Density-dependent mortality and the latitudinal gradient in species diversity


Ecologists have long postulated that density-dependent mortality maintains high tree diversity in the tropics1,2,3,4,5,6. If species experience greater mortality when abundant, then more rare species can persist1,2,7,8,9. Agents of density-dependent mortality (such as host-specific predators, and pathogens) may be more prevalent or have stronger effects in tropical forests, because they are not limited by climatic factors1,2,3,4,5. If so, decreasing density-dependent mortality with increasing latitude could partially explain the observed latitudinal gradient in tree diversity4,5,6. This hypothesis has never been tested with latitudinal data. Here we show that several temperate tree species experience density-dependent mortality between seed dispersal and seedling establishment. The proportion of species affected is equivalent to that in tropical forests6,10,11,12,13,14,15,16, failing to support the hypothesis that this mechanism is more prevalent at tropical latitudes. We further show that density-dependent mortality is misinterpreted in previous studies. Our results and evidence from other studies suggest that density-dependent mortality is important in many forests. Thus, unless the strength of density-dependent mortality varies with latitude, this mechanism is not likely to explain the high diversity of tropical forests.

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Figure 1: The observed (a) and predicted (b) relationship between conspecific seed density and seed germination for Acer rubrum.
Figure 2: The proportion of tree taxa experiencing density-dependent mortality at different latitudes.
Figure 3: Five analyses used to test for density-dependent mortality are applied to seed bank incorporation, germination, establishment and over-winter survival.


  1. 1

    Janzen, D. H. Herbivores and the number of tree species in tropical forests. Am. Nat. 104, 501–528 (1970)

    Article  Google Scholar 

  2. 2

    Connell, J. H. in Dynamics of Populations (eds den Boer, P. J. & Gradwell, G. R.) 298–312 (Center for Agricultural Publication and Documentation, Wageningen, The Netherlands, 1971)

    Google Scholar 

  3. 3

    Coley, P. D. & Barone, J. A. Herbivory and plant defenses in tropical forests. Annu. Rev. Ecol. Syst. 27, 305–335 (1996)

    Article  Google Scholar 

  4. 4

    Givnish, T. J. On the causes of gradients in tropical tree diversity. J. Ecol. 87, 193–210 (1999)

    Article  Google Scholar 

  5. 5

    Leigh, E. G. Tropical Forest Ecology 190–195 (Oxford University Press, New York, 1999)

    Google Scholar 

  6. 6

    Harms, K. E., Wright, S. J., Calderon, O., Hernandez, A. & Herre, E. A. Pervasive density-dependent recruitment enhances seedling diversity in a tropical forest. Nature 404, 493–495 (2000)

    ADS  CAS  Article  Google Scholar 

  7. 7

    Howe, H. F. & Smallwood, J. Ecology of seed dispersal. Annu. Rev. Ecol. Syst. 13, 201–228 (1982)

    Article  Google Scholar 

  8. 8

    Becker, P., Lee, L. W., Rotham, E. D. & Hamilton, W. D. Seed predation and the coexistence of tree species: Hubbell's models revisited. Oikos 44, 382–390 (1985)

    Article  Google Scholar 

  9. 9

    Pacala, S. W. & Crawley, M. J. Herbivores and plant diversity. Am. Nat. 140, 243–260 (1992)

    CAS  Article  Google Scholar 

  10. 10

    Connell, J. H., Tracey, J. G. & Webb, L. J. Compensatory recruitment, growth, and mortality as factors maintaining rain forest tree diversity. Ecol. Monogr. 54, 141–164 (1984)

    Article  Google Scholar 

  11. 11

    Condit, R., Hubbell, S. P. & Foster, R. B. Recruitment near conspecific adults and the maintenance of tree and shrub diversity in a neotropical forest. Am. Nat. 140, 261–286 (1992)

    CAS  Article  Google Scholar 

  12. 12

    Okuda, T., Kachi, N., Yap, S. K. & Manokaran, N. Tree distribution pattern and fate of juveniles in a lowland tropical rain forest—implications for regeneration and maintenance of species diversity. Plant Ecol. 131, 155–171 (1997)

    Article  Google Scholar 

  13. 13

    Wills, C. & Condit, R. Similar non-random processes maintain diversity in two tropical rainforests. Proc. R. Soc. Lond. B 266, 1445–1452 (1999)

    CAS  Article  Google Scholar 

  14. 14

    Penfold, G. C. & Lamb, D. Species co-existence in an Australian subtropical rain forest: evidence for compensatory mortality. J. Ecol. 87, 316–329 (1999)

    Article  Google Scholar 

  15. 15

    Webb, C. O. & Peart, D. R. Seedling density dependence promotes coexistence of Bornean rain forest trees. Ecology 80, 2006–2017 (1999)

    Article  Google Scholar 

  16. 16

    Wills, C., Condit, R., Foster, R. B. & Hubbell, S. P. Strong density- and diversity-related effects help to maintain tree species diversity in a neotropical forest. Proc. Natl Acad. Sci. USA 94, 1252–1257 (1997)

    ADS  CAS  Article  Google Scholar 

  17. 17

    Augsburger, C. K. Seedling survival of tropical tree species: interactions of dispersal distance, light gaps, and pathogens. Ecology 65, 1705–1712 (1984)

    Article  Google Scholar 

  18. 18

    Gilbert, G. S., Hubbell, S. P. & Foster, R. B. Density and distance to adult effects of a canker disease of trees in moist tropical forest. Oecologia 98, 100–108 (1994)

    ADS  CAS  Article  Google Scholar 

  19. 19

    Cintra, R. A test of the Janzen–Connell model with two common tree species in Amazonian forest. J. Trop. Ecol. 8, 529–536 (1997)

    Google Scholar 

  20. 20

    Carson, W. P. & Root, R. R. Herbivory and plant species coexistence: community regulation by an outbreaking phytophagous insect. Ecol. Monogr. 70, 73–99 (2000)

    Article  Google Scholar 

  21. 21

    Packer, A. & Clay, K. Soil pathogens and spatial patterns of seedling mortality in a temperate tree. Nature 404, 278–281 (2000)

    ADS  CAS  Article  Google Scholar 

  22. 22

    Streng, D. R., Glitzenstein, J. S. & Harcombe, P. A. Woody seedling dynamics in an east Texas floodplain forest. Ecol. Monogr. 59, 177–204 (1989)

    Article  Google Scholar 

  23. 23

    Jones, R. H., Sharitz, R. R., Dixon, P. M., Segal, D. S. & Schneider, R. L. Woody plant regeneration in four floodplain forests. Ecol. Monogr. 64, 345–367 (1994)

    Article  Google Scholar 

  24. 24

    Connell, J. H. Diversity in tropical rain forests and coral reefs. Science 199, 1302–1310 (1978)

    ADS  CAS  Article  Google Scholar 

  25. 25

    Hubbell, S. P. Seed predation and the coexistence of tree species in tropical forests. Oikos 35, 214–229 (1980)

    Article  Google Scholar 

  26. 26

    McCanny, S. J. Alternatives in parent–offspring relationships in plants. Oikos 45, 148–149 (1985)

    Article  Google Scholar 

  27. 27

    Hubbell, S. P., Condit, R. & Foster, R. B. Presence and absence of density dependence in a neotropical tree community. Phil. Trans. R. Soc. Lond. B 330, 269–281 (1990)

    ADS  Article  Google Scholar 

  28. 28

    Schupp, E. W. The Janzen–Connell model for tropical tree diversity: population implications and the importance of spatial scale. Am. Nat. 140, 526–530 (1992)

    CAS  Article  Google Scholar 

  29. 29

    Clark, D. A. & Clark, D. B. Spacing dynamics of a tropical rain forest tree: evaluation of the Janzen–Connell model. Am. Nat. 124, 769–788 (1984)

    Article  Google Scholar 

  30. 30

    Clark, J. S., Macklin, E. & Wood, L. Stages and spatial scales of recruitment limitation in southern Appalachian forests. Ecol. Monogr. 68, 213–235 (1998)

    Article  Google Scholar 

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Funding was provided by Sigma Xi and National Science Foundation grants. We thank M. Dietze, K. Harms, I. Ibanez, S. Ladeau, J. Lynch, J. McLachlan, J. Mohan, A. Pringle and M. Rocca for discussion of data and comments on drafts of the manuscript. Support in the field was provided by R. Hille Ris Lambers and H. Passmore.

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Hille Ris Lambers, J., Clark, J. & Beckage, B. Density-dependent mortality and the latitudinal gradient in species diversity. Nature 417, 732–735 (2002).

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