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A selection of the rainforest fruits collected representing fleshy and dry, dehiscent and indehiscent fruit types: aArchidendron hendersonii; bCryptocarya laevigata; cSloanea woollsii; dArgyrodendron trifoliolatum; eEmmenosperma alphitonioides; fDavidsonia pruriens; gPittosporum angustifolium; hCynanchum elegans; and iDysoxylum fraserianum
Source publication
Seed banking of rainforest species is hindered by lack of knowledge as to which species are tolerant of desiccation and freezing. We assessed 313 Australian rainforest species for seed banking suitability by comparing the germination percentage of fresh seeds to seeds dried at 15% RH and seeds stored at −20 °C after drying. We then compared desicca...
Citations
... However, the limited supply diversity of species from rainforests in commercial markets may be related to factors such as seed storage longevity and a lack of optimised protocols for storage and germination (Sommerville et al., 2021). For instance, Sommerville et al. (2021) observed reduced viability in long-term storage for rainforestrestricted species relative to seed of species from drier environments. ...
... However, the limited supply diversity of species from rainforests in commercial markets may be related to factors such as seed storage longevity and a lack of optimised protocols for storage and germination (Sommerville et al., 2021). For instance, Sommerville et al. (2021) observed reduced viability in long-term storage for rainforestrestricted species relative to seed of species from drier environments. ...
Societal Impact Statement
Large quantities of diverse native seeds are required to scale up global restoration efforts. However, it remains unclear for many ecosystems how the diversity of available seed in commercial stocks reflects the composition of the ecosystems where vegetation is being remade. This study highlights existing shortfalls in the diversity of seed presently available for use in restoration and identifies gaps in the seed supply chain while providing a new method for optimising species selection given these constraints. This work underscores how improved collaboration between stakeholders is required to strengthen the seed supply chain and help remake functionally diverse vegetation.
Summary
Restoration using native seed is frequently implemented to restore degraded ecosystems. However, it remains unclear how constraints on the diversity of germplasm available for use in restoration may limit the recovery of both species and plant functional diversity.
Using a dataset of seed availability for Australia's major vegetation types, we explore variation in the diversity and breadth of functional traits (leaf mass per area, seed mass, plant height) for species where seed is available on commercial markets relative to unavailable. Using these data, we simulate theoretical seed mixes derived from two species pools: (1) constrained by the current market of commercially available seed, and (2) assuming all native species can be planted; then we compare differences in functional diversity (dispersion) as an exercise to explore possible limitations within the current seed supply.
Seed from only 12% of Australian plant species (2992 species) is presently available for immediate purchase. Seed was more frequently available for trees and shrubs than for understorey species. Available species were on average taller, with thicker, longer‐lived leaves than unavailable species. Overall, functional dispersion was lower for seed mixes generated using available seed compared with those drawn from all species.
Solutions are required to address seed shortfalls so that plantings are not only species rich but also functionally diverse. We develop two options: (1) quantifying and addressing gaps in the seed supply chain that currently limit the capacity for practitioners to restore diverse vegetation; and (2) applying a trait‐informed species‐selection method to plantings that maximises functional diversity using available seed.
... Because the majority of obligate and near-obligate resprouter species had a continuous size-class distribution indicating on-going recruitment of new individuals from seed (some species produced clonal recruits), it appears this occurs between fires and seedlings can attain fire resistance before the next fire (Fensham et al. 2003). Most were mature phase rainforest/mesophyll species that produce non-persistent, recalcitrant seed (Sommerville et al. 2021) destroyed by fire. Freshly fallen fruit were observed under canopy-intact trees of some of these species in Year 1 (e.g. ...
Context Species fire responses were investigated in a mixed sclerophyll–rainforest ecosystem in the Nightcap Range, North Coast, New South Wales. Aims To examine rates of seedling recruitment and resprouting in functional and phytogeographic components of wet sclerophyll forest (WSRf), and adjacent open forest (OF) and rock outcrop shrubland (RO). Methods Species resprouting and seedling recruitment traits (fire responses) were recorded in 45 stem plots and 225 seedling subplots in WSRf, OF and RO. Species fire responses were classified, community fire-response spectra compiled and rates of seedling recruitment and resprouting in WSRf examined in relation to primary fire response, growth-form, habitat and broad functional and phytogeographic species groupings. Species size-regenerative class distribution was used to analyse population structure, fire impact, regeneration and recruitment in resprouter species that comprised most of the mesic-Gondwanan element of the WSRf flora. Key results WSRf, OF and RO habitats had distinctively different fire-response spectra. In WSRf, there was a high proportion of mesophyll resprouter species of Gondwanan origin with nil or very low seedling recruitment, a distinct component of mesophyll seeders of Indo-Malayan origin, as well as sclerophyll seeders and resprouters that also comprised most of the OF and RO floras. Resprouters comprised 75% of the WSRf flora, 50% OF and 10% pavement shrubland. Continuous size-class distributions indicated recruitment between fire events in the majority of mesophyll resprouters in WSRf. Lower total seedling density appeared to reflect inherent species traits and less canopy disturbance by fire. Large sclerophyll species forming the unburnt canopy of WSRf had very low seedling recruitment. Conclusions Different habitats (WSRf, OF and RO) and functional and phytogeographic clades in WSRf display distinctive patterns of resprouting and seedling-recruitment fire response. Fire responses of species that maintain species population and community composition are governed by fire regime, habitat variables and inherent species traits. Implications The distinctive fire-response spectrum of WSRf appears to be a direct consequence of the overlap of ‘new’ and ‘old’ floras in this broad vegetation type.
... In Australia, few TM rainforest species have been studied directly to determine their responses to drying and freezing, however, some data are available for related species. A recent study of 162 Australian subtropical and temperate rainforest species (including 58 species with a distribution that extended to TMCF and 44 species from genera that occur in TMCF), found the proportion of recalcitrant tree species to be high at 42% (Sommerville et al., 2021). However, compared to tree species, the seeds of shrubs and herbs were much Table 1 Seed storage behaviour of 28 target Australian TMCF species: Genera containing target Australian TMCF species for which seed storage behaviour of one or more related species is known. ...
... Storage behaviour is categorised as: Orthodox: tolerant of drying and freezing (O), Intermediate: partially tolerant of drying and freezing (I) and Recalcitrant: sensitive to drying (R). This is a subset of a much larger more likely to be desiccation tolerant (Sommerville et al., 2021). reported that the storage behaviour of an untested species can often be predicted by that of other species in the same genus. ...
... On that basis, research is needed into the storage behaviour of 168 previously unstudied Australian TM genera, including 68 genera for which only 1 or 2 species have been studied to date (excluding mono-and bispecific genera). However, caution is required in using genus as a surrogate to determine storage behaviour unless several species with similar seed structure to the untested species have shown a consistent response (Sommerville et al., 2021). Wide differences in storage behaviour can occur among species in the same genus (Subbiah et al., 2019), particularly when those species have seeds with a different structure but also sometimes when they do not (Sommerville et al., 2021). ...
... In addition, the innovative techniques and analyses generated by EMCRs at the seed science conference may play a critical role in global initiatives relating to the UN Decade of Restoration (https://www.decadeonrestoration. org/about-un-decade), and in solving the global food crisis. The UN Decade of Restoration aims to restore degraded and deforested lands, which will require the use of highquality seeds, for which seed storage, seed dormancy and environmental conditions to support germination of many species remain unresolved (Sommerville et al. 2021;Collette et al. 2022;Dalziell et al. 2022). Similarly, the global food crisis requires an understanding into best-practice seed processing and storage methodologies; generating seeds that are climate resilient; and producing high crop productivity and yield to improve food security (Dalziell and Tomlinson 2017;De Vitis et al. 2020;Leger et al. 2021). ...
Seed science is a vital field of research that contributes to many areas of knowledge in fundamental ecology and evolution, as well as in applied areas of food production, and the conservation and restoration of native plants. A large amount of novel information, technologies and processes in seed science research are being produced and developed by early to middle career researchers (EMCRs) in academic, government and private science sectors. This breadth and novelty of research by EMCRs was evident at the second Australasian Seed Science Conference held online in September 2021. EMCRs represented almost one-third of the presenting delegates at the conference and covered research in areas including functional seed trait relationships, responses of seed traits and germination to environmental change, managing seeds in ex-situ seed and germplasm collections and using seeds as food sources. As future environmental, social and economic challenges arise, EMCR seed scientists will be at the forefront of emerging fundamental ecological and evolutionary seed science knowledge, as well as the development of technologies and processes for the conservation of native species, the utilisation of seeds in agriculture and food production, and many new ideas yet to be discovered.
... Seed banking may be used to conserve any species producing seeds that tolerate drying and storage at low temperatures, criteria that apply to an estimated 92% of seed-producing species (Wyse and Dickie 2017). Although rainforest environments are known to have a higher proportion of species producing seeds intolerant of drying than other habitats (Tweddle et al. 2003), recent research on 162 Australian rainforest species demonstrated that 74% were fully, or at least partially, tolerant of the drying required for conventional seed banking and 50% were also tolerant of storage at −20°C (Sommerville et al. 2021). These results suggested that seed banking may be more feasible for conserving rainforest species than previously expected. ...
... In this study, we used artificial aging to estimate the comparative longevity in storage of 33 rainforest species with likely orthodox seed storage behaviour (Sommerville et al. 2021). We compared longevity to habit, habitat range, seed characteristics (endospermy and dry weight), and environmental variables in the collection habitat (such as precipitation, average temperature and elevation) to determine which factors had the greatest influence on seed longevity. ...
Context. Fifty per cent of Australian rainforest species produce orthodox seeds, but little is known about their longevity in storage. Aims. To (1) estimate the longevity of seeds of 33 rainforest species using artificial aging; (2) assess the influence of habit, habitat range (restricted to rainforest or more broadly distributed), seed characteristics (endospermy, dry weight), and collection environment (e.g. precipitation, elevation and average temperature) on longevity; (3) compare longevity of rainforest seeds to previously assessed species from non-rainforest habitats; (4) compare longevity in artificial aging to real-time longevity in storage. Methods. Seeds were aged at 60% relative humidity and 45°C, and tested at predetermined intervals until germination was reduced to zero. The time taken for germination to decline to 50% (p 50AA) was calculated by probit analysis. Ordinary least-squares regression was used to model p 50AA for rainforest and non-rainforest species against predictor variables. Values for p 50AA were then compared with the actual longevity in storage at −20°C (p 50RT) using Pearson's correlation. Key results. Species restricted to rainforest exhibited a significantly lower p 50AA than species with a wider distribution or those restricted to non-rainforest habitats. Collection elevation had a significant negative influence on p 50AA. In all, 14 of 33 species showed a significant decline in viability after ≤12 years in storage. Values of p 50AA were not correlated with p 50RT. Conclusions. Rainforests contain a high proportion of potentially, and actually, short-lived species; however, p 50AA is not a good predictor of their real-time longevity. Implications. Rainforest species should be managed as short-lived, with viability checked at least every 5 years, until real-time longevity data indicate otherwise.
... Seed with intermediate storage physiology can display tolerance to desiccation, but sensitivity to freezing [12,23]. To test for freezing sensitivity, L. bullata and L. obcordata seed desiccated to 30% eRH and 15% eRH were exposed to 5 • C, −18 • C, and −196 • C for 14 days. ...
There is no published information on the seed germination or seed storage physiology of Lophomyrtus bullata, Lophomyrtus obcordata, and Neomyrtus pedunculata. This lack of information is hampering conservation efforts of these critically endangered species. This study investigated the seed morphology, seed germination requirements, and long-term seed storage methods for all three species. The impact of desiccation, desiccation and freezing, as well as desiccation plus storage at 5 °C, −18 °C, and −196 °C on seed viability (germination) and seedling vigour was assessed. Fatty acid profiles were compared between L. obcordata and L. bullata. Variability in storage behaviour between the three species was investigated through differential scanning calorimetry (DSC) by comparing thermal properties of lipids. L. obcordata seed were desiccation-tolerant and viability was retained when desiccated seed was stored for 24 months at 5 °C. L. bullata seed was both desiccation- and freezing-sensitive, while N. pedunculata was desiccation-sensitive. DSC analysis revealed that lipid crystallisation in L. bullata occurred between −18 °C and −49 °C and between −23 °C and −52 °C in L. obcordata and N. pedunculata. It is postulated that the metastable lipid phase, which coincides with the conventional seed banking temperature (i.e., storing seeds at −20 ± 4 °C and 15 ± 3% RH), could cause the seeds to age more rapidly through lipid peroxidation. Seeds of L. bullata, L. obcordata and N. pedunculata are best stored outside of their lipid metastable temperature ranges.
... Desiccation-sensitive seeds are mainly limited to climax species and/or to habitats where they are not likely to be exposed to drying and/or freezing conditions after dispersal (Tweddle et al., 2003), such as in tropical rainforests. However, seed desiccation sensitivity is a relatively understudied trait, particularly for species from tropical montane forests (Tweddle et al., 2003;Sommerville et al., 2021). We show below how this lack of tropical data could reduce the predictive power of global models. ...
... For example, in a review of South Pacific rainforest species, data on desiccation and cold storage tolerance were lacking for more than half of the 1503 genera examined (Sommerville et al., 2018). This paucity of information for tropical and subtropical rainforest species hinders their long-term conservation through conventional seed banking (Sommerville et al., 2021). Hong and Ellis (1996) developed a protocol to evaluate seed storage behaviour, by assessing seed germination before and after drying. ...
... To reduce the number of seeds needed, Pritchard et al. (2004) developed a screening approach for species from the family Arecaceae (the '100-seed test'), which was then adapted to assess different floras worldwide (e.g. Hamilton et al., 2013;Gold and Hay, 2014;Lan et al., 2014;Mattana et al., 2020;Sommerville et al., 2021). Mattana et al. (2020) compared the gathering of new experimental data through an adaptation of the '100-seed test' and seed trait models (Lan et al., 2014), with global predictions of species seed desiccation likelihood , in order to assess the seed desiccation tolerance of native trees from the Dominican Republic (a Caribbean island). ...
Background
Plant seeds have many traits that influence ecological functions, ex situ conservation, restoration success and their sustainable use. Several seed traits are already known to vary significantly between tropical and temperate regions. Here we present three additional traits for which existing data indicate differences between geographical zones. We discuss evidence for geographical bias in availability of data for these traits, as well as negative consequences of this bias.
Scope
We reviewed the literature on seed desiccation sensitivity studies that compare predictive models to experimental data and show how a lack of data on populations and species from tropical regions could reduce the predictive power of global models. In addition, we compiled existing data on relative embryo size and post-dispersal embryo growth and found that relative embryo size was significantly larger, and embryo growth limited, in tropical species. The available data showed strong biases towards non-tropical species and certain families, indicating that these need to be corrected to perform truly global analyses. Furthermore, we argue that the low number of seed germination studies on tropical high-mountain species makes it difficult to compare across geographical regions and predict the effects of climate change in these highly specialized tropical ecosystems. In particular, we show that seed traits of geographically restricted páramo species are studied less than those more widely distributed, with most publications unavailable in English or in the peer-reviewed literature.
Conclusions
The low availability of functional seed trait data from populations and species in the tropics can have negative consequences for macroecological studies, predictive models and their application in plant conservation. We propose that global analyses of seed traits with evidence for geographical variation prioritise generation of new data from tropical regions as well as multi-lingual searches of both grey- and peer-reviewed literature in order to fill geographical and taxonomical gaps.
... Difficulty propagating plants from seed because of dormancy is also a critical problem in restoration and reintroduction of plant species (Cochrane et al. 2002). For seed-banking purposes, the issue of poor germination can now be avoided by applying a key to storage behaviour that is based on seed characteristics rather than germination (Sommerville et al. 2021). However, the ultimate use of banked seeds usually involves germination, whether the seeds are used for propagation, research, or long-term monitoring. ...
Context Seed dormancy is one issue hindering implementation of conservation actions for rainforest species. Aims We studied dormancy and germination in Tasmannia sp. Mt Bellenden Ker and Tasmannia membranea, two tropical montane rainforest species threatened by climate change, to develop a better understanding of dormancy in the species and the genus. Methods Dormancy was classified for T. sp. Mt Bellenden Ker on the basis of an imbibition test, analysis of embryo to seed length (E:S) ratios and germination in response to the following four dormancy-breaking treatments: (1) scarification of the seedcoat near the micropylar end; (2) removal of the seedcoat; (3) application of 100 mg L−1 or (4) 500 mg L−1 gibberellic acid. The most effective treatment was then tested on T. membranea. The requirement for light for germination was also assessed. Key results Both scarified and intact seeds imbibed water. Initial E:S ratios were <0.22 for both species and increased up to 0.74 after 40 days, just before radicle emergence, for T. sp. Mt Bellenden Ker. Germination proportions were significantly higher in Treatments 1 and 2 than the remaining treatments for T. sp. Mt Bellenden Ker; T. membranea responded similarly well to Treatment 1. Germination under alternating light/dark conditions was slightly, but not significantly, greater than germination in the dark alone. Conclusions Both species have morphophysiological dormancy and treatments that remove seedcoat resistance to embryo growth facilitate germination. These treatments may improve germination in other species from the genus Tasmannia. Implications This knowledge will aid the germination of seeds to implement conservation strategies for Tasmannia spp.
... The remainder of the family falls into the category of 'exceptional' [74], with species that no longer produce seeds due to myrtle rust (e.g., Rhodamnia rubescens and Rhodomyrtus psidioides [70,75]), or that produce seeds that are intolerant of desiccation (e.g., Syzygium spp. [72,76]) or storage at −20 • C (e.g., Backhousia citriodora [77] and Rhodamnia maideniana [78]). ...
... Although the majority of Myrtaceae species have dry fruit and orthodox seeds, fleshy fruited trees and shrubs are common in the Myrteae and Syzygieae tribes [1] and these are more likely to have desiccation sensitive seeds than those with dry fruits [11]. A study of Australian species has found this to be true for fleshy-fruited species containing a single seed, however those containing a number of small seeds were more likely to show intermediate behaviors, with typically desiccation tolerant seeds but a range of responses to freezing [78]. As repeated infections of reproductive organs by myrtle rust are likely to affect seed set [81], even species with orthodox seed storage behavior may become exceptional species, resulting in the need for alternate conservation methods such as tissue culture and cryopreservation for a greater proportion of species. ...
... Syzygium species typically have fleshy fruits with desiccation sensitive seeds [72] however there is some variation within the genus. For example, S. paniculatum and S. unipunctatum have desiccation sensitive seeds [78] while S. anisatum fruits are dry and their seeds are orthodox, though artificial aging experiments have shown they are likely to be very shortlived in storage at −20 • C [106]. S. anisatum is the only species of the genus with seeds held in storage at the Australian PlantBank [73]. ...
The Myrtaceae is a very large and diverse family containing a number of economically and ecologically valuable species. In Australia, the family contains approximately 1700 species from 70 genera and is structurally and floristically dominant in many diverse ecosystems. In addition to threats from habitat fragmentation and increasing rates of natural disasters, infection by myrtle rust caused by Austropuccinia psidii is of significant concern to Australian Myrtaceae species. Repeated infections of new growth have caused host death and suppressed host populations by preventing seed set. Although most Myrtaceae species demonstrate orthodox seed storage behavior, exceptional species such as those with desiccation sensitive seed or from myrtle rust-suppressed populations require alternate conservation strategies such as those offered by cryobiotechnology. Targeting seven key Australian genera, we reviewed the available literature for examples of cryobiotechnology utilized for conservation of Myrtaceae. While there were only limited examples of successful cryopreservation for a few genera in this family, successful cryopreservation of both shoot tips and embryonic axes suggest that cryobiotechnology provides a viable alternative for the conservation of exceptional species and a potential safe storage method for the many Myrtaceae species under threat from A. psidii.
... A major step forward is that requirements to conserve these species ex situ are being progressively understood and workflows have been developed to assist the fast-tracking of conservation efforts. This includes the latest techniques for selection of appropriate germplasm to conserve ex situ, an important step for the success of ex situ conservation of 'exceptional species' which require significant research effort [49]. At the regional level, the European Native Seed Conservation Network (ENSCONET), a consor-tium of organisations interested in native species conservation, created seed collecting and processing manuals for practitioners, available in nine European languages [50,51]. ...
... Efforts have largely focused on dryland species, due to the expectation of desiccation sensitivity of seeds of rainforest. Several studies have explored the seed storage potential of Australian rainforest flora [49,94] and these results were combined with other data sets to develop a key for determining the seed storage potential of untested rainforest species [49]. This key will help us to understand the complex biology of 'exceptional species' and recognise species that need conservation efforts beyond the traditional seed bank. ...
... Efforts have largely focused on dryland species, due to the expectation of desiccation sensitivity of seeds of rainforest. Several studies have explored the seed storage potential of Australian rainforest flora [49,94] and these results were combined with other data sets to develop a key for determining the seed storage potential of untested rainforest species [49]. This key will help us to understand the complex biology of 'exceptional species' and recognise species that need conservation efforts beyond the traditional seed bank. ...
There is a pressing need to conserve plant diversity to prevent extinctions and to enable sustainable use of plant material by current and future generations. Here, we review the contribution that living collections and seed banks based in botanic gardens around the world make to wild plant conservation and to tackling global challenges. We focus in particular on the work of Botanic Gardens Conservation International and the Millennium Seed Bank of the Royal Botanic Gardens, Kew, with its associated global Partnership. The advantages and limitations of conservation of plant diversity as both living material and seed collections are reviewed, and the need for additional research and conservation measures, such as cryopreservation, to enable the long-term conservation of ‘exceptional species’ is discussed. We highlight the importance of networks and sharing access to data and plant material. The skill sets found within botanic gardens and seed banks complement each other and enable the development of integrated conservation (linking in situ and ex situ efforts). Using a number of case studies we demonstrate how botanic gardens and seed banks support integrated conservation and research for agriculture and food security, restoration and reforestation, as well as supporting local livelihoods.
