Abstract
Ex situ conservation in germplasm and living collections is a major focus of global plant conservation strategies. Prioritizing species for ex situ collection is a necessary component of this effort for which sound strategies are needed. Phylogenetic considerations can play an important role in prioritization. Collections that are more phylogenetically diverse are likely to encompass more ecological and trait variation, and thus provide stronger conservation insurance and richer resources for future restoration efforts. However, phylogenetic criteria need to be weighed against other, potentially competing objectives. We used ex situ collection and threat rank data for North American angiosperms to investigate gaps in ex situ coverage and phylogenetic diversity of collections and to develop a flexible framework for prioritizing species across multiple objectives. We found that ex situ coverage of 18,766 North American angiosperm taxa was low with respect to the most vulnerable taxa: just 43% of vulnerable to critically imperiled taxa were in ex situ collections, far short of a year-2020 goal of 75%. In addition, species held in ex situ collections were phylogenetically clustered (P < 0.001), i.e., collections comprised less phylogenetic diversity than would be expected had species been drawn at random. These patterns support incorporating phylogenetic considerations into ex situ prioritization in a manner balanced with other criteria, such as vulnerability. To meet this need, we present the ‘PIECES’ index (Phylogenetically Informed Ex situ Conservation of Endangered Species). PIECES integrates phylogenetic considerations into a flexible framework for prioritizing species across competing objectives using multi-criteria decision analysis. Applying PIECES to prioritizing ex situ conservation of North American angiosperms, we show strong return on investment across multiple objectives, some of which are negatively correlated with each other. A spreadsheet-based decision support tool for North American angiosperms is provided; this tool can be customized to align with different conservation objectives.
Highlights
Ex situ conservation of plant species in germplasm and living collections is increasingly used to ensure against extinction and provide materials for future restoration efforts [1,2,3]
Common (R5) taxa were most likely to be in an ex situ collection (74%), while apparently secure and critically imperiled taxa were most likely to be in a collection (52% and 49%, respectively), leaving threatened and vulnerable taxa least likely to be held in seed banks or living collections (41% and 42%)
For North American angiosperms, current progress toward achieving the global target for ex situ collections is on par with global efforts (43% of R1, R2, and R3 taxa in at least one ex situ collection relative to 46% globally), but this is still well short of the 2020 target of 75% [4, 5]
Summary
Ex situ conservation of plant species in germplasm and living collections is increasingly used to ensure against extinction and provide materials for future restoration efforts [1,2,3]. Securing more of the world’s flora in ex situ collections is a key component of global plant conservation efforts. In 2009 the Global Strategy for Plant Conservation (GSPC) set a target that 75% of the world’s threatened flora be held in ex situ collections by 2020 and that at least 20% of these collections be available for restoration programs [4]. Species that are more closely related may be more similar in their responses to environmental change [9,10,11,12], functional traits [13, 14], and cultural or economic value [15, 16]—though there are certainly counter examples where phylogeny fails to represent key differences among species [17, 18]. Ex situ collections that are individually or collectively broad in their representation of the ‘Tree of Life’ are likely to capture a wider array of trait variation [19], increasing their value for future uses like ecological restoration [19,20,21,22,23,24]
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