Topic Introduction

Everything that you have covered so far in this module has been about the rich diversity of species found in tropical forests. Many of the species are common, whereas others are quite rare. What circumstances enables a species to dominate to the extent that a single tree species can form monodominant stands within a forest? At the other end of the spectrum, what circumstances enable a species to have restricted ranges or occur at very low densities within a forest, perhaps with only one or two individuals within a 50 hectare area?

In this final topic of Module 1, we will look at these issues.

Outcomes

By the end of this topic, you should be able to:

• Contrast the reasons why a species may be widespread and super-abundant while another is very rare or has a very restricted ranges.
• Explain how very rare species can continue to survive in tropical forests.
• Discuss the significance of high mountains for species diversity in the Tropics.
• Explain why some species, such as Ceiba pentandra, are so widely distributed.
• Propose why some widespread species may not be as widespread as previously thought.
• Hypothesize why monodominant stands are present in the Tropics.

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.

Optional Readings

• Kricher, J. 2011. Tropical Ecology. Princeton, New Jersey, USA: Princeton University Press, 632 pp. Chapters 6 and 7

Fundamental Concepts

PPT Presentations

This topic contains a single presentation:

1.3.1 Restricted range species and widespread generalists.pptx Download 1.3.1 Restricted range species and widespread generalists.pptx

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 1.3 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 the material that you have read, 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)

There is no graded assignment associated with this topic.

Topic Summary

In this topic, we examined both rare species and very common species. We also looked at how trees can form monodominant stands in some tropical regions. Encountering such a stand can be very surprising – a single tree species may dominate a large area in startling contrast to the surrounding forest. As with diversity, there is now single explanation for the occurrence of such stands, and they remain an enduring question for tropical ecologists.

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:

• Why are some species widespread and super-abundant while others are very rare or have very restricted ranges?
• How do very rare species continue to survive in tropical forests?
• What is the significance of high mountains for species diversity in the Tropics?
• Why some species, such as Ceiba pentandra, so widely distributed?
• Are there any reasons to question whether species that are thought to be very widespread really are?
• How do monodominant stands develop?