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Spatial scaling, metacommunity structure, and patterns in stream communities

Topic and aims of the project

Community ecology has been experiencing a paradigm shift in the last decade. This shift has materialised in explicit interest in both local and regional processes in the context of metacommunities. A metacommunity can be defined as a set of local communities connected by the dispersal of constituent species. Metacommunities of stream organisms have been considered in a relatively few studies, and broad generalisations are not yet possible. However, recent findings suggest that both local environmental conditions and dispersal jointly determine structuring of stream metacommunities. The relative importance of local and regional processes may be contingent on the dispersal abilities of studied groups, with strong dispersers showing less spatial structure (i.e. dispersal limitation) and more environment-related structure (i.e. species sorting) than weak dispersers. The relative roles of spatial and environmental control of community structure will be examined in this project for a number of stream organism groups differing in dispersal characteristics and other biological traits. Thus, do organism groups differing in biological characteristics differ in the structuring of a metacommunity?

An important part of studies in metacommunity ecology relates to the effects of spatial scaling. Thus, are patterns in community structure similar across the studied spatial scales? In this respect, three aspects of stream macroinvertebrate communities across scales will be examined. First, the relationship between local species richness (LSR) and regional species richness (RSR) will be studied based on a number differing combinations of local arenas and regional species pools from each of 10 riffle sites in each of 10 streams in a boreal drainage basin. It can be hypothesised that when LSR is based on small scale samples (20 × 20 cm plots) and RSR is based on riffle site pooled sample, the relationship is asymptotic. This reflects the constraining role of interspecific interactions at small scales. By contrast, the LSR-RSR relationships should be linear when LSR is based on pooled riffle scale samples and RSR is based on pooled samples from each stream. This mirrors the constraining role of among-stream dispersal limitation in affecting macroinvertebrate diversity.

Second, the issue of spatial scaling will be considered in comparisons of stream macroinvertebrate communities within and between streams. Despite the intuitive appeal to understand the relative variation in community structure between riffles within a stream and between streams, very few studies have examined variability among these scales. This is surprising given the importance to understand the degree to which a single riffle site represents a stream in both basic and applied stream research. For example, if riffle sites within a stream differ considerably in physical conditions and thereby macroinvertebrate communities, then the relationships of macroinvertebrate communities to stream water chemistry based on a single riffle site may be misleading.

Third, nestedness of stream macroinvertebrates will be studied at the within- and between-streams scales. A perfectly nested pattern occurs when low-richness communities comprise proper subsets of species in high-richness communities. Despite that significant nestedness has been found in stream macroinvertebrates, its degree has typically been rather low. Low degree of nestedness is likely to result from idiosyncratic distributions of many species, as well as the fact that studies range across different stream types. Idiosyncratic species and the effects of changing stream type on nestedness will be studied within and across streams in boreal drainage basins. Thus, are there more idiosyncratic species and lower degree of nestedness in across- than within-streams analyses? This question is related to fact that within-stream analyses comprise a single habitat type, while across-stream analyses may range across different habitat types.

The results of this project should increase our understanding of metacommunity structuring and spatial scaling in stream systems. The project will entail both international and national collaboration due to the importance to apply sophisticated statistical methods and knowledge on multiple organism groups.

The aim of this project is to examine general ecological phenomena with stream organisms and communities as model systems. The primary study topics are to examine:

  •  factors determining metacommunity structure at various spatial scales,
  • the relative roles of local environmental factors and spatial location in affecting algal, bryophyte, and macroinvertebrate community structure in streams, and 
  • the relationships between local and regional species richness at multiple spatial scales. 

Although the project is mainly concerned with basic ecological issues, there will be several applications of the research in the applied fields of conservation biology and environmental assessment.

Implementation of the project

The project will begin on 1st August 2009 and it will end on 31st July 2014. The contents and structure of the project have been mostly planned already, but some details will be changed with the advancement of the research. The research began through field sampling already in 2008, and field sampling was continued in 2009 and 2010. The project will lead to at least one PhD thesis and several other theses.

Recent papers published during the project

  • Heino, J. 2009. Species co-occurrence, nestedness and guild-environment relationships in stream macroinvertebrates. Freshwater Biology 54: 1947-1959.
  • Heino, J., Bini, L.M., Karjalainen, S.M., Mykrä, H., Soininen, J., Vieira, L.C.G. & Diniz-Filho, J.A.F. 2010. Geographical patterns of micro-organismal community structure: are diatoms ubiquitously distributed across boreal streams? Oikos 119: 129-137.
  • Heino, J. & Soininen, J. 2010. Are common species sufficient in describing turnover in aquatic metacommunities along environmental and spatial gradients? Limnology and Oceanography 55: 2397-2402.
  • Heino, J., Mykrä, H. & Rintala, J. 2010. Assessing patterns of nestedness in stream insect assemblages along environmental gradients. Ecoscience 17: 345-355.
  • Astorga, A., Heino, J., Luoto, M. & Muotka, T. 2010. Freshwater biodiversity at a regional scale: determinants of macroinvertebrate taxonomic richness in boreal streams. Ecography, in press.
  • Heino, J. 2011. A macroecological perspective of diversity patterns in the freshwater realm. Freshwater Biology, in press.

Further information

One to two students will be considered for conducting their thesis work in the project each year. Students interested in doing their theses in the project should contact the project leader.

  • Academy Research Fellow Dr. Jani Heino, Finnish Environment Institute, firstname.lastname@ymparisto.fi

Published 2013-04-16 at 14:15, updated 2013-04-16 at 14:11