Outline Community Ecology Indirect effects Keystone species Invasive

Outline • Community Ecology – – Indirect effects, Keystone species, Invasive species Biodiversity: importance and evaluation The new paradigm in ecology: communities in flux Conservation of species interactions • Ecosystem Ecology – Ecosystem services – Biodiversity and ecosystem services – Ecosystems of special concern (Marine and Tropical)

Successful Biological Control

Is Biodiversity Important? • Conservation Biology Perspective – Inherently valuable • Utilitarian Perspective – Natural resources: Genetic libraries; natural design • Ecological Role – Invasibility – Stability – Ecosystem Function

Diversity and Invasibility • Tilman, D. 1997. Community invasibility, recruitment limitation, and grassland biodiversity. Ecology 78: 81 -92. – Seeds from up to 54 plant species (native but mostly rare) were added to patches of native grassland – The % seeds established was negatively correlated with species diversity • Conclusion: Invasibility may decrease with biodiversity

Diversity and Stability • • • Year to year variability in species abundance higher in species rich plots Year to year variability in total biomass lower in species rich plots Effect of drought lower in spp. rich plots Tilman, D. 1996. Biodiversity: Population versus ecosystem stability. Ecology 77: 350 -363.

Diversity and Stability • Hypothetical Mechanism: When climatic variations harm some spp. , unharmed spp. increase. This compensatory increases stabilize ecosystem processes (i. e. productivity) but cause populations to be more variable • This was apparent for both EV (non-drought years) and “catastrophes” (drought years)

What is “Stability” • Historical – Constancy of ecological communities • Modern – Resilience • Operational – Variation in community or ecosystem processes

Tentative Conclusions • At the community level, species diversity may. . . – Increase stability (reduce invasibility) – Decrease stability (year-to-year variation in population abundance)

The “New” Paradigm in Ecology • Clements, F. E. 1936. Nature and structure of the climax. Journal of Ecology 24: 252284. – Climax succession • Gleason, H. A. 1926. The individualistic concept of the plant association. Bulletin of the Torrey Botanical Club 53: 7 -26. – “Random” succession

The Land Ethic and Stability • "A thing is right when it tends to preserve the integrity, stability, and beauty of the biotic community. It is wrong when it does otherwise. " - Aldo Leopold

Number of species Intermediate Disturbance Hypothesis Disturbance rate

Community Ecology and Conservation classical paradigm contemporary paradigm Natural systems closed open, subject to change by natural/human events Stable states 1 more than 1 Metaphor balance of nature flux of nature Conservation implication any natural unit is conservable; keep humans out manage process and context, not species; humans included

Community Ecology and Conservation: Nested Communities

Community Ecology and Conservation: Nested Communities 17 2 10 14 6 7 11 9 12 18 3 13 16 19 15 1 5 8 4 Eu Ed Ml Mf Sp Op Sb x x x x x x x x x x x x x xx x x x x