Genetic Diversity and Population Genetic Structure of Teak

Abstract

The increasing demand for teak causes the drastic reduction in the natural teak forests of India, Myanmar, Thailand, and Laos by over exploitation and illegal logging. Reduced tree populations, habitat fragmentation, and isolation results in lower levels of genetic diversity which is critically important for trees to respond to changes in environment, including pests, diseases, and climate. Long-term survival of the population depends on prevention of extinction factors including genetic deterioration caused by inbreeding depression and loss of genetic diversity. Maintenance of small isolated populations for many generations will result in decreasing heterozygosity and loss of allele due to genetic drift and limited gene flow. Genetic variation and population genetic structure of teak was investigated using molecular markers on natural teak populations and landraces. Population genetic studies of teak suggested that India has the highest genetic diversity of teak which is assumed to be the genetic center, and clinal reduction in genetic variation indicated that eastward direction of natural migration route of teak originated from India. Intra-population genetic variation was higher than inter-population variation in teak. Two main distinct genetic clusters in Indian teak populations, four in Myanmar, one in Thailand and Laos, and one separate cluster in Central Laos showed strong genetic structure of natural teak populations. It appears that genetic clusters of teak basically correspond to geographic regions. Teak with high genetic divergence within population and among populations, and significant geographic genetic variation demands maintenance of as much genetic variation as possible, which is critical to a population's evolutionary potential.