Agroforestry ecosystems may be an important resource for conservation and sustainable use of tropical trees, but little is known of the genetic diversity they contain. Inga edulis, a widespread indigenous fruit tree in South America, is used as a model to assess the maintenance of genetic diversity in five planted vs. five natural stands in the Peruvian Amazon. Analysis of five SSR (simple sequence repeat) loci indicated lower allelic variation in planted stands [mean corrected allelic richness 31.3 (planted) and 39.3 (natural), P = 0.009]. Concerns regarding genetic erosion in planted Amazonian tree stands appear valid, although allelic variation on-farm is still relatively high.

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Valuable tree genetic resources are declining around many farming communities in the Peruvian Amazon, limiting farmers' options for economic development. The International Centre for Research in Agroforestry is working with farming communities to increase productivity and long-term sustainability of their forests, and to empower them to conserve tree genetic resources. This paper describes some principles of participatory tree domestication, and how researchers are working with farmers to select improved planting materials, reduce the risk of poor tree adaptation, produce and deliver high-quality planting material, and scale up participatory tree domestication.

Hundreds of native tree species are currently found in extensive agroforestry ecosystems in the Peruvian Amazon, forming an important reservoir of biodiversity. To further promote conservation, farmers are encouraged to supplement intra-specific genetic diversity in these populations with seed collected from local forests. For some tree species, however, this approach may be inappropriate, as stands of these taxa already found on-farm may not be of local origin. Despite this issue being of importance for conservation, little information is available on the history of cultivated trees in the region, a situation that we here rectify for the important fruit tree Inga edulis.Based on nuclear SSR and chloroplast DHPLC analyses of closely geographically matched natural and planted stands at five sites, it appears that cultivated material of I. edulis is primarily of non-local origin, indicating that conservation based on new wide-scale infusions from local wild stands into farms may be inappropriate in the region. Although nuclear and chloroplast diversity were both lower in planted stands, values were still relatively high (~80 and 70% of natural stands, respectively), indicating that when farmers plant trees, good collection practice of seed from already cultivated I. edulis should be an effective means for ensuring long-term conservation on farms.

Peach palm ( Bactris gasipaes Kunth) is cultivated for fruit and 'heart of palm', and is an important component of agroforestry systems in the Peruvian Amazon. In this study, AFLP was used to compare genetic diversity among domesticated populations along the Paranapura and Cuiparillo rivers, which are managed by indigenous and colonist farming communities, respectively. Gene diversity was 0.2629 for the populations in indigenous communities and 0.2534 in colonist communities. Genetic differentiation among populations ( G(st)) was 0.0377-0.0416 ( P<0.01) among populations along both rivers. There was no relation between genetic differentiation and the geographical location of populations along the rivers. Since natural seed dispersal by birds and rodents is thought to occur only across relatively short distances (100-200 m), it is likely that exchange of material by farmers and commercial traders is responsible for most of the 'long-distance' (over more than 20 km) gene flow among populations along the two rivers studied. This exchange of material may be important to counteract the effects of selection as well as genetic drift in small groups of trees in farmers' fields, much as in a metapopulation, and may account for the weak genetic differentiation between the two rivers ( G(st)=0.0249, P<0.01). A comparison with samples from other landraces in Peru and Brazil showed the existence of an isolation-by-distance structure up to 3,000 km, consistent with gene flow on a regional scale, likely mediated by trade in the Amazon Basin. Results are discussed with regard to practical implications for the management of genetic resources with farming communities.

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Calycophyllum spruceanum Benth. is an important tree for timber and energy in the western Amazon, with expanding national and international markets for its wood. There is relatively little information, however, about geographic variation in tree growth and wood properties, and correlations among these traits. The first provenance trial was established with farming communities in the Peruvian Amazon. Seven provenances, sampled from regions near the equator, were tested in three planting zones located in one watershed. Variation and correlations were investigated in stem growth at 30 and 42 months, wood density (in the lower and upper parts of the stem) and mean heat content of stem wood at 32 months. Stem height varied significantly among provenances and planting zones, but zones accounted for much more variation than provenances. Stem wood traits did not vary significantly among provenances. Wood density was greater in the lower than in the upper stem. Wood density in the upper stem and the difference in density between the lower and upper stem varied significantly among planting zones: density in the upper stem was lowest, and the difference in density between the lower and upper stem was largest in the zone where trees grew most rapidly. Phenotypic correlations between stem growth and wood density differed in sign among planting zones, suggesting that selecting fastgrowing trees could indirectly reduce wood density in environments where trees grow slowly, and increase the difference in wood density between the lower and upper stem in environments where trees grow very rapidly. Correlations between stem growth and wood heat content were stable across zones, and indicated that larger trees tended to have wood with higher heat content. Stem-wood heat content varied with provenance latitude/ longitude in the sample region, but none of the other traits varied clinally. Results indicate that there is potential to select faster-growing provenances at an early age, but this could affect wood density in certain environments.

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