Variability in seed salinity tolerance in an island coastal community.

BACKGROUND AND AIMS: Islands, with their long coastlines and increased vulnerability to sea level rise, offer compelling opportunities to investigate the salinity tolerance of coastal plants. Seeds are generally more vulnerable than other plant stages to increased stressors. The aim of this study was to characterize salinity tolerance during germination across a diverse pool of 21 species from 14 plant families found in coastal communities throughout the Hawaiian Islands in order to increase our general understanding of coastal plant ecology for conservation and restoration. METHODS: Seeds of each species were exposed to unfiltered/untreated seawater (35 ppt total salinity) and two salinity treatments (10 and 20 ppt) in which the seawater was diluted with distilled water, and germination percent and timing were compared to seeds in a distilled water control. Non-germinated seeds were then tested for recovery germination. We quantified and compared germination percent, time and recovery among species and across salinity levels and tested for heterogeneity related to seed size, dormancy class, habit and threatened status. KEY RESULTS: Although salinity tolerance varied considerably among species, salinity exposure generally reduced and delayed germination. The greatest effects were detected at higher salinity levels. Recovery germination overall was higher for seeds that had been exposed to higher salinity. None of the factors we explored emerged as predictors of salinity tolerance except seed mass, which tended to enhance germination at higher salinity. CONCLUSIONS: Species responses to salinity exposure indicate high vulnerability of coastal systems to increased salinity stress, and variability among species could lead to shifts in community assembly and composition under sea level rise. These results can help guide coastal ecosystem conservation and restoration management decisions in the face of climate change.

Seed dormancy and germination of the endangered exceptional Hawaiian lobelioid Brighamia rockii.

Premise: The Campanulaceae (Lobelioideae) is the Hawaiian plant family with the most endangered and extinct species. Although seeds of Hawaiian lobelioids are desiccation tolerant, the species are exceptional (i.e., they present challenges at various stages of the conventional ex situ conservation chain) due to their generally poor seed survival at the conventional seed-banking temperature (-18°C). Both morphological dormancy (MD) and morphophysiological dormancy (MPD) have been identified in the seeds of other Hawaiian lobelioids; however, the class of dormancy and germination requirements of the Critically Endangered genus Brighamia have not yet been determined. Methods: We measured the embryonic growth in 12-week-old seeds of B. rockii and tested their germination at three temperature regimes (15/5°C, 20/10°C, and 25/15°C) in light and at 25/15°C in darkness. Results: The embryos grew prior to radicle emergence, and the seeds germinated rapidly to high percentages in all tested conditions. Discussion: Whether fresh B. rockii seeds have MD or MPD still needs to be determined; nevertheless, 12-week-old seeds germinated well in light and darkness, and thus the seeds can be used for conservation purposes. Germination in the dark suggests that the species may not form a long-lived soil seed bank in its native habitat.

Extinction risk of the endemic vascular flora of Kauai, Hawaii, based on IUCN assessments.

The International Union for Conservation of Nature's Red List of Threatened Species (IUCN Red List) is the world's most comprehensive information source on the global conservation status of species. Governmental agencies and conservation organizations increasingly rely on IUCN Red List assessments to develop conservation policies and priorities. Funding agencies use the assessments as evaluation criteria, and researchers use meta-analysis of red-list data to address fundamental and applied conservation science questions. However, the circa 143,000 IUCN assessments represent a fraction of the world's biodiversity and are biased in regional and organismal coverage. These biases may affect conservation priorities, funding, and uses of these data to understand global patterns. Isolated oceanic islands are characterized by high endemicity, but the unique biodiversity of many islands is experiencing high extinction rates. The archipelago of Hawaii has one of the highest levels of endemism of any floristic region; 90% of its 1367 native vascular plant taxa are classified as endemic. We used the IUCN's assessment of the complete single-island endemic (SIE) vascular plant flora of Kauai, Hawaii, to assess the proportion and drivers of decline of threatened plants in an oceanic island setting. We compared the IUCN assessments with federal, state, and other local assessments of Kauai species or taxa of conservation concern. Finally, we conducted a preliminary assessment for all 1044 native vascular plants of Hawaii based on IUCN criterion B by estimating area of occupancy, extent of occurrence, and number of locations to determine whether the pattern found for the SIE vascular flora of Kauai is comparable to the native vascular flora of the Hawaiian Islands. We compared our results with patterns observed for assessments of other floras. According to IUCN, 256 SIE vascular plant taxa are threatened with extinction and 5% are already extinct. This is the highest extinction risk reported for any flora to date. The preliminary assessment of the native vascular flora of Hawaii showed that 72% (753 taxa) is threatened. The flora of Hawaii may be one of the world's most threatened; thus, increased and novel conservation measures in the state and on other remote oceanic islands are urgently needed.

La Lista Roja de la Unión Internacional para la Conservación de la Naturaleza (Lista Roja UICN) es la fuente más completa a nivel mundial de información sobre el estado de conservación de las especies. Las agencias gubernamentales y las organizaciones para la conservación dependen cada vez más de las valoraciones en esta lista para desarrollar sus políticas y prioridades de conservación; también los organismos de financiamiento usan las valoraciones como criterios de evaluación y los investigadores aplican metaanálisis a los datos de la lista para abordar preguntas fundamentales y aplicadas a las ciencias de la conservación. Sin embargo, las casi 143,000 valoraciones de la UICN representan sólo una fracción de la biodiversidad mundial y están sesgadas en cuanto a la cobertura regional y de organismos. Estos sesgos pueden afectar a las prioridades de conservación, al financiamiento y al uso de estos datos para entender los patrones globales. Las islas oceánicas aisladas se caracterizan por un alto endemismo, aunque la biodiversidad única de muchas de estas islas está experimentando un índice elevado de extinciones. El archipiélago de Hawái tiene uno de los niveles más altos de endemismo de cualquier región florística con el 90% de los 1,367 taxones nativos de flora vascular clasificado como endémico. Usamos las valoraciones de la UICN para todas las plantas vasculares endémicas de una sola isla (ESI) en Kauai, Hawái, para evaluar la proporción y los impulsores de la declinación de plantas amenazadas en el entorno de una isla oceánica. Comparamos las valoraciones de la UICN con las federales, estatales y otras valoraciones locales de las especies o taxones de Kauai que son de importancia para la conservación. Por último, realizamos una valoración preliminar para las 1,044 especies de plantas vasculares nativas de Hawái con base en el criterio B de la UICN mediante la estimación del área de ocupación, la extensión de la ocurrencia y el número de localidades para determinar si el patrón hallado para la flora vascular ESI de Kauai es comparable con la flora vascular nativa de las islas hawaianas. Comparamos nuestros resultados con los patrones observados en las valoraciones de otras floras. De acuerdo con la UICN, el 95% de los taxones de plantas vasculares ESI de Kauai están amenazadas y el 5% ya se encuentra extinto. A la fecha, este es el riesgo de extinción más alto reportado para cualquier flora. La valoración preliminar de la flora vascular nativa de Hawái mostró que el 72% (753 taxones) se encuentra amenazado. La flora de Hawái puede ser una de las más amenazadas a nivel mundial; por lo tanto, se necesitan urgentemente medidas novedosas e incrementadas en el estado y en otras islas oceánicas remotas.

Conservation seed physiology of the ciénega endemic, Eryngium sparganophyllum (Apiaceae).

Knowledge of seed dormancy and optimal propagation techniques is crucial for successful ex situ restoration and reintroduction projects, and determining the seed storage behaviour of a species is critical for the long-term conservation of seeds, further supporting future ex situ efforts. Eryngium sparganophyllum (Apiaceae) is a globally critically endangered plant species endemic to ciénega wetlands of southwest North America. To support in situ and ex situ conservation efforts of E. sparganophyllum, we asked (i) how does the embryo: seed (E:S) ratio change over time once imbibed, (ii) how does germination respond with varying periods of exposure to cold (5°C) and warm (25°C) stratification, and concentrations of gibberellic acid (GA3). By answering these questions, (iii) can dormancy class be inferred, and (iv) what storage behaviour category is exhibited? To answer these questions, we collected seeds in Southern Arizona from one of the few remaining wild populations. We measured embryo growth and tested the effects of cold (0-18 weeks) and warm (0 and 4 weeks) stratification, and 0-1000 ppm gibberellic acid on germination. We also tested the effects of cold (-80°C) dry (~20% equilibrium relative humidity) storage on germination. We found that (i) embryos grow inside seeds prior to germination; (ii) compared to control, cold stratification for at least 6 weeks increased germination and warm stratification had no effect; (iii) 1000-ppm GA3 had the highest germination success; (iv) therefore this species exhibits morphophysiological dormancy; and (v) seeds are orthodox and can therefore be conserved using conventional storage methods. This information will aid managers in the propagation of E. sparganophyllum that is crucial for in situ reintroduction and restoration projects, and seed banking represents a critical ex situ conservation strategy for the preservation of this species.

Seed freeze sensitivity and ex situ longevity of 295 species in the native Hawaiian flora.

PREMISE: Ex situ seed banking is critical for plant conservation globally, especially for threatened floras in tropical ecosystems like Hawai'i. Seed bank managers must maximize longevity, and species managers must plan restoration before seeds lose viability. Previous observations suggested some native Hawaiian seeds lost viability in frozen storage (-18°C). We investigated seed storage behavior in the Hawaiian flora to optimize storage conditions and recommend re-collection intervals (RCI) to maximize viability of stored seeds. METHODS: Using 20+ years of real-time seed storage viability data, we tested freeze sensitivity for 197 species and calculated RCIs for 295 species. Using paired tests of accessions stored >2 yr at 5°C and -18°C, we developed an index of relative performance to determine freeze sensitivity. We calculated RCIs at 70% of highest germination (P70). RESULTS: We identified four families (Campanulaceae, Cyperaceae, Rubiaceae, and Urticaceae) and four genera with seed freeze sensitivity and six additional genera with likely freeze sensitivity. Storage longevity was variable, but 195 species had viability >70% at the most recent tests (1 to 20+ yr), 123 species had RCIs >10 yr, and 45 species had RCIs <5 yr. CONCLUSIONS: Freeze sensitive storage behavior is more widely observed in Hawai'i than any other regional flora, perhaps due to insufficient testing elsewhere. We present a new protocol to test seed freeze sensitivity, which is often not evident until 2-5 years of storage. Re-collection intervals will guide restoration practices in Hawai'i, and results inform seed conservation efforts globally, especially tropical and subtropical regions.

Picking from the Past in Preparation for a Pest: Seed Banks Outperform Herbaria as Sources of Preserved 'Ohi'a Seed.

Seed banks serve the purpose of maintaining germplasm for ex situ species preservation. Herbarium vouchers may be a viable source of unique and/or additional seeds for restoration as they can sometimes be from larger and more representative populations compared with seed banks. Rapid 'ohi'a death (ROD) has emerged as a serious threat against Hawaii's most iconic and foundational forest tree (Metrosideros spp.), and seed banking has been identified as an important strategy in preserving the genetic diversity of 'ohi'a. With respect to 'ohi'a we ask the following: (1) what is the long-term viability of 'ohi'a seeds stored in herbarium conditions, (2) how do herbarium curation practices affect seed viability, and (3) how long do seeds survive using conventional storage methods? We placed fresh 'ohi'a seeds in a herbarium dryer (57°C/5% relative humidity) for 5 days, freezer (-18°C/95% RH) for 2 weeks, and dryer then freezer, and compared against fresh control seeds. Seeds were harvested from a chronosequence of herbarium specimens, withdrawn from conventional storage conditions up to 3.75 and 6.5 years before experiments began, and germination assessed. There was no difference in the proportion germinated among treatments and control testing for herbarium entry (p = 0.56). Although no seeds from herbarium specimens germinated, freshly collected dried and frozen seeds germinated at a level equivalent to the control (p = 0.76). For seeds stored using conventional storage methods at 3.75 and 6.5 years, germination was equivalent to freshly harvested seeds. This suggests that seeds can survive the extreme climate conditions necessary to enter herbaria, but lose viability after storage at ambient conditions in 4 years or less. Although 'ohi'a seeds may be plentiful in herbaria, we recommend using seeds deposited into seed banks using conventional storage methods for orthodox seeds for postdisturbance restoration, and to combat ROD.