Topic Introduction

In this topic, we examine flowering and pollination, and also the presence of genetic neighbourhoods in tropical forests. As you have already learnt, individuals of a species may be widely spaced in a tropical forest. This raises the question of how they are pollinated. In moist forests, the majority of plants are pollinated by animals (including birds, mammals, insects, and other animals), with wind being relatively unimportant. In dry forests, wind is more important, and is the dominant agent for the dispersal of pollen amongst grasses.

Some plant species have developed very specialized floral structures associated with equally specialized pollinators. Other plants are pollinated by a range of different organisms. This is an area where new knowledge is constantly being acquired, and it now evident that some species are not as specialized as previously thought.

Triggers for flowering vary widely, but in the event of mass flowering is seems likely that there is an environmental cue that multiple species respond to. In some cases, the cue is a drought associated with ENSO cycles, but this is not a universal explanation. Species differ in the frequency of flowering: pioneer species may flower several times a year, or even continuously, whereas species found in mature forests tend to flower only once a year.

We also examine the concept of genetic neighborhoods in this topic. These are an important aspect of the gene flow within tropical forests. Fine-scale spatial genetic structures provide a means to estimate indirectly the gene flow within plant populations, so are covered in some detail.

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

• Describe the main pollination mechanisms for plants in tropical forests.
• Compare flowering patterns in tropical moist and tropical seasonally dry forests.
• Contrast the effectiveness of different pollination mechanisms.
• Discuss, using examples, the importance of gene flow within tropical forests.
• Describe how genetic structures in tropical forests can develop.
• Compare the importance of gene flow through pollen and seed transfers.

Topic Readings

Required Readings

• Ghazoul, J. and Sheil, D. 2010. Tropical Rain Forest Ecology, Diversity, and Conservation. Oxford, Oxford University Press, 516 pp. Sections 12.1 and 12.3.

Optional Readings

• Crawley, M.J. (ed.) 1997. Plant Ecology. 2^nd Oxford, UK: Blackwell Scientific. 717 pp. Chapter 6.

• Proctor, M., Yeo, P., and Lack, A. 1996. The natural history of pollination. 2nd edition. London, UK: Harper Collins. 384 pp. 

Fundamental Concepts

PPT Presentations

This topic contains two presentations:

3.1.1 Plant reproduction - Flowering.pptx Download 3.1.1 Plant reproduction - Flowering.pptx

3.1.2 Plant reproduction - Genetic neighbourhoods.pptx Download 3.1.2 Plant reproduction - Genetic neighbourhoods.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 3.1 to start taking the quiz.

Pre-readings and Discussion (For certificate learning only)

Once you have read Sections 12.1 and 12.3 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 3 discussion board Module 3 Discussion. 

Graded Assignments (For certificate learning only)

Six Sentence Answer #6

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. Your company is working on a contract 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.

The landscape ecologist in your team has stressed the importance of created forested corridors connecting different areas of forest. This will require planting significant numbers of forest trees. You will have to choose which species to use, and create nurseries to grow the seedlings. Using the 6SA approach, justify the key strategy you will use to ensure sufficient diversity, both within and between species?

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 you have examined the variety of pollination mechanisms used by plants. You have seen that there is an enormous variety of pollinators, and that there are many different mechanisms involved, especially when it comes to rewarding the pollinators. These are important species-to-species interactions, a topic that we will be returning to in the next module.

You have also looked at genetic neighborhoods and touched on the way that genes are moved across the landscape. This can occur either by pollen movement or by movement of the seeds, a subject examined in the next topic in this module.

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 are the main pollination mechanisms for plants in tropical forests?
• How do flowering patterns compare in tropical moist and tropical seasonally dry forests?
• How many different groups of pollinators can you name?
• How effective are the different pollination mechanisms?
• How important is gene flow within tropical forests, and how does it occur?
• How do genetic structures in tropical forests can develop?
• Is gene flow through pollen more important than through seed transfers? If so, why?