Biological Diversity in the Tropics: What's the Latest Scoop? (Draft #1)

This discussion topic submitted by Susan Lamont ( on 4/28/98.

I. Tropical Forests - how diverse are they?

II. Geologic history of tropical regions

III. evolution in tropical environments
A. "advantages" to growth
1. absence of seasonally low temperatures
2. prolonged growing season
B. "constraints" to growth
1. low soil nutrients
2. persistent biological interactions (predation, herbivory)

IV. Hypotheses explaining tropical biological diversity
A. Janzen-Connell hypothesis
B. intermediate disturbance hypothesis - Connell (1978)
C. low soil fertility - Huston (1979)
D. Hubbell-Foster (1986)
E. refugia theory - Simpson and Haffer (1978)
F. soil variability - Gentry (1986)
G. area-dependent speciation - Terborgh (1973), Rosenweig (1995)

V. Critiques of hypotheses - the latest scoop

Connell, J.H. 1971. On the role of natural enemies in preventing competitive exclusion in some marine animals and rain forest trees. In Dynamics of populations (ed. P.J. den Boer and G.R. Gradwell). Wagenigen, the Netherlands: Center for Agricultural Publishing and Documentation, 298-310.
Connell, J.H. 1978. Diversity in tropical rain forests and coral reefs. Science 199: 1302-1310.
Gentry, A.H. 1986. Endemism in tropical versus temperate plant communities. In Conservation biology: the science of scarcity and diversity (ed. M.E. Soule). sunderland, MA: Sinauer, 153-181.
Gentry, A.H. 1988. Changes in plant community diversity and floristic composition on environmental and geographic gradients. Annals of the Missouri Botanical Garden 75: 1-34.
Hubbell, S.P. and R.B. Foster. 1986. Biology, chance and history and the structure of tropical rain forest tree communities. In Community ecology (ed. J. Diamond and T.J. Chase). New York: Harper and Row, 314-329.
Huston, M.A. 1979. A general hypothesis of species diversity. American Naturalist 113: 81-101.
Huston, M.A. 1980. Soil nutrients and tree species richness in Costa Rican forests. Journal of Biogeography 7: 147-157.
Janzen, D.H. 1970. Herbivores and the number of tree species in tropical forests. American Naturalist 104: 501-528.
Ricklefs, R.E. 1987. Community diversity: relative roles of local and regional processes. Science 235: 161-171.
Ricklefs, R.E. and D. Schluter (eds) 1993. Species diversity in ecological communities: historical and geographical perspectives. Chicago: University of Chicago Press.
Simpson, B. and J. Haffer. 1978. Speciation patterns in the Amazon forest biota. Annual Review of Ecology and Systematics 9: 497-518.
Terborgh, J. 1973. On the notion of favourableness in plant ecology. American Naturalist 107: 481-501.
Terborgh, J. 1992. Maintenance of diversity in tropical forests. Biotropica 24: 283-292.

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