Temporal and spatial concordance in community composition of phytoplankton, zooplankton, macroinvertebrate, crayfish, and fish on the Precambrian Shield 1 Michelle F. Bowman, Ron Ingram, Ron A. Reid, Keith M. Somers, Norman D. Yan, Andrew M. Paterson, George E. Morgan, and John M. Gunn Abstract: Concordance among communities dictates how broadly we can extrapolate results derived from a set of eco- systems. We used Mantel tests to evaluate the degree of concordance in community composition among phytoplankton, zooplankton, benthic macroinvertebrate, crayfish, and fish in eight lakes near Dorset, Ontario, Canada. Spatial concor- dance across lakes at the decadal scale was stronger (mean Mantel r = 0.51, standard deviation (SD) = 0.20) than both intra-annual agreement (mean Mantel r = 0.38, SD = 0.20) and temporal concordance within a single lake (mean Man- tel r = 0.20, SD = 0.15). The degree of temporal concordance was not related to climatic fluctuations, with the excep- tion of increased spatial synchrony in phytoplankton communities in 1997. Strength of overall spatial concordance was most commonly related to variability in chemical attributes of the study lakes. An understanding of the determinants of concordance among taxon groups is germane to the advancement of ecology in general, as well as biodiversity conser- vation strategies, ecosystem monitoring, and impact diagnosis. Résumé : La concordance entre les communautés détermine dans quelle mesure on peut extrapoler les résultats obte- nus dans un ensemble d’écosystèmes. Nous utilisons des tests de Mantel pour évaluer l’importance de la concordance dans la composition de peuplements de phytoplancton, de zooplancton, de macroinvertébrés benthiques, d’écrevisses et de poissons dans huit lacs près de Dorset, Ontario, Canada. La concordance spatiale entre les lacs à l’échelle des décennies est plus forte (r moyen de Mantel = 0,51; écart type (SD) = 0,20) qu’à la fois l’accord entre les années (r moyen de Mantel = 0,38; SD = 0,20) et la concordance temporelle au sein d’un même lac (r moyen de Mantel = 0,20; SD = 0,15). L’importance de la concordance temporelle n’est pas reliée aux fluctuations climatiques, à l’exception d’un synchronisme spatial accru dans les communautés de phytoplancton en 1997. La force de la concor- dance spatiale globale est le plus souvent reliée à la variabilité des caractéristiques chimiques des lacs étudiés. La compréhension des facteurs déterminants de la concordance entre les groupes de taxons est d’intérêt pour le progrès de l’écologie en général, de même que pour les stratégies de conservation de la biodiversité, pour la surveillance des écosystèmes et pour l’identification des impacts. [Traduit par la Rédaction] Bowman et al. 932 Introduction Concordance between taxonomic groups (e.g., plankton and fish) refers to agreement in the relative similarity of community attributes (e.g., richness, composition) over time or space. For example, if the taxonomic richness of both plankton and fish were relatively low at time a, high at time b, and intermediate at time c, the responses of the two groups would be considered temporally concordant. Concor- dant patterns in species distributions among taxon groups can result from common preferences and adaptations, biotic interactions, common environmental determinants, covariance of different environmental determinants, or historical factors (Heino 2002). Although concordance of species richness Can. J. Fish. Aquat. Sci. 65: 919–932 (2008) doi:10.1139/F08-034 © 2008 NRC Canada 919 Received 2 June 2007. Accepted 29 January 2008. Published on the NRC Research Press Web site at cjfas.nrc.ca on 17 April 2008. J20033 M.F. Bowman. 2,3 Department of Zoology, University of Toronto, 25 Harbord Street, Toronto, ON M5S 3G5, Canada. R. Ingram, R.A. Reid, K.M. Somers, and A.M. Paterson. Dorset Environmental Science Centre, Ontario Ministry of the Environment, 1026 Bellwood Acres Road, Dorset, ON P0A 1E0, Canada. N.D. Yan. Department of Biology, York University, 4700 Keele Street, Toronto, ON M3J 1P3, Canada. G.E. Morgan and J.M. Gunn. Cooperative Freshwater Ecology Unit, Department of Biology, Laurentian University, 1222 Ramsey Lake Road, Sudbury, ON P3E 2C6, Canada. 1 This article is part of the series “Transforming understanding of factors that regulate aquatic ecosystems on the southern Canadian Shield”. 2 Corresponding author (e-mail: michelle.f.bowman@gmail.com). 3 Present address: Toxicology Centre, University of Saskatchewan, 44 Campus Drive, Saskatoon, SK S7N 5B3, Canada.