Seed viability Hawai‘i’s foundational-ʻōhi‘ trees linked environmental variables
Nina Rønsted, National Tropical Botanical Garden
Climate can play a critical role in plant physiological processes at all life stages, but investigations into climate effects often focus on only adult life stages. However, climate can influence seed development and germination, which can in turn strongly affect community dynamics. Native Hawaiian Metrosideros spp. (Myrtaceae; ʻōhi‘a,; 13 taxa) are the most dominant and ecologically important trees in mesic and wet rainforest ecosystems of Hawaiʻi. Aditionally, ʻōhi‘a are the most bioculturally important native plant in Hawai‘i. Recently, new fungal pathogens are causing rapid ʻōhi‘a death (ROD). As ʻōhi‘a are foundational species, ROD threatens the native forests that compose the majority of intact Hawaiian ecosystems. Making the most of Covid19 disruptions of our daily work, we used initial seed viability data from germination experiments routinely conducted by National Tropical Botanical Garden’s Seed Laboratory to explore if seed viability is correlated with collection locality and environmental variables. We included seed viability data of the most widespread and common taxon, M. polymorpha var. glaberrima, from 86 collection sites across Kauaʻi Island. Correlation of seed viability with environmental data from the Online Climate Atlas of Hawaiʻi was explored using linear models in R and suggest initial seed viability is correlated with mean temperature of coldest quarter and to a lesser extent with precipitation of warmest quarter reflecting the complex topology of Kauaʻi. As ROD threatens ʻōhi‘a across the islands, knowledge of these climatic effects on seed germination can be used as a proxy for understanding the health of populations across the distribution range and at its extremes. Linking seed viability information with environmental variables and locality can further help inform conservation priority planning as well as guide seed collection for safeguarding in seed banks.