TITLE:
Genetic Variation in Tropical Tree Species and Plantations: A Review
AUTHORS:
Tomiwa Victor Oluwajuwon, Racheal Attafuah, Chinedu Joevita Offiah, Doris Krabel
KEYWORDS:
Genetic Diversity, Genetic Variation, Tropical Plantations, Tropical Tree Species, Clonal Forestry
JOURNAL NAME:
Open Journal of Forestry,
Vol.12 No.3,
July
14,
2022
ABSTRACT: The global efforts to restore tropical forests and their productive and
ecological functions through plantation forestry largely depend on the
available genetic variation in the tree species used to establish the
plantations. However, there is limited information on the levels and trends of
the genetic variation and variability of different plantation tree species in
the tropics. Therefore, this study reviews several marker-based studies that
have investigated genetic variation. Most of the top economic species like Eucalyptus
tereticornis and Mansonia altissima are attributed to low levels of
genetic diversity, while others like Pinus caribaea and Swietenia
macrophylla still exhibit high expected heterozygosity
across different populations. However, the levels of genetic diversity
assessed may depend on the markers used. Microsatellites, i.e., simple sequence repeats (SSRs), mostly give higher
estimates when compared to other polymerase chain reaction-based markers. Other factors that typically contribute to
the directional pattern of genetic variation in tropical tree species and populations
include their distribution, density, seed dispersal, succession, and
reproduction. Also, anthropogenic impacts like logging and fragmentation have contributed
to the vast genetic base reduction of many tropical species and populations. Having adequate genetic variation
within the plantation populations is significant in improving their fitness,
resilience, fecundity, productivity, and other ecological functions. It
also provides a basis for tree improvement and breeding in plantation forests.
Although clonal forestry is becoming widespread and considered highly
productive, it is attributed to specific economic, technical, and ecological
risks, such as the increased spread of pests and diseases. Therefore, further
discussions and recommendations to maximise genetic diversity in tropical
(clonal) plantations are provided.