CIFOR’s research programme on conservation of tropical forest genetic resources

The research programme described is intended to comprehensively answer key questions relating to in situ conservation of genetic resources. Outputs will be in the form of models of how landscape processes affect genetic level processes, and in the form of management prescriptions or policy options. In the case of research on tools and methodologies, outputs will obviously be improved methods for assessment of genetic diversity. There are strong links to various elements of CIFOR's research agenda. The links to socio-economic research of CIFOR's Policy and Social Science scientists are obvious and have been emphasised throughout. In addition, there are links to the Forest Ecosystem Management initiative under the Natural Forest Management Division, especially to the activities dealing with measurement of biodiversity and impacts of human activity on biodiversity, and to various activities in the Research Support Division. These include efforts to model the human-forest interface, and the development of GIS technology

Estimating sample size for inference about the Shannon-Weaver and the Simpson Indices of species diversity

A framework for a priori estimation of the expected sampling variances of the Shannon-Weaver and the Simpson indices of species diversity is developed by the introduction of the most probable relative species abundance distribution (MOPSAD). MOPSAD gives the prior probability of a species' relative abundance. The beta distribution is used here as the prior for MOPSAD. Sample sizes needed for efficient statistical inference and hypothesis testing about the two indices are provided for 16 distinct beta priors for MOPSAD. Shannon-Weaver and Simpson's diversity indices in plant communities expected to have a `U'-shaped or a J-shaped MOPSAD will have large sampling variances. For the same statistical resolution the Simpson index requires about nine times as many samples as the Shannon-Weaver index. The impact of a positive or negative spatial association among species on the variance of the diversity indices was also assessed. In general, spatial association had little impact on the variance of the indices; it suffices to increase the sample size by about 5% as a safeguard against variance inflation due to spatial associations

Measuring and monitoring biodiversity in tropical and temperate forests: proceedings of a IUFRO symposium held at Chiang Mai, Thailand August 27th-September 2nd 1994

Many estimates suggest that the world’s forests are home to more than 50% of terrestrial biodiversity, yet temperate and tropical forests face numerous threats, including agricultural and industrial expansion, climate change, non-sustainable management and pollution. If forests and their diversity of living organisms are to be conserved, there is a need to measure and monitor biodiversity, in order that the impact of human activities and the efficacy of conservation measures can be assessed. As the concept of biodiversity covers the range of life itself, from genes to ecosystems, measurement and monitoring is extremely complicated

Genetic resources for plantation forestry

Relatively few tropical species have been used extensively in plantations. Species of pines and eucalypts are used in about one-third of the total area of tropical forest plantations, and acacias are also commonly planted. In utilising genetic resources effectively, it is important to assess the relative contributions of the genotype and the environment to the phenotype, and the relative magnitude of genetic variation at each level in the genetic hierarchy: species, provenances, and down to individual trees. The significance of quantitative variation and molecular genetics in the selection of genetic resources is discussed and the use of these different types of information in the design and implementation of tree improvement strategies described. Diff erent approaches to the selection of genetic resources at each level of the genetic hierarchy are reviewed with particular reference to selection for water and nutrient use efficiency. While marker-aided selection, physiological testing and modelling may be valuable in the future, traditional field testing remains an absolute necessity

The population genetic consequences of habitat fragmentation for plants

Habitat fragmentation reduces the size and increases the spatial isolation of plant populations. Initial predictions have been that such changes will be accompanied by an erosion of genetic variation and increased interpopulation genetic divergence due to increased random genetic drift, elevated inbreeding and reduced gene flow. Results of recent empirical studies suggest that while genetic variation may decrease with reduced remnant population size, not all fragmentation events lead to genetic losses and different types of genetic variation (e.g. allozyme and quantitative variation) may respond differently. In some circumstances, fragmentation actually appears to increase gene flow among remnant populations, breaking down local genetic structure

Disturbance-induced density-dependent reproductive success in a tropical forest tree

The reproductive output of Shorea siamensis, a widespread dipterocarp tree, was assessed in relation to disturbance and tree density at three sites in western Thailand during the 1996 and 1997 flowering seasons. The locations were similar except in disturbance history, which was reflected in decreasing tree density from undisturbed via moderately disturbed to disturbed sites. Hand pollination experiments showed S. siamensis to be partially self-incompatible due to differential pollen tube growth and abortion of inbred fruit. Although more than 90% of flowers from trees at all sites were pollinated, pollen tubes developed in only a small proportion of these flowers. Both pollen tube development and initial fruit production were highest at the undisturbed site. Many fruit, presumably selfed, were aborted during development at all sites, but significantly more fruit were aborted at the disturbed site, resulting in lowered production of mature fruit. S. siamensis was pollinated by small Trigona bees, which exhibited significant declines in intertree movements with increasing distance between flowering trees. As resource availability did not differ between sites, differences in mature fruit set were considered to be mediated by changes in pollinator foraging behaviour at different tree densities. Variation in seed set was negatively correlated with distance to nearest conspecific both within and between sites. At the two least disturbed sites observed seed set values corresponded with those expected by calculation. However, seed set at the disturbed site was significantly lower than expected. The results suggest that high reproductive success of S. siamensis is dependent upon cross-pollination, which, through pollinator behaviour, is a function of tree isolation. This species may thus be subject to the Allee effect, where population viability is reduced disproportionately with a decline in population size or population density. The implications of these results for population recovery and genetic structure following disturbance are discussed