Topic 3.2. Floral characteristics

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Topic Introduction

In this topic we will introduce you to some of the incredible diversity of plants that exists in tropical forests. It is the plants within tropical forests that create the habitat for everything else, and so a sound understanding of the different components that make up a tropical forest flora is important.

There are very few people capable of identifying the majority of plants in a tropical forest. You should develop plant (and animal) identification skills applicable to the region that you are working in. We cannot emphasize enough that using a cellphone application to identify plants is inappropriate, and will likely always remain so. There is a role for apps in the identification of some groups of organisms, but this does not include the tropical forest plants.

We have structured this module into two main groups of presentations. In the first group, we describe about 100 families of plants. The families presented here are the same as chosen by Utteridge and Bramley (2015). These families were chosen through a rudimentary analysis of pantropical plot data that revealed the most widespread and common families. We provide some details about the distribution of the family, the form of the species and then provide some key identification points, as identified in Utteridge and Bramley (2015), supplemented with information from several other sources. Finally, for each family, we provide pictures of a few examples. These are not necessarily characteristic species – rather, we have attempted to show the variety of plant forms that can be encountered in tropical forests.

In the samples, we have generally provided photos of the foliage of the species in question. Why not the flowers, when they are usually the most important characteristic for identification? A visit to a tropical forest, particularly a rain forest, will quickly provide the answer. Unless you are very lucky, most of the species that you encounter will not be in flower. With the trees, if they are in flower, the flowers may be in the upper canopy, invisible from the ground. In many cases, it may even be difficult to see the foliage, especially of emergent and trees in the upper canopy. Many epiphytes may also be invisible from the ground. There are now a few canopy walks, in different parts of the world that provide access to the canopy, and in montane forests it may occasionally be possible to get glimpses of the canopy below an observation point. Generally, however, the canopy will be inaccessible to most forest visitors. Spent flowers and fruits may be present on the ground, but it is not always possible to determine which tree they have come from.

In the second group of presentations, we have looked at the remaining families found in the tropics. Some of these may be particularly abundant in specific areas, but because they are limited in distribution, they are not included in the first group. We provide less information about these (it would otherwise be even more overwhelming than it already is), and do not provide floral characteristics used in identification. We have also provided fewer examples, again in the interest of keeping the presentations to a manageable size.

A final presentation in this module deals with the main floral characteristics of the five tropical regions. We will return to this subject several times in the accompanying course.

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

  • Describe some of the more important plant families found in tropical forests.
  • Explain how you would go about familiarizing yourself with the flora of tropical forest.
  • Compare  and contrast the floras of different tropical forest areas.
  • Outline the origins of these variations.
  • Interpret the significance of regional differences in tropical forest floras.
  • Contrast the evolutionary development of the floras of the five tropical regions.
  • Conclude why differences exist between the areas.

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