A global perspective of the richness and evenness of traditional crop-variety diversity maintained by farming communities.


Varietal data from 27 crop species from five continents were drawn together to determine overall trends in crop varietal diversity on farm. Measurements of richness, evenness, and divergence showed that considerable crop genetic diversity continues to be maintained on farm, in the form of traditional crop varieties. Major staples had higher richness and evenness than nonstaples. Variety richness for clonal species was much higher than that of other breeding systems. A close linear relationship between traditional variety richness and evenness (both transformed), empirically derived from data spanning a wide range of crops and countries, was found both at household and community levels. Fitting a neutral "function" to traditional variety diversity relationships, comparable to a species abundance distribution of "neutral ecology," provided a benchmark to assess the standing diversity on farm. In some cases, high dominance occurred, with much of the variety richness held at low frequencies. This suggested that diversity may be maintained as an insurance to meet future environmental changes or social and economic needs. In other cases, a more even frequency distribution of varieties was found, possibly implying that farmers are selecting varieties to service a diversity of current needs and purposes. Divergence estimates, measured as the proportion of community evenness displayed among farmers, underscore the importance of a large number of small farms adopting distinctly diverse varietal strategies as a major force that maintains crop genetic diversity on farm.

DOI: 10.1073/pnas.0800607105

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@article{Jarvis2008AGP, title={A global perspective of the richness and evenness of traditional crop-variety diversity maintained by farming communities.}, author={Devra I. Jarvis and Anthony H. D. Brown and Pham Hung Cuong and Luis Collado-Panduro and Luis Latournerie-Moreno and Sanjaya Gyawali and Tesema Tanto and Mahamadou Sawadogo and Istv{\'a}n M{\'a}r and Mohammed Sadiki and Nguyen Thi-Ngoc Hue and Luis Arias-Reyes and Didier Balma and Jwala Bajracharya and Fernando Bances del Castillo and Deepak Kumar Rijal and Loubna Belqadi and Ram B Rana and Seddik Saidi and J{\'e}r{\'e}my Tinga Ou{\'e}draogo and Roger G. Zangre and Keltoum Rhrib and Jos{\'e} L. Ch{\'a}vez and Daniel Sch{\"{o}n and Bhuwon R. Sthapit and Paola de Santis and Carlo Fadda and Toby Hodgkin}, journal={Proceedings of the National Academy of Sciences of the United States of America}, year={2008}, volume={105 14}, pages={5326-31} }