A gap analysis modeling framework to prioritize collecting for ex situ conservation of crop landraces

Aim: The conservation and effective use of crop genetic diversity is
crucial to overcome challenges related to human nutrition and agricultural
sustainability. Farmers’ traditional varieties (“landraces”) are major
sources of genetic variation. The degree of representation of crop
landrace diversity in ex situ conservation is poorly understood, partly
due to a lack of methods that can negotiate both the anthropogenic and
environmental determinants of their geographic distributions. Here we
describe a novel spatial modeling and ex situ conservation gap analysis
modeling framework for crop landraces, using common bean (Phaseolus
vulgaris L.) as a case study. Location: The Americas Methods: The modeling
framework includes five main steps: (1) determining relevant landrace
groups using literature to develop and test classification models; (2)
modeling the potential geographic distributions of these groups using
occurrence (landrace presences) combined with environmental and
socioeconomic predictor data; (3) calculating geographic and environmental
gap scores for current genebank collections; (4) mapping ex situ
conservation gaps; and (5) compiling expert inputs. Results: Modeled
distributions and conservation gaps for the two genepools of common bean
(Andean and Mesoamerican) were robustly predicted and align well with
expert opinions. Both genepools are relatively well conserved, with Andean
ex situ collections representing 78.5% and Mesoamerican 98.2% of their
predicted geographic distributions. Modelling revealed additional
collection priorities for Andean landraces occur primarily in Chile, Peru,
Colombia and, to a lesser extent, in Venezuela. Mesoamerican landrace
collecting priorities are concentrated in Mexico, Belize, and Guatemala.
Conclusions: The modeling framework represents an advance in tools that
can be deployed to model the geographic distributions of cultivated crop
diversity, to assess the comprehensiveness of conservation of this
diversity ex situ, and to highlight geographic areas where further
collecting may be conducted to fill gaps in ex situ conservation.