lack of preference or frequency dependence for chestnut when paired with red oak suggests that negative impacts of fox squirrel consumption on restoration will vary with the relative availability of the two seed types.
References
Abrams MD (2003) Where has all the white oak gone? Bioscience 53:927–939
Allen JA (1968) Evidence for apostatic selection by wild passerines. Nature 220:501–502
Anagnostakis SL (2012) Chestnut breeding in the United States for disease and insect resistance. Plant Dis 96:1392–1403
Bronson FH (1989) Mammalian reproductive biology. University of Chicago Press, Chicago
Burnham CR, Rutter PA, French DW (1986) Breeding blight-resistant chestnuts. Plant Breed Rev 4:347–397
Celis-Diez JL, Bustamante RO (2005) Frequency-dependent seed size selection on Cryptocarya alba (Mol.) Looser (Lauraceae): testing the effect of background. Biol J Linn Soc 84:137–142
Clark SL, Schlarbaum SE, Saxton AM, Hebard FV (2011) Making history: field testing of blight-resistant American chestnut (Castanea dentata) in the southern region. In: Fei S, Lhotka JM, Stringer JW, Gottschalk KW, Gary W (eds) Proceedings, 17th central hardwood forest conference, USDA Forest Service Northern Research Station, Lexington, pp 656–657
Dalgleish HJ, Swihart RK (2012) American chestnut past and future: implications of restoration for resource pulses and consumer populations of Eastern US Forests. Restor Ecol 20:490–497
Ellison AM, Bank MS, Clinton BD et al (2005) Loss of foundation species: consequences for the structure and dynamics of forested ecosystems. Front Ecol Environ 3:479–486
Greenwood JJ (1985) Frequency-dependent selection by seed-predators. Oikos 44:195–210
Greenwood JJ, Elton RA (1979) Analysing experiments on frequency-dependent selection by predators. J Anim Ecol 48:721–737
Hoshizaki K, Hulme PE (2002) Mast seeding and predator-mediated indirect interactions in evidence from post-dispersal fate of rodent-generated caches. In: Levey DJ, Silva WR, Galetti M (eds) Seed dispersal and frugivory: ecology, evolution and conservation. CAB International, Cambridge, pp 227–239
Hughes RN (1979) Optimal diets under the energy maximization premise: the effects of recognition time and learning. Am Nat 113:209–221
Hulme PE (1996) Herbivory, plant regeneration, and species coexistence. J Ecol 84:609–615
Hulme PE (1998) Post-dispersal seed predation: consequences for plant demography and evolution. Perspect Plant Ecol Evol Syst 1:32–46
Hulme PE, Hunt M (1999) Rodent post-dispersal seed predation in deciduous woodland: predator response to absolute and relative abundance of prey. J Anim Ecol 68:417–428
Jacobs DF, Dalgleish HJ, Nelson CD (2013) A conceptual framework for restoration of threatened plants: the effective model of American chestnut (Castanea dentata) reintroduction. New Phytol 197:378–393
Jansen PA, Bongers F, Hemerik L (2004) Seed mass and mast seeding enhance dispersal by a neotropical scatter-hoarding rodent. Ecol Monogr 74:569–589
Janzen DH (1971) Seed predation by animals. Annu Rev Ecol Syst 2:465–492
Keever C (1953) Present composition of some stands of the former oak-chestnut forest in the southern Blue Ridge Mountains. Ecology 34:44–54
Lichti NI, Steele MA, Zhang H, Swihart RK (2014) Mast species composition alters seed fate in North American rodent-dispersed hardwoods. Ecology 95:1746–1758
McShea WJ, Healy WM (2002) Oak forest ecosystems: ecology and management for wildlife. Johns Hopkins University Press, Baltimore
R Development Core Team (2011) R: a language and environment for statistical computing. R Foundation for Statistical Computing, Vienna
Steele MA, Smallwood PD (2002) Acorn dispersal by birds and mammals. In: McShea WJ, Healy WM (eds) Oak forest ecosystems: ecology and management for wildlife. Johns Hopkins University Press, Baltimore, pp 182–195
Steele MA, Turner G, Smallwood PD, Wolff JO, Radillo J (2001) Cache management by small mammals: experimental evidence for the significance of acorn embryo excision. J Mammal 82:35–42
Vander Wall SB (2001) The evolutionary ecology of nut dispersal. Bot Rev 67:74–117
Woods FW, Shanks RE (1959) Natural replacement of chestnut by other species in the Great Smoky Mountains National Park. Ecol 40:349–361
Xiao Z, Gao X, Steele MA, Zhang Z (2010) Frequency-dependent selection by tree squirrels: adaptive escape of nondormant white oaks. Behav Ecol 21:169–175
Zwolak R, Crone EE (2012) Quantifying the outcome of plant–granivore interactions. Oikos 121:20–27
Acknowledgments
Funding for this work was provided by the Indiana Department of Natural Resources, Division of Fish and Wildlife (State Wildlife Grant T7R12). K. Leffel assisted with seed preference trials. J. McKenna helped procure chestnut seed. N. Lichti, M. Saunders, P. Zollner, and two anonymous reviewers provided helpful comments on the manuscript.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Blythe, R.M., Smyser, T.J. & Swihart, R.K. Tree squirrel seed predation patterns may influence American chestnut restoration success. New Forests 46, 593–600 (2015). https://doi.org/10.1007/s11056-015-9475-7
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11056-015-9475-7