Logic of experiments in ecology: is pseudoreplication a pseudoissue?

Hurlbert divides experimental ecologist into ‘those who do not see any need for dispersion (of replicated treatments and controls), and those who do recognize its importance and take whatever measures are necessary to achieve a good dose of it’. Experimental ecologists could also be divided into those who do not see any problems with sacrificing spatial and temporal scales in order to obtain replication, and those who understand that appropriate scale must always have priority over replication. If an experiment is conducted in a spatial or temporal scale, where the predictions of contesting hypotheses are convergent or ambiguous, no amount of technical impeccability can make the work instructive. Conversely, replication can always be obtained afterwards, by conducting more experiments with basically similar design in different areas and by using meta-analysis. This approach even reduces the sampling bias obtained if resources are allocated to a small number of well-replicated experiments. For a strict advocate of the hypothetico-deductive method, replication is unnecessary even as a matter of principle, unless the predicted response is so weak that random background noise is a plausible excuse for a discrepancy between predictions and results. By definition, a prediction is an ‘all-statement’, referring to all systems within a well-defined category. What applies to all must apply to any. Hence, choosing two systems and assigning them randomly to a treatment and a control is normally an adequate design for a deductive experiment. The strength of such experiments depends on the firmness of the predictions and their a priori probability of corroboration. Replication is but one of many ways of reducing this probability. Whether the experiment is replicated or not, inferential statistics should always be used, to enable the reader to judge how well the apparent patterns in samples reflect real patterns in statistical populations. The concept ‘pseudoreplication’ amounts to entirely unwarranted stigmatization of a reasonable way to test predictions referring to large-scale systems.

[1]  D. McCullough,et al.  Wildlife 2001: Populations , 1996 .

[2]  T. Broadbent,et al.  Criticism and the Growth of Knowledge , 1972 .

[3]  J. Connell.  The Influence of Interspecific Competition and Other Factors on the Distribution of the Barnacle Chthamalus Stellatus , 1961 .

[4]  Erkki Korpimäki,et al.  Experimental reduction of predators reverses the crash phase of small-rodent cycles , 1998 .

[5]  M. Rosenzweig.  Paradox of Enrichment: Destabilization of Exploitation Ecosystems in Ecological Time , 1971, Science.

[6]  Jane Lubchenco,et al.  Algal Zonation in the New England Rocky Intertidal Community: An Experimental Analysis , 1980 .

[7]  T. Klemola,et al.  Do delayed effects of overgrazing explain population cycles in voles , 2000 .

[8]  L. Oksanen.  A century of community ecology: How much progress? , 1991, Trends in ecology & evolution.

[9]  R. Paine.  Food Web Complexity and Species Diversity , 1966, The American Naturalist.

[10]  John H. Lawton,et al.  The Ecotron Facility at Silwood Park: The Value of "Big Bottle" Experiments , 1996 .

[11]  C. Krebs,et al.  What Drives the Snowshoe Hare Cycle in Canada’s Yukon? , 1992 .

[12]  T. Klemola,et al.  Experimental tests of predation and food hypotheses for population cycles of voles , 2000, Proceedings of the Royal Society of London. Series B: Biological Sciences.

[13]  P. J. Hughesdon,et al.  The Struggle for Existence , 1927, Nature.

[14]  L. Oksanen,et al.  Are lemmings prey or predators? , 2000, Nature.

[15]  Peter A. Abrams,et al.  Effect of Increased Productivity on the Abundances of Trophic Levels , 1993, The American Naturalist.

[16]  Joseph H. Connell,et al.  Effects of Competition, Predation by Thais lapillus, and Other Factors on Natural Populations of the Barnacle Balanus balanoides , 1961 .

[17]  T. Paine.  Experimental Studies on the Relationship between a Dominant Competitor and Its Principal Predator , 1974 .

[18]  Tarja Oksanen,et al.  The Logic and Realism of the Hypothesis of Exploitation Ecosystems , 2000, The American Naturalist.

[19]  Stephen R. Carpenter,et al.  Replication and Treatment Strength in Whole‐Lake Experiments , 1989 .

[20]  D. Schluter,et al.  MICROCOSM EXPERIMENTS HAVE LIMITED RELEVANCE FOR COMMUNITY AND ECOSYSTEM ECOLOGY , 1996 .

[21]  Lauri Oksanen,et al.  Grazing by Food-Limited Microtine Rodents on a Productive Experimental Plant Community: Does the "Green Desert" Exist? , 1993 .

[22]  M. Begon,et al.  Ecology: Individuals, Populations and Communities , 1986 .

[23]  Stephen R. Carpenter,et al.  MICROCOSM EXPERIMENTS HAVE LIMITED RELEVANCE FOR COMMUNITY AND ECOSYSTEM ECOLOGY: REPLY , 1999 .

[24]  Peter J. Morin,et al.  Productivity controls food-chain properties in microbial communities , 1998, Nature.

[25]  J. Farris.  CONJECTURES AND REFUTATIONS , 1995, Cladistics : the international journal of the Willi Hennig Society.

[26]  M. Power.  Field biology, food web models, and management: challenges of context and scale , 2001 .

[27]  P. Turchin.  [Does population ecology have general laws?]. , 2001, Zhurnal obshchei biologii.

[28]  L. Oksanen,et al.  Predation and the dynamics of the bank vole, Clethrionomys glareolus , 2000 .

[29]  H. Gleason,et al.  The individualistic concept of the plant association , 1939 .

[30]  G. Huxel,et al.  Microcosms as models for generating and testing community theory , 1996 .

[31]  Edmund Taylor Whittaker,et al.  The Philosophy of Bertrand Russell , 1945, Nature.

[32]  J. Sayers.  Against Method , 2016 .

[33]  S. Pickett,et al.  Ecology: Individuals, populations and communities , 1987 .

[34]  G. Polis,et al.  Food Web Complexity and Community Dynamics , 1996, The American Naturalist.

[35]  I. Lakatos,et al.  The problem of inductive logic , 1970 .

[36]  R. Whittaker.  Communities and Ecosystems , 1975 .

[37]  L. Oksanen,et al.  Exploitation Ecosystems in Gradients of Primary Productivity , 1981, The American Naturalist.

[38]  A. Cajander,et al.  Theory of forest types , 1926 .

[39]  S. Hurlbert.  Pseudoreplication and the Design of Ecological Field Experiments , 1984 .

[40]  De Volson Wood,et al.  Reply to "Criticisms" , 1881 .

[41]  T. Kuhn,et al.  The Structure of Scientific Revolutions , 1963 .

[42]  J. Arthur Thomson,et al.  The aim or science. , 1911 .

[43]  C. Krebs,et al.  Limitation of collared lemming population growth at low densities by predation mortality , 1995 .

[44]  B. Menge,et al.  Competition for Food between Two Intertidal Starfish Species and its Effect on Body Size and Feeding , 1972 .

[45]  C. Krebs,et al.  Microtus Population Biology: Demographic Changes in Fluctuating Populations of M. Ochrogaster and M. Pennsylvanicus in Southern Indiana , 1969 .

[46]  M. Eger.  REPLY TO CRITICISMS , 1988 .

[47]  A. Ives,et al.  Bottle or big-scale studies: how do we do ecology? , 1996 .

[48]  A. J. Underwood,et al.  Experiments in Ecology: Their Logical Design and Interpretation Using Analysis of Variance , 1997 .

[49]  G. O. Batzli,et al.  EFFECTS OF FOOD AVAILABILITY AND PREDATION ON PRAIRIE VOLE DEMOGRAPHY: A FIELD EXPERIMENT' , 1989 .

[50]  J. Andersson,et al.  Interactions among size-structured populations in a whole-lake experiment: size- and scale-dependent processes , 1999 .

[51]  L. Hansson,et al.  Bank vole biology: recent advances in the population biology of a model species , 2000 .

[52]  T. Kuhn.  The structure of scientific revolutions, 3rd ed. , 1996 .

[53]  A. J. Underwood,et al.  Experiments in Ecology. , 1997 .

[54]  Donald R. Strong,et al.  ARE TROPHIC CASCADES ALL WET? DIFFERENTIATION AND DONOR-CONTROL IN SPECIOSE ECOSYSTEMS' , 1992 .

[55]  V. Brown,et al.  Multitrophic Interactions in Terrestrial Systems , 1997 .

[56]  K. Popper.  Logik der Forschung : zur erkenntnistheorie der modernen naturwissenschaft , 1936 .

[57]  R. Paine.  Food webs : linkage, interaction strength and community infrastructure , 1980 .

[58]  I. Lakatos.  Changes in the Problem of Inductive Logic , 1968 .

[59]  Peter A. Abrams,et al.  Predators that Benefit Prey and Prey that Harm Predators: Unusual Effects of Interacting Foraging Adaptation , 1992, The American Naturalist.

[60]  I. Lakatos.  Falsification and the Methodology of Scientific Research Programmes , 1976 .

[61]  S. Erlinge.  Predation and noncyclicity in a microtine population in southern Sweden , 1987 .

[62]  T Seldal,et al.  Grazing-induced proteinase inhibitors: a possible cause for lemming population cycles , 1994 .

[63]  R. Ostfeld.  The fence effect reconsidered , 1994 .

[64]  James R. Bence,et al.  Assessing Effects of Unreplicated Perturbations: No Simple Solutions , 1992 .

[65]  R. Holt.  Population dynamics in two-patch environments: Some anomalous consequences of an optimal habitat distribution , 1985 .

[66]  D. Currie.  Energy and Large-Scale Patterns of Animal- and Plant-Species Richness , 1991, The American Naturalist.

[67]  M. Hunter,et al.  Playing Chutes and Ladders: Heterogeneity and the Relative Roles of Bottom‐Up and Top‐Down Forces in Natural Communities , 1992, Ecology.

[68]  M. Power,et al.  Effects of Fish in River Food Webs , 1990, Science.

[69]  S. Naeem,et al.  CONSUMER SPECIES RICHNESS AND AUTOTROPHIC BIOMASS , 1998 .

[70]  G. Polis,et al.  Why Are Parts of the World Green? Multiple Factors Control Productivity and the Distribution of Biomass , 1999 .

[71]  L. Oksanen.  Predation, herbivory, and plant strategies along gradients of primary productivity. , 1990 .

[72]  K. Popper.  Ein Kriterium des empirifchen Charakters theoretifcher Syfteme , 1932 .

[73]  David F. Rhoades,et al.  Offensive-Defensive Interactions between Herbivores and Plants: Their Relevance in Herbivore Population Dynamics and Ecological Theory , 1985, The American Naturalist.

[74]  Can You Bottle Nature? The Roles of Microcosms in Ecological Research , 1996 .

[75]  L. Oksanen,et al.  Outlines of food webs in a low arctic tundra landscape in relation to three theories on trophic dynamics , 1997 .