The global conservation status of plants growing on cliffs and rocky outcrops

Ecosystems that occur on cliffs and rocky outcrops are home to many plants that are specially adapted to harsh environmental conditions. These habitats are seeing increased pressure from development, recreational use, and invasive species, calling for a thorough evaluation of the endangerment of the taxa inhabiting them. However, the conservation status of these taxa is not well understood preventing effective conservation prioritization and action. In this study, we examine the conservation status of vascular plant taxa associated with these ecosystems, using the International Union for Conservation of Nature (IUCN) Red List of Threatened Species assessments, and compare these to their taxonomic status (families and genera) and range (realm, country, occupancy). We have assembled data highlighting regions where cliff and rocky outcrop taxa most frequently occur (Madagascar, Brazil, Spain) and found that plants growing in these habitats may be more endangered than expected given global plant endangerment, however, risk patterns do vary. Certain groups find refuge in cliffs or rocky outcrops environments (Euphorbiaceae, 18% less endangered), while others may be facing increased risk (Cactaceae, 19% more endangered). We have also found that taxa occurring in habitats with low mean elevation or narrow elevational ranges are more endangered. To assist future research, we have developed a dashboard summarizing available data that also allows for interactive analyses based on user-defined goals. We see the need for additional research on cliff and rocky outcrop plants to enhance the Red List assessment process and support overall plant conservation efforts.</p

Variability in seed salinity tolerance in an island coastal community

BACKGROUND AND AIMS: Island communities, with their long coastlines and increased vulnerability to sea level rise, offer compelling opportunities to investigate salinity tolerance of coastal plants. Seeds are generally more vulnerable than other plant stages to increased stressors. The aim of this study is 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.</p

Supporting long-term sustainability of ex situ collections using a pedigree-based population management approach

PREMISE: Living collections maintained for generations are at risk of diversity loss, inbreeding, and adaptation to cultivation. To address these concerns, the zoo community uses pedigrees to track individuals and implement crosses that maximize founder contributions and minimize inbreeding. Using a pedigree management approach, we demonstrate how conducting strategic crosses can minimize genetic issues that have arisen under current practices. METHODS: We performed crosses between collections and compared progeny fitness, including plant performance and reproductive health. We genotyped the progeny and parental accessions to measure changes in diversity and relatedness within and between accessions. RESULTS: The mean relatedness values among individuals within each accession suggest they are full siblings, demonstrating that there was high inbreeding and low diversity within accessions, although less so among accessions. Progeny from the wider crosses had increased genetic diversity and were larger and more fertile, while self‐pollinated accessions were smaller and less fertile. DISCUSSION: Institutions that hold exceptional species should consider how diversity is maintained within their collections. Implementing a pedigree‐based approach to managing plant reproduction ex situ will slow the inevitable loss of genetic diversity and, in turn, result in healthier collections

Variation in Germination Traits Inform Conservation Planning of Hawaiʻi's Foundational ʻŌhiʻa Trees

Climate can play a critical role in seed development and germination. Linking seed germination information with environmental variables and provenance may be important in understanding plant community structure and response to climate change, which can help guide conservation planning. Native Hawaiian Metrosideros (Myrtaceae; ʻŌhiʻa) is a hyperdiverse species complex that dominates Hawaiʻi's wet and mesic forests and serves as the most bioculturally important native plant in Hawaiʻi. In response to Rapid ʻŌhiʻa Death, a major threat to native forests caused by introduced fungal pathogens, seed collections of ʻŌhiʻa across the state have increased. We used initial seed germination data from recent collections stored in the National Tropical Botanical Garden’s Seed Bank to explore if seed germinability is correlated with seed zones and environmental variables. Linear models of the proportion of seed germinated, seed zones, and environmental data revealed that only seed zones were significantly correlated with the proportion germinated. Seed germination was lower for the “Nā Pali Valleys” than the “Windward Ranges.” Generalized provisional seed zones are a helpful tool for conservation collecting and restoration planning. Germination data routinely collected for seed bank collections provide an easily accessible source of preliminary information for these purposes.</p

Flora / Pollination biology reveals challenges to restoring populations of Brighamia insignis (Campanulaceae), a critically endangered plant species from Hawai‘i

Understanding the reproductive biology of rare plant species is fundamental to managing their restoration. Brighamia insignis is a critically endangered Hawaiian lobeliad endemic to the islands of Kauai and Niihau. The flowers appear to be adapted for moth pollination although its putative pollinator is believed to be extinct or very rare. To confirm the pollination syndrome, document the breeding system, and identify potential pollinators of B. insignis: 1) a suite of floral characters were examined, 2) pollination treatments were performed, and 3) diurnal and nocturnal floral visitor observations were conducted at an ex situ site on Kaua‘i. Brighamia insignis flowers contain sucrose-rich nectar and emit a strong floral scent containing benzyl alcohol, linalool, and methyl salicylate. Pollination treatments revealed that the species is primarily outcrossing with several of the study plants also capable of low levels of selfing. However, most of the plants had low pollen production and viability. No moths and only occasional non-native insect species visited the flowers of B. insignis. None of these insect visitors appeared to be serving as effective pollinators. In spite of this lack of flower visitation by moths, analysis of nectar and floral scent support a moth pollination syndrome in B. insignis. The potential loss of pollinators suggests that restoring populations of B. insignis may not be feasible; human assisted cross-pollination would be necessary for fruit and seed to set, as only 1% of the control and self treatment flowers formed fruit. Therefore, this species appears dependent upon intense human management to prevent its extinction.(VLID)439382