Interacting forces in a human landscape: Patterns of diversity in an ancient Ethiopian agroecosystem.

摘要

In human systems, changes in climate, land use, culture, and human population pressure affect both the social and ecological landscapes simultaneously, and the same processes that lead to loss of wild biodiversity at species and genetic scales can drive the loss of agricultural diversity and livelihood security as well. This research uses an interdisciplinary approach to gain an holistic understanding of the patterns and processes of diversity in a traditional agricultural ecosystem in the Gamo highlands of southern Ethiopia. The Ethiopian highlands are a global center of crop diversity, and heterogeneous landscapes, traditional agricultural practices, and inaccessibility maintain diverse subsistence agroecosystems. In this study, household interviews on farmer seed exchange are combined with molecular analysis of crop population genetic structure in order to investigate the ways in which biophysical and social landscapes create and maintain diversity in human ecosystems.;In traditional agricultural systems, the scales and mechanisms of seed exchange and selection determine the richness and composition of diversity at landscape, species, and genetic scales. Changing demographic, cultural, or environmental conditions affect patterns of farmer seed exchange, and therefore have effects on agricultural biodiversity. Extensive farmer interviews on seed exchange practices were performed on 121 farms in twelve communities in the Gamo highlands, at a range of elevations and locations. Farmer preferences for seed sources, and the extent to which markets, government extension, and other institutions are accessed for seed, are dependent on elevation, location, and farmer wealth. In the short term, greater dependence on and access to off-farm seed can increase on-farm diversity. However, shrinking farm sizes and cultural change may lead to a reversal of this trend in the future. Support of farmer seed networks and exchange institutions may be an appropriate strategy to conserve agricultural diversity in this system.;These interview data are incorporated into a population genetic analysis of traditional barley varieties (Hordeum vulgare) to determine the ways in which physical and social landscapes interact to distribute diversity in this system. Samples were collected from twelve farmer-named varieties in twelve communities, and were assessed at 14 microsatellite loci. Genetic structure was analyzed using both population-based and individual-based analyses, including traditional measures of population differentiation and genetic distance, multivariate and Bayesian assignment tests. Phenotypic analysis provides information on the ways in which genetic patterns translate into traits identified by farmers. Differential farmer management strategies can lead to markedly different patterns of population structure across elevation classes and barley types. The extent to which farmer seed management appears as a stronger determinant of spatial structure across than the underlying physical landscape highlights the need for the incorporation of social, landscape, and genetic data for the design of conservation strategies in highly human-influenced landscapes.