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Premise of research. The explosive diversification of Hawaiian Bidens is considered one of the premier examples of plant adaptive radiation in the native Hawaiian flora. Botanical exploration, especially in remote areas, continues and sometimes results in the discovery of new species. Most of these new discoveries are narrowly distributed endemics, and some are evaluated to be threatened or endangered, sometimes critically so, as is the case for Bidens wailele. Methodology. Bidens wailele K.R. Wood & Knope (Asteraceae/Compositae) is (1) described and illustrated from Kauai, Hawaiian Islands; we also (2) provide a diagnostic key distinguishing characters that separate B. wailele from all other native Kauai Bidens , (3) present a summary of its distribution, ecology, and threats; and (4) provide a formal Red List assessment utilizing the International Union for Conservation of Nature (IUCN) criteria for endangerment. This discovery is part of ongoing floristic research and exploration conducted by the National Tropical Botanical Garden Science and Conservation Department. Pivotal results. This new species occurs in extremely wet conditions around the waterfalls of Waialeale and Wainiha, central Kauai. Morphologically, it is most similar to Bidens valida , a Kauai endemic species naturally occurring around windswept ridges and cliffs of southeastern Kauai (as on Haupu, Hulua, and Kahili Mountains). Conclusions. This rare new species is presently known from only 700–800 individuals and restricted to three remote locations; B. wailele has been evaluated under the IUCN Red List criteria and proposed as critically endangered. A fourth population on a wet cliff where the new species historically occurred (i.e., Kamanu, Kauai) was destroyed by a landslide after its discovery in 2008, most likely caused by torrential rains and demonstrating the species' vulnerability for extinction. [ABSTRACT FROM AUTHOR]

More than one third of the USA's federally listed endangered and threatened plants are endemic to Hawaii. Because of the accelerating rate of environmental pressures resulting from habitat degradation to loss, the Hawaiian Rare Plant Program (HRPP, Lyon Arboretum, Honolulu, Hawaii) utilizes in vitro culture and seed storage to rescue, recover, and restore Hawaii's most critically endangered native plant taxa. These in vitro methods complement existing ex situ and in situ efforts in the state. Wild-collected seeds tend to be hard to clean, and obtaining contamination-free seeds or embryos without damage or over sterilization is one of the most difficult obstacles in the successful establishment of in vitro cultures. Loss of rare and valuable propagation material occurs when seed samples succumb to contamination or mortality during the initial disinfestation stage. This study reviews pre-treatments and provides examples of three general disinfestation protocols successfully used in the HRPP to establish axenic ovule and embryo cultures of some endangered Hawaiian species. Three disinfestation protocols are described: bleach sterilization, gas sterilization, and ethanol dip and flame. Since 1998, the HRPP has been successful in establishing in vitro cultures of 135 endangered Hawaiian plant taxa representing 30 genera. [ABSTRACT FROM AUTHOR]

The Hawaiian flora, because of its great isolation, high levels of endemism, known lineages, and high rates of endangerment, offers unique opportunities to explore patterns of endangerment related to phylogeny, ecological and life history traits, and geographic patterns. Nine percent of the native flora of 1159 taxa are already extinct, and 52.5% are at risk (extinct, endangered, vulnerable, or rare). Risk is strongly associated with limited geographic distribution at several scales: endemic taxa (native only to the Hawaiian Islands) are at far greater risk than indigenous taxa (with both Hawaiian and extra-Hawaiian ranges); single-island endemics are more at risk than multi-island endemics; small islands have the highest proportion of endemic taxa at risk; and endemics with more limited habitat distributions (elevation, community type) are more at risk. Historic population density is a strong predictor of risk, and taxa with low historic population densities are at greatest risk with rapid anthropogenic changes. Among the major islands, Maui Nui has the highest percent of taxa that are extinct. Kaua'i has the lowest percent of extinct taxa and the highest proportion of single-island endemic taxa that are rare. Endemic taxa at risk are associated with distributions in shrublands, forests, bogs, and cliff habitats. Endemic taxa with distributions in low elevation dry habitats have the highest proportion of taxa at risk, but the greatest absolute numbers of taxa at risk have distributions in mesic lowland and montane forests, and in wet montane forests. The life history patterns associated with risk are complicated, and inclusion of the effects of evolutionary relationships (lineages) changes some of these patterns. Species level analyses without respect to lineage shows risk associated with monomorphic (hermaphroditic) breeding systems and bird pollination because of the large number of hermaphroditic, bird-pollinated species in the Campanulaceae. Analyses incorporating the effect of lineage greatly reduce the impact of large lineages and result in an association of risk with insect pollination, and no effect of breeding system. There is no association of lineage size and the percent of taxa at risk within the lineage; endemic taxa from lineages with large radiations are at no greater risk than endemic single-taxon lineages. The percentages of taxa at risk at the family level in the Hawaiian Islands and worldwide (excluding Hawaiian taxa) are positively correlated, although flowering plant families in the Hawaiian Islands have a much greater proportion of taxa at risk. Some of the approaches described here may be useful to predict geographical and biological patterns of endangerment in island and island-like ecosystems under increasing pressures of endangerment and extinction. [ABSTRACT FROM AUTHOR]