Content
Topic Introduction
In this topic we look at species richness in detail. It is the diversity of trees that provides the multitude of microhabitats that is one of the factors that enable many sympatric species to survive. In some forests, particularly those on southeast Asia, species from a few families dominate – notably the Dipterocarpaceae. In South America, the Leguminosae are particularly apparent in tropical forests.
We look at some of theories that have been put forward to explain the species richness of tropical forests. These are theories: we still lack an explanation for the astonishing species richness of tropical forests. Some theories have quite a lot of evidence that appears to support them. However, great care is needed to ensure that this is not coincidental, with the true explanation being something else.
Outcomes
By the end of this topic, you should be able to:
- Discuss the factors that result in tree species richness in tropical forests.
- Hypothesize what the importance of tree diversity is for the richness of the other flora and the fauna of tropical forests.
- Summarize the main theories concerning species richness in tropical forests.
- Speculate on which are the most likely explanations of species richness.
- Judge which hypotheses have little value and can be discounted (except perhaps in very particular situations).
- Assess the relevance of particular hypotheses to specific situations.
Topic Readings
Required Readings
- Ghazoul, J. and Sheil, D. 2010. Tropical Rain Forest Ecology, Diversity, and Conservation. Oxford, Oxford University Press, 516 pp. Chapter 8.
Supplementary Materials (Optional)
- Ashton, P. 2014. On the forests of tropical Asia. Less the memory fade. London, UK: Royal Botanic Gardens, Kew. 670 pp.
- Hubbell, S.P. 2001. The unified neutral theory of biodiversity and biogeography. Princeton, New Jersey, USA: Princeton University Press.
- Kricher, J. 2011. Tropical Ecology. Princeton, New Jersey, USA: Princeton University Press, 632 pp. Chapter 5.
Self-check Quiz (For certificate learning only)
After viewing topic presentations, take this self-check quiz to check your own progress. This quiz is designed to see how well you remember some of the more important issues presented in the topic. There are five questions, and each has a potential of 4 answers, only one of which is correct. When you are ready, click the link Self-check Quiz 1.2 to start taking the quiz.
Pre-readings and Discussion (For certificate learning only)
Once you have read Chapter 8 of Ghazoul, J. and Sheil, D. 2010. Tropical Rain Forest Ecology, Diversity, and Conservation, choose to post one thought provoking question related to theories explaining species richness, and answer/respond to at least one other student’s question on Module 1 discussion board Module 1 Discussion.
Graded Assignments (For certificate learning only)
Six Sentence Answer #1
Please refer to the course pages on graded assessments to see details of the Six-sentence Answers (6SA) exercise. You should not attempt to do this assessment until you have read and fully understood the requirements.
The Case
You are a member of a major international forest consultancy firm that specializes in doing surveys of forests around the world. You have access to field teams and the latest surveying equipment, include LiDAR. In the accompanying course, your company was working on the development of forest businesses on a very large island in South-East Asia. You have now moved on to another project, where you are looking at the effects of past and present management practices on the forests and savannahs of East Africa. This area is very diverse, including many different forest types. They range from grass and tree savannahs through seasonally dry woodlands and forests to Afromontane rain forest.
This job that you are working on involves assessing where future reserves should be located. While there are a large number of factors that determine reserve location, you have been told that the top priority is biodiversity. Using the 6SA format, indicate how you would recommend comparing the biodiversity at candidate sites for reserves.
Remember to follow the structure of the 6SA outlined in the section on graded assessments.
Formatting:
- Double-space the text.
- 12-point font in New Times Roman or Calibri.
- Put your name (Family or last name, followed by your first name), student number, the title “Topic 1.1 assignment”, and the date at the top of the first page.
- Name the e-file: your Family or last name_your first name_ Topic 1.1_Assignment.doc (or .docx). Example: Innes_John_Topic 1.1_Assignment (or .docx).
- Standard English usage, clear writing style.
- All assignments should be submitted through Canvas before the deadline.
Topic Summary
In this topic, we have examined some of the many hypotheses that have been proposed to explain the diversity of life found in tropical forest. There is no single hypothesis that can be used to explain every situation, although Steven Hubbell’s unified neutral theory has been suggested as such.
It seems that explaining tropical diversity will remain one of the key questions facing tropical ecologists for a long time. We are only just beginning to understand some of the linkages between organisms in tropical habitats, and indeed many of those organisms still have to be formally described.
Topic Self-review (For self learning)
To review what you have learned in the topic, you are encouraged to use the following reflection questions as a study guide to do a self-review for the topic:
- What factors are thought to result in tree species richness in tropical forests?
- How important is tree diversity for the richness of the other flora and the fauna of tropical forests?
- Which are the most important theories concerning species richness in tropical forests?
- What are the most likely explanations of species richness in tropical forests?
- Which hypotheses purporting to explain tropical diversity are only applicable to very limited situations?
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