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