Content
Introduction
The Caatinga is a region of Brazil located in the northeast of the country. It is to the north of the Atlantic Forest biome and to the east of the Cerrado biome. It is dominated by a vegetation type known as caatinga, which comprises seasonally dry tropical forest and woodland. The Caatinga region contains other vegetation types, including savannas, tropical rain forests and rupestrian grasslands, but about 85% of the original vegetation cover was caatinga. The region is dry, with most of it receiving <1000 mm yr-1, although some mountain areas can receive as much as 1800 mm yr-1. There is a pronounced dry season, and towards the centre of the region, some areas may go between 7 and 10 months without rainfall. This has profound effects on the flora and fauna.
Some tropical rain forests today are the remnants of formerly much more extensive rain forests. The caatinga is the remnant of a former area of dry forest that once extended throughout much of central Brazil. it is dominated by small-leaved, thorny trees with twisted trunks, and there is a preponderance of succulents and therophitic herbs. Two major floras exist, one associated with crystalline basement rocks and the other with sandy sedimentary substrates, with the former being more typical.
The origin of the flora and fauna is of considerable interest. The flora appears to have developed through in situ speciation between the Late Miocene and Pliocene periods. The flora of the Sedimentary Caatinga is more recent, and appears to have arisen from ecological speciation during the Pleistocene. The 79 species of lizard found in the region, including 38 endemic species, are of particular interest. They provide many clues to the origins of the caatinga as an ecosystem, and we examine some of these in the presentation.
Outcomes
By the end of this topic, you should be able to:
- Describe the Caatinga region, and the different vegetation types that is contains
- Explain the origins of the species present
- Indicate how they are related
- Explain the lack of large mammals
- Discuss the role that ants play in this region
Readings
Optional Readings
- Gomes Coe, H.H. and Furtado de Sousa, L. de O. 2014. The Brazilian “Caatinga”: Ecology and Vegetal biodiversity of a semiarid region. In: Greer, F.E. (ed.) Dry Forests. Ecology, Species Diversity and Sustainable Management. New York, USA: Nova Publishers. pp. 81-103.
- Silva, J.M.C., Leal, I.R. and Tabarelli, M. (eds.) 2017. The largest tropical dry forest region in South America. Cham, Switzerland: Springer International Publishing. 482 pp.
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 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 5.1.18' to start taking the quiz.
Case Study Discussion (For certificate learning only)
Once you have have read the presentation, post a question about the ecology of the caatinga, and answer/respond to at least one other question on the discussion board Case Study 18 Discussion - Brazil's Caatinga.
Summary
The Caatinga biome of Brazil provides a fascinating example of tropical dry forests. It contains many endemic species as a result of the in situ speciation that has occurred. It represents a remnant of a once more extensive dry forest that extended across much of central Brazil, and its flora and fauna reflect this. Many of the species present are adapted to the long dry season, which in some areas can persist for as long as 10 months. There are few large mammals, principally because the majority need more regular supplies of water than are available. The area is not well studied, and some groups, such as the amphibians, have received relatively little attention. This provides many opportunities for research and further study.
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:
- Can you describe the Caatinga region, and the different vegetation types that is contains?
- Where did the species present come from?
- How are they related?
- Why are there so few large mammals?
- What roles do ants play in this region
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