title: A global perspective of the richness and evenness of traditional crop-variety diversity maintained by farming communities.
abstract: 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.
authors: Bioversity International, 00057 Maccarese, Italy. d.jarvis@cgiar.org
authors: Devra I
authors: DI
authors: Jarvis
authors: Anthony H D
authors: AH
authors: Brown
authors: Pham Hung
authors: PH
authors: Cuong
authors: Luis
authors: L
authors: Collado-Panduro
authors: Luis
authors: L
authors: Latournerie-Moreno
authors: Sanjaya
authors: S
authors: Gyawali
authors: Tesema
authors: T
authors: Tanto
authors: Mahamadou
authors: M
authors: Sawadogo
authors: Istvan
authors: I
authors: Mar
authors: Mohammed
authors: M
authors: Sadiki
authors: Nguyen Thi-Ngoc
authors: NT
authors: Hue
authors: Luis
authors: L
authors: Arias-Reyes
authors: Didier
authors: D
authors: Balma
authors: Jwala
authors: J
authors: Bajracharya
authors: Fernando
authors: F
authors: Castillo
authors: Deepak
authors: D
authors: Rijal
authors: Loubna
authors: L
authors: Belqadi
authors: Ram
authors: R
authors: Rana
authors: Seddik
authors: S
authors: Saidi
authors: Jeremy
authors: J
authors: Ouedraogo
authors: Roger
authors: R
authors: Zangre
authors: Keltoum
authors: K
authors: Rhrib
authors: Jose Luis
authors: JL
authors: Chavez
authors: Daniel
authors: D
authors: Schoen
authors: Bhuwon
authors: B
authors: Sthapit
authors: Paola
authors: P
authors: De Santis
authors: Carlo
authors: C
authors: Fadda
authors: Toby
authors: T
authors: Hodgkin
mesh_terms: D044822:Biodiversity; D018556:Crops, Agricultural; D004463:Ecology; D007558:Italy; D012424:Rural Population