Gap analysis of priority CWR

There is extensive literature associated with gap analysis, a method which essentially identifies areas in which selected elements of biodiversity are under-represented (e.g. Margules et al. 1988, Margules 1989, Margules and Pressey 2000, Allen et al. 2001, Balmford 2003, Brooks et al. 2004, Dietz and Czech 2005, Riemann and Ezcurra 2005). However, these examples are almost entirely restricted to identifying gaps in habitat or ecosystem conservation, not gaps within existing species or genetic diversity conservation. The use of this technique to identify gaps in networks of protected habitats for in situ conservation of genetic resources, namely for CWR, was first cited by Ingram and Williams (1993). Since then, a systematic gap analysis methodology for identifying gaps in species or genetic diversity conservation has been developed and illustrated with a case study for African Vigna wild relatives. This case study aimed to evaluate the effectiveness of current in situ and ex situ conservation, to identify the ‘gaps’, and therefore assisting the development of conservation strategies for African Vigna genetic resources (Maxted et al. 2008b). More recently, a methodology for collecting crop gene pools for ex situ conservation based on GIS tools has been developed (e.g. Ramírez-Villegas et al. 2010, Castañeda-Álvarez et al. 2015, Khoury et al. 2015a,b, Castañeda-Álvarez et al. 2016).

The results of the diversity analyses (distribution and ecogeographic diversity and genetic diversity) as well as novel threat assessment provide the information needed to identify gaps in current in situ and ex situ conservation actions for CWR. The Figure below summarises how these analyses feed into a gap analysis study.

Conservation gaps (both in situ and ex situ) can be detected at different levels (see Figure below):

1. Individual CWR taxon level (CWR taxa not conserved versus taxa conserved).
2. Ecogeographic level (for a particular CWR, areas/environmental conditions not covered by in situ or ex situ conservation activities versus those covered).
3. Trait level (specific CWR populations that hold a particular trait of interest that are not conserved versus populations with that same trait that are).
4. Genetic diversity level (specific CWR populations that are genetically important that are not conserved versus those that are).

The level(s) at which gap analysis can be undertaken depends on the types of data available for the study. It should be highlighted that genetic data are not always available and that the collation of information de novo may not be possible due to resource limitations. Therefore, in the absence of ‘real’ genetic information, ecogeographic diversity information is often used as a proxy. The result of an in situ gap analysis is the identification of in situ conservation priorities, while the result of an ex situ gap analysis is the identification of additional CWR germplasm collections that are required.