manual on taxonomy of Acacia species


Cover: A Bruchid beetle, of the type found in Acacia.
(Actual size, 2.5–3.0 mm).

Present taxonomy of four species of Acacia
(A. albida, A. senegal, A. nilotica, A. tortilis)

J.P.M. Brenan

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The importance of conserving and utilizing existing genetic variation is recognized as fundamental in most tree species used in large-scale industrial plantations. However little or no information is yet available on intra-specific variation in a large number of tropical species which today are receiving increased attention as providers of goods and services for rural communities.

Following the recommendations made by the FAO Panel of Experts on Forest Gene Resources and with financial support from the International Board for Plant Genetic Resources (IBPGR), FAO's Forestry Department initiated in 1979 a project on the conservation and better utilization of genetic resources of arboreal species for the improvement of rural living. Based on a list of species drawn up by the FAO Panel and in accordance with the wishes expressed by the future cooperators, priority has been initially given to a few selected species mainly in the genera Acacia and Prosopis.

The general objectives of the project are the conservation and improved utilization of genetic resources of multi-purpose arboreal species growing in arid and semi-arid areas. The means of achieving these objectives are exploration, collection of reproductive material (mainly seed) and evaluation of genetic variability and adaptability to varying environmental conditions of the species included. These activities will enable appropriate action to be taken in conservation in situ and ex situ and in planting well-adapted and otherwise suitable species and provenances in village woodlots, firewood plantations, for food and fodder, and for shade, shelter and land amelioration.

As the species included in the project have not in the past received much attention, little information and experience are available on fundamentally important aspects such as taxonomy and seed collection, handling, storage and treatment. Where such information exists, it is often scattered and difficult to obtain. Yet, the species present a number of serious problems in these specific fields: their taxonomy is often confused and a number of interbreeding species complexes are thought to exist, making proper identification difficult and predictability of performance in subsequent generations impossible; seed collection and handling are difficult because of the scattered, often remote stands in which the trees occur, irregularity of good seed years, difficulty of extraction and uncertainties on safe but efficient methods of breaking the seed dormancy. Last, but not least there are the problems caused by insects in all stages of development and storage of the seeds.

In order to remedy at least in part these identified information gaps it was decided to prepare a series of handbooks within the framework of the FAO/IBPGR project. Such handbooks, aimed at professional staff involved in actual field operations, have been prepared on taxonomy; seed collection, handling, treatment and storage; and seed insects of the two main genera, Acacia and Prosopis. The handbooks are published in English, French and Spanish to help bridge language barriers between countries and continents.

We are aware of the fact that much more work is still needed in this field: the species covered are only a small fraction of those which merit urgent attention, the topics covered in these handbooks are but a few of the numerous ones which need to be systematically tackled. However, through this and related work we hope to catalyze action elsewhere in the world, to show one of the ways of going about the problems which we all should be determined to solve: the conservation of our heritage of genetic resources and the utilization of these resources for the betterment of life particularly of rural communities dependent on these resources.


The author is grateful to Professor E.A. Bell, Director of the Royal Botanic Gardens, Kew, for permission to reproduce photographs and drawings and for working facilities.

Dr. G.A. Wickens gave much help and advice, including the making available of literature, references and photographs. Thanks are also due to Dr. R. Polhill.

Miss Eleanor Huxley kindly prepared various drawings (figs.4, 11 and 16) and maps (figs.3, 5, 10, 17). Mrs. Joan Curtis typed the report with admirable care.

Finally, the author expresses his gratitude to his wife for so much and varied help during the preparation.

Rome, © FAO 1983

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This electronic document has been scanned using optical character recognition (OCR) software. FAO declines all responsibility for any discrepancies that may exist between the present document and its original printed version.



1.1    Background to and outline of study

1.2    Concordance

1.3    Occurrence of species, etc., in participating countries


2.1    Relationship

2.2    Generic Position

2.3    Recognition

2.4    Summary of previous taxonomic work

2.5    Brief description

2.6    Synonymy

2.7    Distribution

2.8    Variation

2.9    Further work needed

2.10  Literature consulted and cited


3.1    Recognition and relationship.

3.2    Summary of previous taxonomic work

3.3    Brief description

3.4    Distribution

3.5    Variation

(i)    Introduction

(ii)   Key to varieties

(iii)   Descriptions, synonymy and distributions of varieties

3.6    Further work needed

3.7    Literature consulted and cited


4.1    Recognition and relationship

4.2    Summary of previous taxonomic work

4.3    Brief description

4.4    Distribution

4.5    Variation

(i)    Introduction

(ii)   Key to subspecies

(iii)   Description, synonymy and distributions of subspecies

4.6    Further work needed

4.7    Literature consulted and cited


5.1    Recognition and relationship

5.2    Summary of previous taxonomic work

5.3    Brief description

5.4    Distribution

5.5    Variation

(i)    Introduction

(ii)   Key to subspecies and varieties

(iii)   Descriptions, synonymy and distributions of subspecies and varieties

5.6    Further work needed

5.7    Literature consulted and cited