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Prioritizing the CWR checklist

Why do we need to prioritize CWR for active conservation?
The creation of a CWR national checklist is likely to identify a greater number of taxa than can be actively conserved due to resource limitations, especially if applying the broad concept of CWR (all the taxa within the same genus as a crop). Therefore, the process of establishing priorities for CWR conservation is an obvious and essential step in CWR conservation planning.

Beta macrocarpa Guss, a primary wild relative of and potential gene donor to cultivated beets namely of salt tolerant genes; it is Endangered (EN) at European level; here it is pictured in Quinta de Marim (Ria Formosa Natural Park, Portugal). (Photo: Maria Cristina Duarte)

There has been considerable debate about how species, in general, should be prioritized for conservation and about which criteria should be used (e.g. Fitter and Fitter 1997, Maxted et al. 1997). Possible criteria include: threat of genetic erosion, endemicity, rarity and population decline (Whitten 1990, Department of Environment 1996, Sapir et al. 2003), quality of habitat and intrinsic biological vulnerability (Tambutii et al. 2001), species abundance in relation to their geographical range size (Hoffmann and Welk 1999), “responsibility for the conservation of a species” (estimate of the geographic proportion of a species distribution in a certain country against the worldwide distribution) (Schnittler and Günther 1999), recovery potential, feasibility and sustainability of conservation (Whitten 1990), taxonomic uniqueness (Vane‐Wright et al. 1991, Faith 1992) and genetic distinctiveness, phylogenetic criteria and the ability of a species to speciate within "new" environments (Linder 1995), cultural importance (Norton 1994, Dhar et al. 2000), economic factors (Bishop 1978) and socio‐economic use, current conservation status, ecogeographic distribution, biological importance, legislation, ethical and aesthetic considerations, and priorities of the conservation agency.

Specifically regarding the establishment of CWR conservation priorities, several different criteria and numerous methods  [2] have been used depending on the needs and available resources of individual countries and/or the conservation agencies within the countries that are undertaking the prioritization exercise. Relatively recent studies have shown how CWR can be prioritized globally (Maxted and Kell 2009, Vincent et al. 2013), regionally (e.g. Ford‐Lloyd et al. 2008) and nationally (e.g. Maxted et al. 2007, Magos Brehm et al. 2010, Kell et al. 2015). At each scale, the economic value of the related crop (hence breeder demand), the potential utilization for crop improvement (i.e. degree of relatedness of the wild relative to the crop/ease of crossing with the crop), and relative level of threat are the most commonly used criteria (Barazani et al. 2008, Ford-Lloyd et al. 2008)—prioritization methods usually use a combination of all three of these criteria.

An alternative, and more flexible, approach is to assign different levels of conservation priority to CWR—still based on the selected prioritization criteria—rather than identifying a list of equally important priority CWR. The top priority CWR are thus a number of taxa for which it is reasonable to consider implementing active conservation. In this way, a more extensive list can be more easily and objectively justified, maintained and updated, and taxa that are not of immediate priority may be given conservation attention at a later date. In addition, by using this approach, some of the taxa that are of less immediate conservation priority may occur within the same sites as those of highest priority, so they could be captured in the same in situ CWR conservation sites and targeted when collecting higher priority taxa for ex situ conservation.

However, whichever prioritization methodology and criteria are used, the total number of target CWR should be adjusted to a number that can be actively conserved using available financial and human resources. There is no precise way of estimating the most appropriate number of target CWR and so any estimate will be subjective.

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