Pseudoreplication and the Design of Ecological Field Experiments

Stuart H. Hurlbert
Ecological Monographs
Vol. 54, No. 2 (Jun., 1984), pp. 187-211
DOI: 10.2307/1942661
Stable URL:
Page Count: 25
  • Download PDF
  • Cite this Item

You are not currently logged in.

Access your personal account or get JSTOR access through your library or other institution:


Log in to your personal account or through your institution.

Pseudoreplication and the Design of Ecological Field Experiments


Pseudoreplication is defined as the use of inferential statistics to test for treatment effects with data from experiments where either treatments are not replicated (though samples may be) or replicates are not statistically independent. In ANOVA terminology, it is the testing for treatment effects with an error term inappropriate to the hypothesis being considered. Scrutiny of 176 experimental studies published between 1960 and the present revealed that pseudoreplication occurred in 27% of them, or 48% of all such studies that applied inferential statistics. The incidence of pseudoreplication is especially high in studies of marine benthos and small mammals. The critical features of controlled experimentation are reviewed. Nondemonic intrusion is defined as the impingement of chance events on an experiment in progress. As a safeguard against both it and preexisting gradients, interspersion of treatments is argued to be an obligatory feature of good design. Especially in small experiments, adequate interspersion can sometimes be assured only by dispensing with strict randomization procedures. Comprehension of this conflict between interspersion and randomization is aided by distinguishing pre-layout (or conventional) and layout-specific alpha (probability of type I error). Suggestions are offered to statisticians and editors of ecological journals as to how ecologists' understanding of experimental design and statistics might be improved.

Notes and References

This item contains 125 references.

Literature Cited
  • Abbott, W.1966. Microcosm studies on estuarine waters. I. The replicability of microcosms. Journal of the Water Polution Control Federation38:258-270.
  • —1967. Microcosm studies on estuarine waters. II. The effects of single doses of nitrate and phosphate. Journal of the Water Polution Control Federation39:113-122.
  • Abramsky, Z., M. I. Dyer, and P. D. Harrison. 1979. Com- petition among small mammals in experimentally per- turbed areas of the shortgrass prarie. Ecology60:530-536.
  • Anscombe, F. J.1948. The validity of comparative exper- iments. Journal of the Royal Statistical Society (London) A111:181-211.
  • Bakelaar, R. G., and E. P. Odum. 1978. Community and population level responses to fertilization in an old-field ecosystem. Ecology59:660-665.
  • Barbacki, S., and R. A. Fisher. 1936. A test of the supposed precision of systematic arrangements. Annals of Eugenics 7:183-193.
  • Barrett, G. W.1968. The effects of an acute insecticide stress on a semi-enclosed grassland ecosystem. Ecology49:1019- 1035.
  • Bell, S. S.1980. Meiofauna-macrofauna interactions in a high salt marsh habitat. Ecological Monographs50:487- 505.
  • Bell, S. S., and B. C. Coull. 1978. Field evidence that shrimp predation regulates meiofauna. Oecologia35:245-248.
  • Beyers, R. J.1963. The metabolism of twelve aquatic lab- oratory microecosystems. Ecological Monographs33:281- 306.
  • Boaden, P. J. S.1962. Colonization of graded sand by an interstitial fauna. Cahiers de Biologie Marine3:245-248.
  • Box, J. F.1978. R. A. Fisher: the life of a scientist. Wiley, New York, New York, USA.
  • Brown, J. H., J. J. Graver, and D. W. Davidson. 1975. A preliminary study of seed predation in desert and montane habitats. Ecology56:987-992.
  • Buzas, M. A.1978. Foraminifera as prey for benthic deposit feeders: results of predator exclusion experiments. Journal of Marine Research36:617-625.
  • Cameron, G. N.1977. Experimental species removal: de- mographic responses by Sigmodolt hispidus and Reithro- dontomysfulvescens. Journal of Mammalogy58:488-506.
  • Chew, R. M.1978. The impact of small mammals on eco- system structure and function. Pages 167-180 in D. P. Sny- der, editor. Populations of small mammals under natural conditions. Pymatuning Symposia in Ecology Number 5, Pymatuning Laboratory of Ecology, University of Pitts- burgh, Pittsburgh, Pennsylvania, USA.
  • Clarke, R. D., and P. R. Grant. 1968. An experimental study of the role of spiders as predators in a forest litter com- munity. Part I. Ecology49:1152-1154.
  • Clark, R. W.1976. The life of Bertrand Russell. Knopf, New York, New York, USA.
  • Cochran, W. G.1963. Sampling techniques. Third edition. Wiley, New York, New York, USA.
  • —1980. Fisher and the analysis of variance. Pages 17- 34 in E. Fienberg and D. V. Hinckley, editors. R. A. Fischer: an appreciation (Lecture Notes in Statistics, Volume 1). Springer-Verlag, New York, New York, USA.
  • Cochran, W. G., and G. M. Cox. 1957. Experimental de- signs. Second edition. Wiley, New York, New York, USA.
  • Connell, J. H.1974. Field experiments in marine ecology. Pages 21-54 in R. Mariscal, editor. Experimental marine biology. Academic Press, New York, New York, USA.
  • Cooke, G. D.1977. Experimental aquatic laboratory eco- systems and communities. Pages 59-103 in J. Cairns, ed- itor. Aquatic microbial communities. Garland, New York, New York, USA.
  • Cope, 0. B., J. P. McCraren, and L. Eller. 1969. Effects of dichlobenil on two fishpond environments. Weed Science 17:158-165.
  • Cowell, B. C.1965. The effects of sodium arsenite and Silvex on the plankton populations in farm ponds. Transactions of the American Fisheries Society94: 371.
  • Cox, D. R.1958. Planning of experiments. Wiley, New York, New York, USA.
  • Cox, P. A. 1981. Vertebrate pollination and the mainte- nance of unisexuality in Freycinetia. Dissertation. Harvard University, Cambridge, Massachusetts, USA.
  • —1982. Vertebrate pollination and the maintenance of dioecism in Freycinetia. American Naturalist120:65- 80.
  • Crowner, A. W., and G. W. Barrett. 1979. Effects of fire on the small mammal component of an experimental grassland community. Journal of Mammalogy60:803-813.
  • Davies, A. G.1978. Pollution studies with marine plankton. Part II. Heavy metals. Advances in Marine Biology15:381- 508.
  • Dobson, F. S.1979. An experimental study of dispersal in the California ground squirrel. Ecology60:1103-1109.
  • Durbin, A. G., S. W. Nixon, and C. A. Oviatt. 1979. Effects of the spawning migration of the alewife, Alosa pseudo- harengus, on freshwater ecosystems. Ecology60:8-17.
  • Eberhardt, L. L.1976. Quantitative ecology and impact assessment. Journal of Environmental Management4:27- 70.
  • —1978. Appraising variability in population studies. Journal of Wildlife Management42:207-238.
  • Fisher, R. A.1926. The arrangement of field experiments. Journal of the Ministry of Agriculture (London)33:503- 513.
  • —1939. "Student." Annals of Eugenics9:1-9.
  • —1958. Statistical methods for research workers. 13th edition. Oliver and Boyd, London, England.
  • —1971. The design of experiments. Ninth edition. Hafner, New York, New York, USA.
  • Fisher, R. A., and W. A. Mackenzie. 1923. Studies in crop variation. II. The manurial response of different potato varieties. Journal of Agricultural Science13:311-320.
  • Fisher, R. A., and J. Wishart. 1930. The arrangement of field experiments and the statistical reduction of the results. Imperial Bureau of Soil Science (London), Technical Com- munication Number10: 1-23.
  • Fry, D. L., and J. A. Osborne. 1980. Zooplankton abun- dance and diversity in central Florida grass carp ponds. Hydrobiologia68:145-155.
  • Gaines, M. S., A. M. Vivas, and C. L. Baker. 1979. An experimental analysis of dispersal in fluctuating vole pop- ulations: demographic parameters. Ecology60:814-828.
  • Gibson, V. R., and G. D. Grice. 1977. Response of macro- zooplankton populations to copper: controlled ecosystem pollution experiment. Bulletin of Marine Science27:85-91.
  • Giesy, J. P., Jr., editor. 1980. Microcosms in ecological research. Technical Information Center, United States De- partment of Energy, Washington, D.C., USA.
  • Giguere, L.1979. An experimental test of Dodson's hy- pothesis that Ambystoma (a salamander) and Chaoborus (a phantom midge) have complementary feeding niches. Ca- nadian Journal of Zoology57:1091-1097.
  • Gilderhus, P. A.1966. Some effects of sublethal concentra- tions of sodium arsenite on bluegills and the aquatic en- vironment. Transactions of the American Fisheries Society 95:289-296.
  • Gossett, W. S.1923. On testing varieties of cereals. Bio- metrika15:271-293.
  • —1936. Cooperation in large scale experiments (a dis- cussion). Journal of the Royal Statistical Society, Supple- ment3:115-136.
  • — ("Student"). 1937. Comparison between balanced and random arrangements of field plots. Biometrika29: 363-379.
  • Grant, W. E., N. R. French, and D. M. Swift. 1977. Response of a small mammal community to water and nitrogen treat- ments in a shortgrass prarie ecosystem. Journal of Mam- malogy58:637-652.
  • Green, R. H.1979. Sampling design and statistical methods for environmental biologists. Wiley, New York, New York, USA.
  • Grice, G. D., M. R. Reeve, P. Koeller, and D. W. Menzel. 1977. The use of large volume, transparent enclosed sea- surface water columns in the study of stress on plankton ecosystems. Helgoländer Wissenschaftliche Meeresunter- suchungen30:118-133.
  • Hall, R. J., G. E. Likens, S. B. Fiance, and G. R. Hendrey. 1980. Experimental acidification of a stream in the Hub- bard Brook Experimental Forest, New Hampshire. Ecology 61:976-989.
  • Hansen, L. P., and G. 0. Batzli. 1979. Influence of supple- mental food on local populations of Peromyscus leucopus. Journal of Mammalogy60:335-342.
  • Harger, J. R. E.1971. Variation and relative "niche" size in the sea mussel Mytilus edulis in association with Mytilus californianus. Veliger14:275-281.
  • Harte, J., D. Levy, J. Rees, and E. Saegebarth. 1980. Making microcosms an effective assessment tool. Pages 105-137 in J. P. Giesy, Jr., editor. Microcosms in ecological research. Technical Information Center, United States Department of Energy, Washington, D.C., USA.
  • Haven, S. B.1973. Competition for food between the in- tertidal gastropods Acmaea scabra and Acmaea digitalis. Ecology54:143-151.
  • Hayne, D. W.1978. Experimental designs and statistical analyses. Pages 3-10 in D. P. Snyder, editor. Populations of small mammals under natural conditions. Pymatuning Symposia in Ecology Number 5. Pymatuning Laboratory of Ecology, University of Pittsburgh, Pittsburgh, Pennsyl- vania, USA.
  • Hayward, G. F., and J. Phillipson. 1979. Community struc- ture and functional role of small mammals in ecosystems. Pages 135-211 in D. M. Stoddart, editor. Ecology of small mammals. Chapman and Hall, London, England.
  • Hixon, M. A.1980. Competitive interactions between Cal- ifornia reef fishes of the genus Embiotoca. Ecology61:918- 931.
  • Holbrook, S. J.1979. Habitat utilization, competitive in- teractions, and coexistence of three species of cricetine ro- dents in east-central Arizona. Ecology60:758-759.
  • Holland, A. F., N. K. Mountfort, M. H. Hiegel, K. R. Kau- meyer, and J. A. Mihursky. 1980. The influence of pre- dation on infaunal abundance in upper Chesapeake Bay. Marine Biology57:221-235.
  • Hurlbert, S. H.1975. Secondary effects of pesticides on aquatic ecosystems. Residue Reviews58:81-148.
  • Hurlbert, S. H., and C. C. Y. Chang. 1983. Ornitholimnol- ogy: effects of grazing by the Andean flamingo (Phoenico- parrus andinus). Proceedings of the National Academy of Sciences (USA)80:4766-4769.
  • Hurlbert, S. H., and M. S. Mulla. 1981. Impacts of mos- quitofish (Gambusia affinis) predation on plankton com- munities. Hydrobiologia83:125-151.
  • Hurlbert, S. H., M. S. Mulla, J. 0. Keith, W. E. Westlake, and M. E. Dusch. 1971. Biological effects and persistence of Dursban in freshwater ponds. Journal of Economic Ento- mology63:43-52.
  • Hurlbert, S. H., M. S. Mulla, and H. R. Willson. 1972. Ef- fects of an organophosphorus insecticide on the phyto- plankton, zooplankton, and insect populations of fresh- water ponds. Ecological Monographs42:269-299.
  • Innis, G. S.1979. Letter to the Editor. Bulletin of the Eco- logical Society of America60:142.
  • Jones, B. R., andJ. B. Moyle. 1963. Populationsofplankton animals and residual chlorinated hydrocarbons in soils of six Minnesota ponds treated for control of mosquito larvae. Transactions of the American Fisheries Society92:211- 219.
  • Joule, J., and G. N. Cameron. 1975. Species removal stud- ies. I. Dispersal strategies of sympatric Sigmodon hispidus and Reithrodontomys fulvescens populations. Journal of Mammalogy56:378-396.
  • Kempthorne, D.1979. The design and analysis of experi- ments. Krieger, Huntington, New York, USA.
  • Kerfoot, W. C., editor. 1980. Evolution and ecology of zoo- plankton communities. (Special Symposium Volume 3, American Society of Limnology and Oceanography) Uni- versity Press of New England, Hanover, New Hampshire, USA.
  • Likens, G. E., F. H. Bormann, N. M. Johnson, D. W. Fisher, and R. S. Pierce. 1970. Effects of forest cutting and her- bicide treatment on nutrient budgets in the Hubbard Brook watershed ecosystem. Ecological Monographs40:23-47.
  • Likens, G. E., F. H. Bormann, R. S. Pierce, J. S. Eaton, and N. M. Johnson. 1977. Biogeochemistry of a forested eco- system. Springer-Verlag, New York, New York, USA.
  • Lubchenco, J.1980. Algal zonation in the New England rocky intertidal community: an experimental analysis. Ecology61:333-344.
  • Maki, A. W.1980. Evaluation oftoxicant effects on structure and function of model stream communities: correlation with natural stream effects. Pages 583-609 in J. P. Giesy, Jr., editor. Microcosms in ecological research. Technical Information Center, United States Department of Energy, Washington, D.C., USA.
  • Malone, C. R.1969. Effects of Diazinon contamination on an old-field ecosystem. American Midland Naturalist82: 1-27.
  • Manuel, C. Y., and G. W. Minshall. 1980. Limitations on the use of microcosms for predicting algal response to nu- trient enrichment in lotic systems. Pages 645-667 in J. P. Giesy, Jr., editor. Microcosms in ecological research. Tech- nical Information Center, United States Department of En- ergy, Washington, D.C., USA.
  • Markowitz, D. V.1980. Predator influence on shore-level size gradients in Tegulafunebralis. Journal of Experimental Marine Biology and Ecology45:1-13.
  • Marshall, J. S., and D. L. Mellinger. 1980. Dynamics of cadmium-stressed plankton communities. Canadian Jour- nal of Fisheries and Aquatic Sciences37:403-414.
  • McCauley, E., and F. Briand. 1979. Zooplankton grazing and phytoplankton species richness: field tests of the pre- dation hypothesis. Limnology and Oceanography24:243- 252.
  • McIntire, C. D.1968. Structural characteristics of benthic algal communities in laboratory streams. Ecology49:520- 537.
  • McIntire, C. D., R. L. Garrison, H. K. Phinney, and C. E. Warren. 1964. Primary production in laboratory streams. Limnology and Oceanography9:92-102.
  • Menge,B.A.1972. Competitionforfoodbetweenintertidal starfish species and its effect on body size and feeding. Ecol- ogy53:635-644.
  • Menzel, D. W.1977. Summary of experimental results: con- trolled ecosystem pollution experiment. Bulletin of Marine Science27:142-145.
  • Menzel, D. W., and J. Case. 1977. Concept and design: controlled ecosystem pollution experiment. Bulletin of Ma- rine Science27:3-7.
  • Munger, J. C., and J. H. Brown. 1981. Competition in desert rodents: an experiment with semipermeable exclosures. Sci- ence211:510-512.
  • Neyman, J., and E. S. Pearson. 1937. Notes on some points in "Student's" paper on "Comparison between balanced and random arrangements of field plots." Biometrika29: 380-388.
  • Paine, R. T.1974. Intertidal community structure: experi- mental studies on the relationship between a dominant competitor and its principal predator. Oecologia15:93- 120.
  • —1980. Food webs, linkage, interaction strength and community infrastructure. Journal of Animal Ecology49: 667-685.
  • Pearson, E. S.1939. William Sealey Gossett, 1876-1937. (2) "Student" as statistician. Biometrika30:210-250.
  • Peterson, C. H.1977. Competitive organization of the soft- bottom macrobethnic communities of southern California lagoons. Marine Biology43:343-359.
  • Price, M.1978. The role of microhabitat in structuring des- ert rodent communities. Ecology59:910-921.
  • Rausher, M. D., and P. Feeny. 1980. Herbivory, plant den- sity, and plant reproductive success: the effect of Battus philenor on Aristolochia reticulata. Ecology61:905-917.
  • Reichman, 0. J.1979. Desert granivore foraging and its impact on seed densities and distributions. Ecology60:1085- 1092.
  • Reise, K.1978. Experiments on epibenthic predation in the Wadden Sea. Helgoländer Wissenschaftliche Meeresunter- suchungen31:55-101.
  • Rodgers, J. H., Jr., J. R. Clark, K. L. Dickson, and J. Cairns, Jr.1980. Nontaxonomic analyses of structure and func- tion of aufwuchs communities in lotic microcosms. Pages 625-644 in J. P. Giesy, Jr., editor. Microcosms in ecological research. Technical Information Center, United States De- partment of Energy, Washington, D.C., USA.
  • Rogers, C. S.1979. The effect of shading on coral reef struc- ture and function. Journal of Experimental Marine Biology and Ecology41:269-288.
  • Savage, L. J., moderator. 1962. The foundations of statis- tical inference: a discussion. Wiley, New York, New York, USA.
  • Schindler, D. W.1974. Eutrophication and recovery in ex- perimental lakes: implications for lake management. Sci- ence184:897-898.
  • Schindler, D. W., F. A. J. Armstrong, S. K. Holmgren, and G. J. Brunskill. 1971. Eutrophication of lake 227, Exper- imental Lakes Area, northwestern Ontario, by addition of phosphate and nitrate. Journal of the Fisheries Research Board of Canada28:1763-1782.
  • Sherman, K. M., and B. C. Coull. 1980. The response of meiofauna to sediment disturbance. Journal of Experimen- tal Marine Biology and Ecology46:59-71.
  • Slocum, C. J.1980. Differential susceptibility to grazers in two phases of an intertidal alga: advantages of heteromor- phic generations. Journal of Experimental Marine Biology and Ecology46:99- 110.
  • Sokal, R. R., and F. J. Rohlf. 1981. Biometry. Second edi- tion. Freeman, San Francisco, California, USA.
  • Spencer, S. R., and G. W. Barrett. 1980. Meadow vole pop- ulation response to vegetational changes resulting from 2, 4-D application, American Midland Naturalist103:32-46.
  • Spitz, F.1968. Interaction entre vegetation epigee d'une luzerniere et des populations enclose ou non enclose de Microtus arvalis Pallas. Terre et Vie1968:274-306.
  • Steel, R. G. D., and J. H. Torrie. 1980. Principles and pro- cedures of statistics. Second edition. McGraw-Hill, New York, New York, USA.
  • Suttman, C. E., and G. W. Barrett. 1979. Effects of Sevin on arthropods in an agricultural and an old-field plant com- munity. Ecology60:628-641.
  • Takahashi, M., W. H. Thomas, D. L. R. Seibert, J. Beers, P. Koeller, and T. R. Parsons. 1975. The replication of bi- ological events in enclosed water columns. Archiv für Hy- drobiologie76:5-23.
  • Thomas, W. H., and D. L. R. Seibert. 1977. Effects of copper on the dominance and diversity of algae: controlled eco- system pollution experiment. Bulletin of Marine Science 27:17-22.
  • Underwood, A. J.1981. Techniques of analysis of variance in experimental marine biology and ecology. Oceanography and Marine Biology Annual Reviews19:513-605.
  • Vance, R. R.1979. Effects of grazing by the sea urchin, Centrostephanus coronatus, on prey community composi- tion. Ecology60:537-546.
  • Vance, R. R., and R. J. Schmitt. 1979. The effect of the predator-avoidance behavior of the sea urchin, Centro- stephanus coronatus, on the breadth of its diet. Oecologia (Berlin)44:21-45.
  • Virnstein, R. W.1977. The importance of predation by crabs and fishes on benthic infauna in Chesapeake Bay. Ecology58:1199-1217.
  • Vossbrinck, C. R., D. C. Coleman, and T. A. Wooley. 1979. Abiotic and biotic factors in litter decomposition in a semi- arid grassland. Ecology60:265-271.
  • Waloff, N., and 0. W. Richards. 1977. The effect of insect fauna on growth mortality and natality of broom, Saro- thamnus scoparius. Journal of Applied Ecology14:787- 798.
  • Warwick, R. M., J. T. Davey, J. M. Gee, and C. L. George. 1982. Faunistic control of Enteromorpha blooms: a field experiment. Journal of Experimental Marine Biology and Ecology56:23-31.
  • Werner, E. E., and D. J. Hall. 1976. Niche shifts in sunfishes: experimental evidence and significance. Science191:404- 406.
  • Whittaker, R. H.1961. Experiments with radiophosphorus tracer in aquarium microcosms. Ecological Monographs31: 157-188.
  • Winer, B. J.1971. Statistical principles in experimental de- sign. McGraw-Hill, New York, New York, USA.
  • Wishart, J.1934. Statistics in agricultural research. Journal of the Royal Statistical Society1:26-61.
  • Yates, F.1939. The comparative advantages of systematic and randomized arrangements in the design of agricultural and biological experiments. Biometrika30:440-466.
  • —1960. Sampling methods for censuses and surveys. Third edition. Hafner, New York, New York, USA.
  • Youden, W. J.1972. Randomization and experimentation. Technometrics14:13-22.
  • Young, D. K., M. A. Buzas, and M. W. Young. 1976. Species densities of macrobenthos associated with seagrass: a field experimental study of predation. Journal of Marine Re- search34:577-592.