Effects of Dry Tropical Forest Fragmentation on the Reproductive Success and Genetic Structure of the tree Samanea saman

background

Tropical trees are particularly vulnerable to forest fragmentation due to low population densities and reproductive self-incompatibility. Forest fragmentation is likely to decrease gene flow, increase endogamy, and eventually produce a high differentiation among remnant populations.

research goals & methods

This study evaluates the effect of forest fragmentation on the reproductive success, progeny vigor, and genetic variation of the tropical dry-forest tree Samanea saman. The study compares the probability of natural pollination, seed production, genetic variation, and progeny vigor of trees in isolation and in continuous populations. Flowers of trees in both locations received similar pollen loads, but the trees in continuous populations were significantly more likely to produce a mature fruit. Fruits of trees from continuous populations produced similar numbers of seeds as isolated trees did and had a similar probability of seed abortion, although had greater rates of seed predation.

conclusions & takeaways

Although the numbers of viable seeds produced under both conditions were similar, seeds produced by trees from continuous populations were more likely to germinate and to produce greater leaf area and biomass as seedlings than progeny from isolated trees. A genetic analysis of progeny showed that levels of genetic diversity in trees in isolation and in continuous populations were comparable. The effective self-fertilization rate and inbreeding coefficient of the progeny were slightly higher for isolated trees than for trees in continuous populations. We concluded that the fragmentation of tropical dry forests affects the genetic variation and vigor of S. saman progeny. Isolated trees showed high reproductive capacity, however, in spite of their habitat condition.