Predicting the global incidence of seed desiccation sensitivity

Abstract

Summary The ability of seeds to tolerate desiccation plays an important role in plant regeneration ecology. Globally, the majority of species produce desiccation‐tolerant (orthodox) seeds, while comparatively few produce desiccation‐sensitive (recalcitrant) seeds that are unable to survive dehydration. The trait has important implications for species conservation, as desiccation‐sensitive species cannot be conserved using traditional seed banking techniques. In addition, these species may be less resilient to the increases in droughts predicted for some regions under climate change scenarios. The best available resource on seed desiccation tolerance is the Royal Botanic Gardens, Kew's Seed Information Database. This database contains seed desiccation‐sensitivity data for over 18 000 taxa, approximately 3% of which have desiccation‐sensitive seeds. However, this database is likely biased towards desiccation‐tolerant species. Previous attempts to estimate the proportion of seed plants with desiccation‐sensitive seeds have ranged from 7% to 50%. Here, we aimed to overcome sampling bias to derive a best estimate for the proportion of seed plants with desiccation‐sensitive seeds, based on current data. We used a recently developed method, based on taxonomic relatedness, to account for sampling bias and estimate the proportion of seed plants with desiccation‐sensitive seeds. As a comparison, given that seed desiccation sensitivity is strongly related to habitat, we repeated our analyses using habitat as a basis. The predictions from our taxonomy‐based models ranged between estimates of 7·5% and 19·6% of the world's seed‐plant species with desiccation‐sensitive seeds, depending on model type, while the habitat‐based models suggested a value of approximately 8%. Our evidence suggests that, based on current data, the best estimate of the proportion of species with desiccation‐sensitive seeds is likely to be approximately 8%. Tropical and subtropical moist broadleaf forests had the highest incidence of seed desiccation sensitivity, where an estimated 18·5% of the seed‐plant flora possessed the trait. Synthesis. Alongside our estimation of the numbers of species with desiccation‐sensitive seeds, we provide data on taxa and habitats where this trait may be most prevalent. These findings can be used to support conservation planning, particularly with respect to providing decision support for in and ex situ conservation techniques.

Lack of adequate seed supply is a major bottleneck for effective ecosystem restoration in Chile: friendly amendment to Bannister et al. (2018)

“…Around 80% of Chilean tree species are predicted to have orthodox seeds (León‐Lobos et al ). If the Chilean flora follow global trends (Wyse & Dickie ), the percentage of native shrubs and herbs with high desiccation tolerance should be even higher, particularly in herbs (over 99%). So, conservation in seed banks could be feasible for most native Chilean herbs.…”

The conservation value of germplasm stored at the Millennium Seed Bank, Royal Botanic Gardens, Kew, UK

“…It is shared with policy makers, disseminated to the wider scientific community and general public through mainstream scientific literature, articles, conferences, social media and the RBG Kew website and those of our partners. Although compilation of a full list of research publications is beyond the scope of this paper, recent research studies that used MSB collections or their associated data include Colville et al (2015), Díaz et al (2016) (2017) and Wyse and Dickie (2017).…”

Saving rainforests in the South Pacific: challenges in ex situ conservation

“…The method is therefore only suitable for seeds that are 'orthodox'; that is, tolerant of drying and storage at cold temperatures (Roberts 1973). Tweddle et al (2003) predicted that 50% of non-pioneer woody rainforest species were likely to be intolerant of drying (although recent modelling by Wyse and Dickie (2016) indicates this figure is likely to be much lower when herbaceous species are included). This prediction of desiccation intolerance has meant that, until recently, the seed banking of rainforest species has not been considered a priority, unless a species was particularly threatened or of economic importance.…”

“…Of the 386 genera for which three or more species have been studied, 343 have a very high proportion of species (>95% of those tested) that are suitable for seed banking. However, the data available are biased towards species occurring in dryland areas (Wyse and Dickie 2016), so caution should be used in predicting the storage behaviour of rainforest species based on species already assayed in the same genus.…”