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The evolving threat of rapid Ohia death (ROD) to Hawaii’s native ecosystems and rare plant species

June 24, 2019

Hawai‘i’s most widespread native tree, ‘ōhi‘a lehua (Metrosideros polymorpha), has been dying across large areas of Hawai‘i Island mainly due to two fungal pathogens (Ceratocystis lukuohia and Ceratocystis huliohia) that cause a disease collectively known as Rapid ‘Ōhi‘a Death (ROD). Here we examine patterns of positive detections of C. lukuohia as it has been linked to the larger mortality events across Hawai‘i Island. Our analysis compares the environmental range of C. lukuohia and its spread over time through the known climatic range and distribution of ‘ōhi‘a. Analyses show this fungal pathogen generally encompassed the core, but not the extremes of the climatic range of ‘ōhi‘a. We further modeled the potential distribution of C. lukuohiaacross the Hawaiian Archipelago to estimate the risk of ROD to other islands. Given the potential for C. lukuohia to alter the structure of ‘ōhi‘a dominated forests, we used our projected potential distribution of C. lukuohia to assess the risk of ROD to threatened and endangered plant species across Hawai‘i. Many native plants are likely vulnerable to these types of large ‘ōhi‘a mortality events: of 234 endangered native plant species considered, 147 (62.8%) have more than half of their range within current and expanding C. lukuohia suitable areas. We also found evidence that protecting habitat by fencing out introduced feral ungulates reduces the prevalence of the disease likely by reducing physical damage caused by these animals to ‘ōhi‘a trees, a precondition for Ceratocystis infection. Given the ongoing spread of C. lukuohia, we developed a dynamic web portal to host our results online, where models and analyses are updated with new lab-confirmed detections to provide managers with a useful tool to help monitor and assess the risk of C. lukuohia as it continues to spread.

Publication Year 2019
Title The evolving threat of rapid Ohia death (ROD) to Hawaii’s native ecosystems and rare plant species
DOI 10.1016/j.foreco.2019.06.025
Authors Lucas B. Fortini, Lauren R. Kaiser, Lisa Keith, Jonathan Price, R. Flint Hughes, James D. Jacobi, J. B. Friday
Publication Type Article
Publication Subtype Journal Article
Series Title Forest Ecology and Management
Index ID 70203981
Record Source USGS Publications Warehouse
USGS Organization Pacific Island Ecosystems Research Center