Towards a More Efficient In and Ex Situ Conservation of Sri Lankan Wild Rice Species.

Five species of wild Oryza (O. nivara, O. rufipogon, O. eichengeri, O. rhizomatis and O. granulata), including the endemic species O. rhizomatis, have been recorded in Sri Lanka. These species are facing continuous decline in their populations due to natural and anthropogenic processes, with habitat loss being the main threat. This study aimed to provide information on the distribution, the current status of ex situ and in situ conservation, and to identify high-priority species and sites of wild rice in Sri Lanka, in order to improve the effectiveness of conservation efforts. Occurrence records of Sri Lankan wild rice species were collected from literature, gene banks, and field surveys. The distribution of these species was mapped, and areas with high species richness were identified. A gap analysis was conducted to determine the high-priority areas and species for ex situ and in situ conservation. It was found that about 23% of the wild rice populations in Sri Lanka were within protected areas, and by expanding these protected areas by 1 km, an additional 22% of the populations located on the border of these areas could be effectively conserved. Our analysis also revealed that 62% of Sri Lankan wild rice populations were not represented in gene banks. The species-rich areas were found to be in only two districts (Polonnaruwa and Monaragala), and less than 50% of these areas were within protected areas. Based on these findings, O. rhizomatis, O. eichengeri, and O. rufipogon were identified as high-priority species for in situ conservation. Ex situ collections were also deemed necessary for O. granulata and O. rhizomatis to ensure diversity representation in gene banks.

Selecting the best candidates for resurrecting extinct-in-the-wild plants from herbaria.

Resurrecting extinct species is a fascinating and challenging idea for scientists and the general public. Whereas some theoretical progress has been made for animals, the resurrection of extinct plants (de-extinction sensu lato) is a relatively recently discussed topic. In this context, the term 'de-extinction' is used sensu lato to refer to the resurrection of 'extinct in the wild' species from seeds or tissues preserved in herbaria, as we acknowledge the current impossibility of knowing a priori whether a herbarium seed is alive and can germinate. In plants, this could be achieved by germinating or in vitro tissue-culturing old diaspores such as seeds or spores available in herbarium specimens. This paper reports the first list of plant de-extinction candidates based on the actual availability of seeds in herbarium specimens of globally extinct plants. We reviewed globally extinct seed plants using online resources and additional literature on national red lists, resulting in a list of 361 extinct taxa. We then proposed a method of prioritizing candidates for seed-plant de-extinction from diaspores found in herbarium specimens and complemented this with a phylogenetic approach to identify species that may maximize evolutionarily distinct features. Finally, combining data on seed storage behaviour and longevity, as well as specimen age in the novel 'best de-extinction candidate' score (DEXSCO), we identified 556 herbarium specimens belonging to 161 extinct species with available seeds. We expect that this list of de-extinction candidates and the novel approach to rank them will boost research efforts towards the first-ever plant de-extinction.

Recruitment Traits Could Influence Species' Geographical Range: A Case Study in the Genus Saxifraga L.

The reasons why some species occur widespread, while related species have restricted geographical ranges have been attributed to habitat specialization or ecological niche breadth. For species in the genus Saxifraga, habitat specialization alone cannot explain the distributional differences observed. We hypothesize that recruitment traits (i.e., germination, emergence, and survival) may account for differences in geographical ranges and that early life stages correlate to survival. We studied recruitment responses in 13 widespread and 12 narrow-ranged Saxifraga species in the laboratory and common garden experiments using seeds collected from 79 populations in the European Alps. We found that in the laboratory cold temperature led to higher germination percentages compared with warm temperature for both distribution groups. This represents an exception to the general assumption that alpine species require warm cues for germination. In warm laboratory temperatures, widespread species germinated better than narrow-ranged species, indicating a greater tolerance of warm temperatures for the former. Subsequent to germination, recruitment traits between the two distribution groups were lower or null in the common garden, suggesting that the impact of recruitment on species' geographical ranges occurs at the earliest life stage. Mean time to emergence of narrow-ranged species showed lower variability than that of widespread species. Consistently, intraspecific variation of mean annual temperatures between seed collection sites was lower for narrow-ranged species, indicating a close relationship between home sites and emergence time. Emergence percentage was a strong predictor of survival only for widespread species, underlining that seed and seedling functional traits differ between distribution groups, which require further research. Our results support the view that early life stages are critical to population dynamics and thus can influence species' geographical ranges. The wider responses to climatic conditions in widespread species may have facilitated their spread across the Alps. Our results also suggest that all Saxifraga species face a considerable threat from climate warming due to their overall cold-adapted recruitment niche.

The seed germination spectrum of alpine plants: a global meta-analysis.

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.

Ex situ collections and their potential for the restoration of extinct plants.

The alarming current and predicted species extinction rates have galvanized conservationists in their efforts to avoid future biodiversity losses, but for species extinct in the wild, few options exist. We posed the questions, can these species be restored, and, if so, what role can ex situ plant collections (i.e., botanic gardens, germplasm banks, herbaria) play in the recovery of plant genetic diversity? We reviewed the relevant literature to assess the feasibility of recovering lost plant genetic diversity with using ex situ material and the probability of survival of subsequent translocations. Thirteen attempts to recover species extinct in the wild were found, most of which used material preserved in botanic gardens (12) and seed banks (2). One case of a locally extirpated population was recovered from herbarium material. Eight (60%) of these cases were successful or partially successful translocations of the focal species or population; the other 5 failed or it was too early to determine the outcome. Limiting factors of the use of ex situ source material for the restoration of plant genetic diversity in the wild include the scarcity of source material, low viability and reduced longevity of the material, low genetic variation, lack of evolution (especially for material stored in germplasm banks and herbaria), and socioeconomic factors. However, modern collecting practices present opportunities for plant conservation, such as improved collecting protocols and improved cultivation and storage conditions. Our findings suggest that all types of ex situ collections may contribute effectively to plant species conservation if their use is informed by a thorough understanding of the aforementioned problems. We conclude that the recovery of plant species currently classified as extinct in the wild is not 100% successful, and the possibility of successful reintroduction should not be used to justify insufficient in situ conservation.

Colecciones Ex Situ y su Potencial para la Restauración de Plantas Extintas Resumen Las alarmantes tasas de extinción actuales y pronosticadas han incitado a los conservacionistas a esforzarse para evitar las futuras pérdidas de biodiversidad, pero para las especies que ya se encuentran extintas en vida silvestre existen pocas opciones. Nos preguntamos si estas especies pueden ser restauradas, y de ser así, qué papel pueden desempeñar las colecciones ex situ de plantas (es decir, jardines botánicos, bancos de germoplasma, herbarios) en la recuperación de la diversidad genética de las plantas. Revisamos la literatura relevante para evaluar la factibilidad de la recuperación de la diversidad genética perdida y la probabilidad de supervivencia subsecuente de las reubicaciones. Encontramos 13 intentos por recuperar especies extintas en vida silvestre, la mayoría de los cuales usó material preservado en jardines botánicos (12) y en bancos de semillas (2). También hubo un caso de una población eliminada localmente que fue recuperada con material de un herbario. Ocho (60%) de estos casos fueron reubicaciones exitosas o parcialmente exitosas de la especie o población focal; los otros cinco fallaron o era demasiado pronto para poder determinar el resultado. Los factores que limitan el uso de material proveniente de colecciones ex situ para la restauración de la diversidad genética de las plantas en vida silvestre incluyen la escasez de material original, la baja viabilidad y la longevidad reducida del material, la baja variación genética, la falta de evolución (especialmente para el material almacenado en herbarios y bancos de germoplasma) y los factores socioeconómicos. A pesar de esto, las prácticas modernas de colección representan una oportunidad para la conservación de las plantas, como los protocolos mejorados de recolección y las condiciones acrecentadas de cultivo y almacenamiento. Nuestros hallazgos sugieren que todos los tipos de colecciones ex situ pueden contribuir efectivamente a la conservación de especies de plantas si su uso está respaldado por un entendimiento a fondo de los problemas antes mencionados. Concluimos que la recuperación de especies de plantas que actualmente están clasificadas como extintas en vida silvestre no es 100% exitosa y que la posibilidad de una reintroducción exitosa no debería utilizarse para justificar una conservación in situ insuficiente.

Habitat-related seed germination traits in alpine habitats.

Understanding the key aspects of plant regeneration from seeds is crucial in assessing species assembly to their habitats. However, the regenerative traits of seed dormancy and germination are underrepresented in this context. In the alpine zone, the large species and microhabitat diversity provide an ideal context to assess habitat-related regenerative strategies. To this end, seeds of 53 species growing in alpine siliceous and calcareous habitats (6230 and 6170 of EU Directive 92/43, respectively) were exposed to different temperature treatments under controlled laboratory conditions. Germination strategies in each habitat were identified by clustering with k-means. Then, phylogenetic least squares correlations (PGLS) were fitted to assess germination and dormancy differences between species' main habitat (calcareous and siliceous), microhabitat (grasslands, heaths, rocky, and species with no specific microhabitats), and chorology (arctic-alpine and continental). Calcareous and siliceous grasslands significantly differ in their germination behaviour with a slow, mostly overwinter germination and high germination under all conditions, respectively. Species with high overwinter germination occurs mostly in heaths and have an arctic-alpine distribution. Meanwhile, species with low or high germinability in general inhabit in grasslands or have no specific microhabitat (they belong to generalist), respectively. Alpine species use different germination strategies depending on habitat provenance, species' main microhabitat, and chorotype. Such differences may reflect adaptations to local environmental conditions and highlight the functional role of germination and dormancy in community ecology.

Seed dormancy and germination changes of snowbed species under climate warming: the role of pre- and post-dispersal temperatures.

BACKGROUND AND AIMS: Climate warming has major impacts on seed germination of several alpine species, hence on their regeneration capacity. Most studies have investigated the effects of warming after seed dispersal, and little is known about the effects a warmer parental environment may have on germination and dormancy of the seed progeny. Nevertheless, temperatures during seed development and maturation could alter the state of dormancy, affecting the timing of emergence and seedling survival. Here, the interplay between pre- and post-dispersal temperatures driving seed dormancy release and germination requirements of alpine plants were investigated. METHODS: Three plant species inhabiting alpine snowbeds were exposed to an artificial warming treatment (i.e. +1·5 K) and to natural conditions in the field. Seeds produced were exposed to six different periods of cold stratification (0, 2, 4, 8, 12 and 20 weeks at 0 °C), followed by four incubation temperatures (5, 10, 15 and 20 °C) for germination testing. KEY RESULTS: A warmer parental environment produced either no or a significant increase in germination, depending on the duration of cold stratification, incubation temperatures and their interaction. In contrast, the speed of germination was less sensitive to changes in the parental environment. Moreover, the effects of warming appeared to be linked to the level of (physiological) seed dormancy, with deeper dormant species showing major changes in response to incubation temperatures and less dormant species in response to cold stratification periods. CONCLUSIONS: Plants developed under warmer climates will produce seeds with changed germination responses to temperature and/or cold stratification, but the extent of these changes across species could be driven by seed dormancy traits. Transgenerational plastic adjustments of seed germination and dormancy shown here may result from increased seed viability, reduced primary and secondary dormancy state, or both, and may play a crucial role in future plant adaptation to climate change.

Climate warming could increase recruitment success in glacier foreland plants.

BACKGROUND AND AIMS: Glacier foreland plants are highly threatened by global warming. Regeneration from seeds on deglaciated terrain will be crucial for successful migration and survival of these species, and hence a better understanding of the impacts of climate change on seedling recruitment is urgently needed to predict future plant persistence in these environments. This study presents the first field evidence of the impact of climate change on recruitment success of glacier foreland plants. METHODS: Seeds of eight foreland species were sown on a foreland site at 2500 m a.s.l., and at a site 400 m lower in altitude to simulate a 2·7 °C increase in mean annual temperature. Soil from the site of origin was used to reproduce the natural germination substrate. Recruitment success, temperature and water potential were monitored for 2 years. The response of seed germination to warming was further investigated in the laboratory. KEY RESULTS: At the glacier foreland site, seedling emergence was low (0 to approx. 40 %) and occurred in summer in all species after seeds had experienced autumn and winter seasons. However, at the warmer site there was a shift from summer to autumn emergence in two species and a significant increase of summer emergence (13-35 % higher) in all species except two. Survival and establishment was possible for 60-75 % of autumn-emerged seedlings and was generally greater under warmer conditions. Early snowmelt in spring caused the main ecological factors enhancing the recruitment success. CONCLUSIONS: The results suggest that warming will influence the recruitment of glacier foreland species primarily via the extension of the snow-free period in spring, which increases seedling establishment and results in a greater resistance to summer drought and winter extremes. The changes in recruitment success observed here imply that range shifts or changes in abundance are possible in a future warmer climate, but overall success may be dependent on interactions with shifts in other components of the plant community.

Effects of Autumn and Spring Heat Waves on Seed Germination of High Mountain Plants.

Alpine plants are considered to be particularly vulnerable to climate change and related extreme episodes, such as heat waves. Despite growing interest in the impact of heat waves on alpine plants, knowledge about their effects on regeneration is still fragmentary. Recruitment from seeds will be crucial for the successful migration and survival of these species and will play a key role in their future adaptation to climate change. In this study, we assessed the impacts of heat waves on the seed germination of 53 high mountain plants from the Northern Apennines (Italy). The seeds were exposed to laboratory simulations of three seasonal temperature treatments, derived from real data recorded at a meteorological station near the species growing site, which included two heat wave episodes that occurred both in spring 2003 and in autumn 2011. Moreover, to consider the effect of increasing drought conditions related to heat waves, seed germination was also investigated under four different water potentials. In the absence of heat waves, seed germination mainly occurred in spring, after seeds had experienced autumn and winter seasons. However, heat waves resulted in a significant increase of spring germination in c. 30% of the species and elicited autumn germination in 50%. When heat waves were coupled with drought, seed germination decreased in all species, but did not stop completely. Our results suggest that in the future, heat waves will affect the germination phenology of alpine plants, especially conditionally dormant and strictly cold-adapted chorotypes, by shifting the emergence time from spring to autumn and by increasing the proportion of emerged seedlings. The detrimental effects of heat waves on recruitment success is less likely to be due to the inhibition of seed germination per se, but rather due to seedling survival in seasons, and temperature and water conditions that they are not used to experiencing. Changes in the proportion and timing of emergence suggest that there may be major implications for future plant population size and structure.

Understanding the molecular pathways associated with seed vigor.

Farmers and growers are constantly looking for high quality seeds able to ensure uniform field establishment and increased production. Seed priming is used to induce pre-germinative metabolism and then enhance germination efficiency and crop yields. It has been hypothesized that priming treatments might also improve stress tolerance in germinating seeds, leaving a sort of 'stress memory'. However, the molecular bases of priming still need to be clarified and the identification of molecular indicators of seed vigor is nowadays a relevant goal for the basic and applied research in seed biology. It is generally acknowledged that enhanced seed vigor and successful priming depend on DNA repair mechanisms, activated during imbibition. The complexity of the networks of DNA damage control/repair functions has been only partially elucidated in plants and the specific literature that address seeds remains scanty. The DNA repair pathways hereby described (Nucleotide and Base Excision Repair, Non-Homologous End Joining, Homologous Recombination) play specific roles, all of them being critical to ensure genome stability. This review also focuses on some novel regulatory mechanisms of DNA repair (chromatin remodeling and small RNAs) while the possible use of telomere sequences as markers of aging in seed banks is discussed. The significant contribution provided by Electron Paramagnetic Resonance in elucidating the kinetics of seed aging, in terms of free radical profiles and membrane integrity is reported.

Climate warming could shift the timing of seed germination in alpine plants.

BACKGROUND AND AIMS: Despite the considerable number of studies on the impacts of climate change on alpine plants, there have been few attempts to investigate its effect on regeneration. Recruitment from seeds is a key event in the life-history of plants, affecting their spread and evolution and seasonal changes in climate will inevitably affect recruitment success. Here, an investigation was made of how climate change will affect the timing and the level of germination in eight alpine species of the glacier foreland. METHODS: Using a novel approach which considered the altitudinal variation of temperature as a surrogate for future climate scenarios, seeds were exposed to 12 different cycles of simulated seasonal temperatures in the laboratory, derived from measurements at the soil surface at the study site. KEY RESULTS: Under present climatic conditions, germination occurred in spring, in all but one species, after seeds had experienced autumn and winter seasons. However, autumn warming resulted in a significant increase in germination in all but two species. In contrast, seed germination was less sensitive to changes in spring and/or winter temperatures, which affected only three species. CONCLUSIONS: Climate warming will lead to a shift from spring to autumn emergence but the extent of this change across species will be driven by seed dormancy status. Ungerminated seeds at the end of autumn will be exposed to shorter winter seasons and lower spring temperatures in a future, warmer climate, but these changes will only have a minor impact on germination. The extent to which climate change will be detrimental to regeneration from seed is less likely to be due to a significant negative effect on germination per se, but rather to seedling emergence in seasons that the species are not adapted to experience. Emergence in autumn could have major implications for species currently adapted to emerge in spring.

Seeds of alpine plants are short lived: implications for long-term conservation.

BACKGROUND AND AIMS: Alpine plants are considered one of the groups of species most sensitive to the direct and indirect threats to ecosystems caused by land use and climate change. Collecting and banking seeds of plant species is recognized as an effective tool for providing propagating material to re-establish wild plant populations and for habitat repair. However, seeds from cold wet environments have been shown to be relatively short lived in storage, and therefore successful long-term seed conservation for alpine plants may be difficult. Here, the life spans of 69 seed lots representing 63 related species from alpine and lowland locations from northern Italy are compared. METHODS: Seeds were placed into experimental storage at 45 °C and 60 % relative humidity (RH) and regularly sampled for germination. The time taken in storage for viability to fall to 50 % (p(50)) was determined using probit analysis and used as a measure of relative seed longevity between seed lots. KEY RESULTS: Across species, p(50) at 45 °C and 60 % RH varied from 4·7 to 95·5 d. Seed lots from alpine populations/species had significantly lower p(50) values compared with those from lowland populations/species; the lowland seed lots showed a slower rate of loss of germinability, higher initial seed viability, or both. Seeds were progressively longer lived with increased temperature and decreased rainfall at the collecting site. CONCLUSIONS: Seeds of alpine plants are short lived in storage compared with those from lowland populations/related taxa. The lower resistance to ageing in seeds of alpine plants may arise from low selection pressure for seed resistance to ageing and/or damage incurred during seed development due to the cool wet conditions of the alpine climate. Long-term seed conservation of several alpine species using conventional seed banking methods will be problematic.