Reintroduction of Delissea kauaiensis, a critically endangered lobeliad, on Kauai, Hawaii, USA

Summary

Delissea kauaiensis, a small tree in the bellflower family endemic to Kauai, has been reduced by feral goats, deer and pigs to just seven known mature wild plants scattered across four valleys too far apart for natural cross-pollination. Hawaii's Plant Extinction Prevention Program has spent nine years monitoring and collecting from these founders, while the state built five fenced, animal-free exclosures within the Kuia Natural Area Reserve between 2009 and 2013 to hold new populations representing the species' full remaining genetic diversity. The first planting, in 2010, put 124 plants from a single founder into one exclosure; as propagules from other founders became available they were added there and to two further sites, bringing the total past 500 plants representing seven of the eight known founders across three exclosures, with two more exclosures still awaiting animal removal or planting stock. The first site saw flowering and fruiting within a year and seedling recruitment within two, though those recruits are not yet mature; the second site had higher mortality and no recruitment yet, which the team traces to competition from invasive strawberry guava that was still being cleared when planting began; the third site, started in 2016, is too new to assess. The project is rated partially successful, having secured every wild individual in cultivation but not yet demonstrated a fully self-sustaining new population.