Summary Trait‐based approaches have improved our understanding of plant evolution, community assembly and ecosystem functioning. A major challenge for the upcoming decades is to understand the functions and evolution of early life‐history traits, across levels of organization and ecological strategies. Although a variety of seed traits are critical for dispersal, persistence, germination timing and seedling establishment, only seed mass has been considered systematically. Here we suggest broadening the range of morphological, physiological and biochemical seed traits to add new understanding on plant niches, population dynamics and community assembly. The diversity of seed traits and functions provides an important challenge that will require international collaboration in three areas of research. First, we present a conceptual framework for a seed ecological spectrum that builds upon current understanding of plant niches. We then lay the foundation for a seed‐trait functional network, the establishment of which will underpin and facilitate trait‐based inferences. Finally, we anticipate novel insights and challenges associated with incorporating diverse seed traits into predictive evolutionary ecology, community ecology and applied ecology. If the community invests in standardized seed‐trait collection and the implementation of rigorous databases, major strides can be made at this exciting frontier of functional ecology.

Summary Assumptions about the germination ecology of alpine plants are presently based on individual species and local studies. A current challenge is to synthesise, at the global level, the alpine seed ecological spectrum. We performed a meta‐analysis of primary data from laboratory experiments conducted across four continents (excluding the tropics) and 661 species, to estimate the influence of six environmental cues on germination proportion, mean germination time and germination synchrony; accounting for seed morphology (mass, embryo : seed ratio) and phylogeny. Most alpine plants show physiological seed dormancy, a strong need for cold stratification, warm‐cued germination and positive germination responses to light and alternating temperatures. Species restricted to the alpine belt have a higher preference for warm temperatures and a stronger response to cold stratification than species whose distribution extends also below the treeline. Seed mass, embryo size and phylogeny have strong constraining effects on germination responses to the environment. Globally, overwintering and warm temperatures are key drivers of germination in alpine habitats. The interplay between germination physiology and seed morphological traits further reflects pressures to avoid frost or drought stress. Our results indicate the convergence, at the global level, of the seed germination patterns of alpine species.

An alarming proportion of Australia’s unique plant biodiversity is under siege from a variety of environmental threats. Options for in situ conservation are becoming increasingly compromised as encroaching land use, climate change and introduced diseases are highly likely to erode sanctuaries regardless of best intentions. Ex situ conservation is currently limited to botanic garden living collections and seed banking, with in vitro and cryopreservation technologies still being developed to address ex situ conservation of species not amenable to conventional storage. Cryopreservation (storage in liquid nitrogen) has been used successfully for long-term biosecure storage of shoot tips of several species of threatened Australian plants. We present a case for building on this research and fostering further development and utilisation of cryopreservation as the best means of capturing critical germplasm collections of Australian species with special storage requirements (e.g. recalcitrant-seeded taxa and species with short-lived seeds) that currently cannot be preserved effectively by other means. This review highlights the major issues in cryopreservation that can limit survival including ice crystal damage and desiccation, toxicity of cryoprotective agents, membrane damage, oxidative stress and mitochondrial function. Progress in understanding and mitigating these stresses is vital for advancing cryopreservation for conservation purposes.

Premise of research. Orchids are among the most enigmatic of plant species. Yet the Orchidaceae comprises more species at risk of extinction than any other plant family. The collection and storage of orchid germplasmprincipally seeds and associated mycorrhizal fungi but also protocorm-like bodies using encapsulation and vitrification techniques-allows for secure ex situ conservation. This article reviews the approaches and techniques used for the ex situ conservation of orchid germplasm, with a focus on seed banking and the use of cryopreservation techniques to improve the longevity of germplasm.Pivotal results. It is increasingly apparent that cryopreservation-the storage of germplasm at ultra-low temperatures (e.g., in liquid nitrogen)-is required for the long-term and low-maintenance conservation of all types of orchid germplasm. For orchid seeds, desiccation tolerance is common, but longevity in storage is poor. Cryopreservation of orchid seeds shows promise, but some complexities in low-temperature storage behavior still require explanation and resolution. The application of more advanced cryopreservation techniques, including encapsulation-dehydration and vitrification, is becoming increasingly common. These techniques provide for the simultaneous storage of orchid propagules with their compatible fungus, while for seeds, vitrification techniques show potential for improving tolerance to the stresses of cryopreservation. Conclusions.A renewed focus on describing the low-temperature storage physiology of orchid seeds to more precisely define the relationship between seed water content, storage temperature, and seed survival is required, as is perhaps the wider adoption of the use of cryoprotectants for seeds. This research, coupled with the development of improved methods of seed viability testing, will support the growing work of germplasm banks to protect orchid biodiversity in the face of habitat loss and potential species extinction.

This study investigates patterns of genetic connectivity among 11 co-distributed tropical rainforest tree species from the genus Elaeocarpus across a biogeographic barrier, the Black Mountain Corridor (BMC) in the Australian Wet Tropics (AWT). We analysed a combination of allelic and flanking region sequence data from microsatellite markers, and evaluated the relative influence of environmental preferences and functional traits on genetic diversity and gene flow. The results indicate that only in three species geographic structuring of haplotype distribution reflects a north vs. south of the BMC pattern. Environmental factors linked with altitude were recognized as affecting genetic trends, but the selective processes operating on upland species appear to be associated with competitiveness and regeneration opportunities on poor soil types rather than climate variables alone. In contrast to previous observations within southeastern Australian rainforests, genetic differentiation in the AWT appears to be associated with small-fruited rather than large-fruited species, highlighting how external factors can influence the dispersal dimension. Overall, this study emphasizes the importance of considering functional and environmental factors when attempting generalizations on landscape-level patterns of genetic variation. Understanding how plant functional groups respond to environmental and climatic heterogeneity can help us predict responses to future change.

Ex situ conservation of threatened terrestrial orchids requires the simultaneous conservation of their mycorrhizal associations. A method for encapsulating both seed and fungi in alginate beads (known as encapsulation–dehydration) was applied to the storage and propagation of two endangered orchid species in NSW, Australia—Pterostylis saxicola D.L.Jones & M.A.Clem. and Diuris arenaria D.L.Jones. We tested the effect of storage duration and temperature on fungal recovery and germination potential in vitro, and recorded survival for seedlings subsequently transferred to potting mix. Storage at 23°C significantly reduced fungal recovery and germination for both species after only 3 months (P < 0.05), whereas storage at 4°C significantly reduced fungal recovery for P. saxicola after 6 months (P < 0.05). Storage for 6 months at −18 and −196°C had no significant effect on the fungal recovery and germination percentages of either species. All beads transferred directly from in vitro culture to potting mix resulted in the establishment of at least one seedling, and production of a healthy tuberoid, when transferred near the commencement of the natural growing season. The encapsulation–dehydration method may have a practical application for use in ex situ conservation of other terrestrial orchids, as well as their mycorrhizal fungi.

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 desiccation responses to environmental, habit, fruit and seed characteristics to identify the most useful predictors of desiccation sensitivity. Of 162 species with ≥ 50% initial germination, 22% were sensitive to desiccation, 64% were tolerant and 10% were partially tolerant; the responses of 4% were uncertain. Of 107 desiccation tolerant species tested for response to freezing, 24% were freezing sensitive or short-lived in storage at −20 °C. Median values for fresh seed moisture content (SMC), oven dry weight (DW) and the likelihood of desiccation sensitivity (PD-S) were significantly greater for desiccation sensitive than desiccation tolerant seeds. Ninety-four to 97% of seeds with SMC < 29%, DW < 20 mg or PD-S < 0.01 were desiccation tolerant. Ordinal logistic regression of desiccation response against environmental, habit, fruit and seed characteristics indicated that the likelihood of desiccation sensitivity was significantly increased by a tree habit, fleshy fruit, increasing fresh SMC and increasing PD-S. The responses observed in this study were combined with earlier studies to develop a simple decision key to aid prediction of desiccation responses in untested rainforest species.

Abstract. Rainforests in the South Pacific hold a considerable amount of plant diversity, with rates of species endemism >80% in some countries. This diversity is rapidly disappearing under pressure from logging, clearing for agriculture or mining, introduced pests and diseases and other anthropogenic sources. Ex situ conservation techniques offer a means to limit the loss of plant diversity. Seed banking is considered the most efficient and cost effective of these techniques but is applicable only to seed capable of tolerating desiccation and cold storage. Data on the degree of tolerance of these conditions was lacking for more than half of the 1503 South Pacific rainforest genera examined for this review. Of the 710 genera for which data were available, the storage behaviour of 324 was based on an assessment of only one or two species, although 76% of those genera contained at least 10 species. Many of the unstudied or poorly studied genera are shared across several South Pacific nations, providing an excellent opportunity for collaboration on future ex situ research and conservation. 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. Seed banking could therefore provide a suitable means for preserving a large proportion of the rainforest flora before it becomes extinct in the wild. Alternatives for preserving species that are not suitable for seed banking are also discussed.