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.

New and resurrected Hawaiian species of pilo (Coprosma, Rubiaceae) from the island of Maui.

Two species of Coprosma (Rubiaceae) J.R.Forst. & G.Forst. are described from the island of Maui of the Hawaiian Archipelago. A newly described taxon, Coprosma cordicarpa J.Cantley, Sporck-Koehler, & M.Chau, sp. nov. is locally common in medium to high elevation dry forests and shrublands of leeward East Maui. The second taxon is resurrected from the synonymy of Coprosma foliosa A.Gray as Coprosma stephanocarpa Hillebr. and occurs in mesic to wet rainforests of both East and West Maui. Both taxa are segregated from Coprosma foliosa, with which they share similar morphological characters. A conspicuous and persistent calyx of the fruit and various floral characters most easily differentiate both taxa from other Hawaiian taxa. The newly described Coprosma cordicarpa is further distinguished from Coprosma stephanocarpa by a central constriction of the fruit with a depressed apex, which gives it a characteristic heart shape. Furthermore, the taxa are largely separated phenologically, ecologically, and geographically. Descriptions, conservation status, and specimens examined for the new species are included.

Ecological factors influencing growth of the endangered Hawaiian fern Marsilea villosa (Marsileaceae) and implications for conservation management.

PREMISE OF THE STUDY: Conserving endangered plants is a complex task, and practitioners must often use a "triage" approach, addressing only immediate needs. Ecologists can improve this process by conducting sound science upon which to base management. Marsilea villosa is an endangered, endemic Hawaiian fern with seven remaining populations in ephemerally flooding drylands. Among its uncommon traits are long-lived sporocarps, requiring flood and drought to complete its sexual life cycle, and extensive vegetative growth. METHODS: We conducted a 3-yr ecological field study, measuring percent cover of M. villosa and associated species, flooding depth, and canopy cover, to identify ecological factors with the greatest impact on M. villosa growth. KEY RESULTS: Maximum flooding depth and canopy cover had strong positive relationships with M. villosa growth, and all plots with >50% threshold of either variable reached 100% cover of M. villosa by the end of the study. Interaction effects explained nuances of these relationships, including synergy between the two variables. Percent cover of nonnative functional groups (graminoids and nongraminoids) each had negative relationships with M. villosa growth, but interactions showed that nongraminoid cover was driven by particular species, and that time since flooding had greater influence on M. villosa growth than graminoid cover. CONCLUSIONS: We recommend planting reintroduced populations in flood-prone areas with moderate shade, experimental outplanting of native plants with M. villosa, and management of graminoids as a functional group, while nongraminoid management should be species-specific. These practices will promote self-sustaining populations and reduce the need for labor-intensive management.