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General patterns of taxonomic and biomass partitioning in extant and fossil plant communities


A central goal of evolutionary ecology is to identify the general features maintaining the diversity of species assemblages1,2,3. Understanding the taxonomic and ecological characteristics of ecological communities provides a means to develop and test theories about the processes that regulate species coexistence and diversity. Here, using data from woody plant communities from different biogeographic regions, continents and geologic time periods, we show that the number of higher taxa is a general power-function of species richness that is significantly different from randomized assemblages. In general, we find that local communities are characterized by fewer higher taxa than would be expected by chance. The degree of taxonomic diversity is influenced by modes of dispersal and potential biotic interactions. Further, changes in local diversity are accompanied by regular changes in the partitioning of community biomass between taxa that are also described by a power function. Our results indicate that local and regional processes2 have consistently regulated community diversity and biomass partitioning for millions of years.

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We thank J. H. Brown, S. Collins, R. Colwell, M. J. Donoghue, N. J. Gotelli, D. Post, S. P. Hubbell, C. J. Humphries, W. P. Maddison, K. J. Niklas, N. Pittman, F. A. Smith, M. Weiser, J. Williams, R. Whittaker and the members of the NCEAS Body Size Working Group and Phylogenies and Community Ecology Working Group for critical discussions and/or comments on earlier drafts. In particular, C. O. Webb provided valuable comments. This work stems in part from the Body Size in Ecology and Evolution Working Group (F.A. Smith, Principal Investigator) sponsored by The National Center for Ecological Analysis and Synthesis (NCEAS, a national centre funded by the NSF, the University of California Santa Barbara and the State of California). B.J.E. was supported by the NSF and NCEAS. J.P.H. was supported by a student internship from NCEAS. Computer resources for the simulations were provided by the UNM Department of Biology, Sevilleta Long Term Ecological Research site and NCEAS.

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Correspondence to Brian J. Enquist.

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The authors declare that they have no competing financial interests.

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Table 1 and Discussion, Methods and Analysis (DOC 665 kb)

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Further reading

Figure 1: Three graphical hypotheses for the relationship between species richness and number of higher taxa within a local community.
Figure 2: Relationship between the number of species and higher taxa across 227 0.1-ha sites from around the world.
Figure 3: Relationship between the number of species and higher taxa across 28 local palaeoflora sites ranging from 4.5 to 45 Myr ago.
Figure 4: Relationship between species pool size and the results of randomization experiments using the total number of sampled sites from South America.
Figure 5: Biomass partitioning between species (open squares), genera (open circles), and families (filled diamonds) across global woody plant communities.


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