Presentation on theme: "Joseph H. Connell Presenter: David Reeves Photo taken by Peter Green."— Presentation transcript:
Joseph H. Connell Presenter: David Reeves Photo taken by Peter Green
Choosing Connell Eight publications with over 1,000 citations Twenty-Nine publications with over 100 citations Wonderful writing style
The Downside? Four publications already covered in this class: Connell JH The Influence of Interspecific Competition and Other Factors on the Distribution of the Barnacle Chthamalus Stellatus. Ecology 42: 710–723. Connell JH Diversity in Tropical Rain Forests and Coral Reefs. Science 199: 1302–1310. Connell JH On the Prevalence and Relative Importance of Interspecific Competition: Evidence from Field Experiments. The American Naturalist 122: 661–696. Connell JH Diversity and the Coevolution of Competitors, or the Ghost of Competition Past. Oikos 35: 131–138. Extremely difficult to find biographical information
Biographical Information (What I know) Born in October 5, 1923 PhD at the University of Glasgow during the 1950’s Produced the famous barnacle study Guggenheim Fellow Eminent Ecologist Award from the ESA Professor Emeritus at UCSB His work was the subject of a symposium at the ESA annual meeting in 2010 (Organized by Dr. Harms)
Today’s Talk Connell JH, Orias E The Ecological Regulation of Species Diversity. The American Naturalist 98: 399– Citations Connell JH Community Interactions on Marine Rocky Intertidal Shores. Annual Review of Ecology and Systematics 3: 169– Citations Connell JH, Slatyer RO Mechanisms of Succession in Natural Communities and Their Role in Community Stability and Organization. The American Naturalist 111: 1119– ,251 Citations
“The Ecological Regulation of Species Diversity”
The Issues: Issue 1 Previous theory has focused on the niche. The greater the number of niches, or niche partitioning, the greater the number of species. However, we cannot account for the number of species in the world with this model. Furthermore, areas with little physical diversification, rainforests and the ocean floor, support an extraordinary number of species.
The Issues: Issue 2 Environmental rigor was being used as a way for explaining diversity and community maturity. Temperate and polar regions are immature because they are environmentally more extreme. However, geological record does not support this idea.
Connell’s Hypothesis In nature, there are climatic variations but organismal fluctuation is typically regulated. This implies that organisms can live with fewer costs for maintenance in an environmentally stable area. In these regions, less energy is spent on maintenance and more is spent on production. Greater population sizes will result because larger animals produce more offspring. Therefore, the diversity in a community is dependent on the amount of energy flowing through the food chain.
The Model There is positive feedback in the model- more stable environment produces more species and larger populations. In early stages there is faster nutrient cycling, increased community stability, and damped climatic fluctuations. In later stages there is overspecialization. There is also negative feedback- overspecialization and decreased stability
The Model: Conclusions This model only applies to equilibrium conditions The idea that the poles and temperate zones are ecologically immature is rejected Niche driven diversity is rejected Rather, production drives diversity
“Community Interactions on Rocky Intertidal Shores”
Pattern’s of Distribution: Vertical Limits The upper limit of rocky intertidal communities is set by the physical environment. Example: Northern facing rocks, spray zones, and places down shore from tidal pools have higher upper limits than areas subjected to increased desiccation, temperatures, and solar radiation. The lower limit of rocky intertidal communities is set by biotic interactions. Example: Chthamalus stellatus and Balanus balanoides could potentially occupy the same space, but Balanus excludes Chthamalus by undercutting, smothering, and crushing Chthamalus restricting Chthamalus to high shore levels.
Pattern’s of Distribution: Horizontal Limit Community zonation is typically associated with the seashore’s energy (wave action): mussels on headlands (turbulent), barnacles in areas of moderate surf, and seaweed in quiet waters in Britain Organisms are specific to these regions -snails and mussels transplanted from quiet to turbulent waters could not hold on! -hydroids and amphipods transplanted from turbulent to quiet waters were silted over -mussels live in quiet and turbulent waters but are eliminated by crabs in the intermediate areas
Pattern’s of Distribution: Interaction between physical and biotic Without refuge at high shore levels where the physical environment limits Balanus, Chthamalus would be unable to exist
Development of the Community There is a sequence of colonization in these rocky intertidal regions: -Diatoms -Fast growing algae -Barnacles and tube worms -Large sessile mussels and fucoid algae -Large algae This could indicate that prior occupation of a site is necessary for the community to fully develop, but -Large algae quickly inhabited fresh sites when they were small and surrounded by a mature community -Large algae has a limited dispersal so their colonization probably takes longer
Development of the Community: Continued Connell criticizes research that indicated facilitative succession plays an integral role in rocky intertidal communities -Facilitative succession was a popular explanation of how communities developed and was compared to organismal development “Based on the evidence, or lack of it, I feel the process of recolonization of intertidal rocky shores should not be described as analogous to the development of an organism” “My purpose is simply to point out the almost complete lack of evidence for any ‘internally controlled’ development toward a ‘mature community”
“Mechanisms of Succession in Natural Communities and their Role in Community Stability and Organization”
The Tone “Clements proposed a theory of the causes of succession so satisfying to most ecologists that it has dominated the field ever since”
Model Application to Reality Model 1 (Facilitation Model): Probably applies to heterotrophic succession of consumers feeding on carcasses, logs, dung, and litter. Additionally, it may apply in special cases where glaciers retreat and pioneer species have to make the soil inhabitable for climax species (spruce) Model 2 (Toleration Model): Only one example provided and the tree was reproducing vegetatively Model 3 (Inhibition Model): Replacement of annual plants by perennials, hardwood trees, corals. Overall, a considerable body of evidence supports this model
Disturbance and Succession
Concluding Remarks Model 1 (facilitation) is commonly cited, but the observed trend usually reflects the passage of time instead of internal control. However, it does occur in nature “This is solely based on analogy, not, in our opinion, on evidence” Model 2 (tolerance) is possible but unusual Model 3 (inhibition) is the most likely Concludes that succession never stops