MATING SYSTEM IN PTEROCARPUS-MACROCARPUS KURZ IN THAILAND

The mating system in 11 natural populations of Pterocarpus macrocarpus Kurz in Thailand was investigated based on the mixed mating model usi ng 16 isozyme markers. Single-locus outcrossing rates (t(s)) averaged from 0.620 to 0.931 among populations while multilocus outcrossing rat es (t(m)) ranged from 0.719 to 0.959. Both t(s) and t(m) revealed a ge ographic pattern with western populations exhibiting higher outcrossin g than eastern populations. Low estimates of outcrossing rates in east ern populations could be attributed to habitat characteristics, degree of disturbance, density, and distribution of flowering mature trees, Individual tree outcrossing rates (t(mi)) indicated that reduced popul ation density associated with disturbance could result in low t(m) in some eastern populations.