The intersection of basic research and conservation: a 30-year study of the Critically Endangered Schiedea adamantis (Caryophyllaceae) on Le ¯‘ahi (Diamond Head Crater), Hawai‘i A NN K. S AKAI ,S TEPHEN G. W ELLER ,W EIGANG Y ANG ,S USAN C HING H ARBIN T ALIA P ORTNER ,G REG M ANSKER and M ARIE B RUEGMANN Abstract We report on how a long-term study of the reproductive biology of the Critically Endangered Schiedea adamantis (Caryophyllaceae), one of Hawai‘i’s rarest plant species, was leveraged for conservation purposes. Our major goals were to provide seeds with the greatest genetic vari- ation possible for reintroduction and to ensure that both female and hermaphroditic plants of this wind-pollinated species were reintroduced in a manner that maximized both outcrossing and seed production. Schiedea adamantis was one of the first Hawaiian plant species listed under the Endangered Species Act (USA). The species has been stud- ied intensively to test hypotheses addressing the evolution of breeding systems. Information on outcrossing levels and the extent of inbreeding depression was integrated into ongoing reintroduction efforts. Population size peaked in , when  flowering individuals were found on Lē‘ahi (Diamond Head Crater). By  only  flowering individuals were present, with drought and invasive species being possible causes of this decline. Reintroduction attempts in  using genetically diverse seeds were unsuccessful because of drought and a lack of sufficient supplemental irrigation. Additional reintroduction attempts in  and  were more successful because of increased supplemental irriga- tion. Plants used in reintroductions represent genotypes long since absent in the natural population, and may con- tain the genetic variability essential for evolutionary re- sponses to climate change and the spread of invasive species. The destruction of many plants reintroduced in  and  by a fire in March  highlights the need for additional restoration areas at Lē‘ahi and elsewhere, and storage of seeds for future use. Keywords Conservation, Diamond Head Crater, gynodioecy, Lē‘ahi, reintroduction, reproductive systems, Schiedea adamantis, quantitative genetics Introduction B asic research questions on the evolution of reproductive systems and the conservation of threatened species are often addressed independently by practitioners in these two areas. However, at a fundamental level both disciplines are united in the need to understand factors affecting popula- tion size and genetic variation. We report here a long-term study of the reproductive biology of one of Hawai‘i’s rarest plant species, and how the results were leveraged for conser- vation purposes. Our first major conservation goal for Schiedea adamantis St. John (Caryophyllaceae) was to pro- vide seeds for conservation that represented the maximum level of genetic variation possible, using material collected prior to a severe decline in the size of the sole population of this species. An outplanting strategy was established to avoid inbreeding among closely related individuals. Our se- cond major goal was to use our knowledge of the pollination and reproductive systems of S. adamantis to ensure that all plants used in restoration would have pollen sources close enough to ensure seed production. Schiedea adamantis is among the rarest species of Schiedea, a lineage of  species descended from a common ancestor and endemic to the Hawaiian Islands (Wagner et al., ). The genus Schiedea, because of its diversity of breeding systems, has served as a model system for under- standing the evolution of separate sexes (e.g. Weller et al., ; Sakai et al., ; Campbell et al., ). Schiedea ada- mantis has played a key role in testing hypotheses for the evolution of separate sexes because it is gynodioecious (fe- male and hermaphroditic plants in a population), a breeding system intermediate between hermaphroditism and full di- oecy (females and males in a population; Sakai et al., ). In gynodioecious species, females are necessarily out- crossed, whereas hermaphrodites may be outcrossing or po- tentially highly self-fertilizing. Information on reproductive systems is important for planning conservation efforts, to avoid the potential for deleterious effects caused by ANN K. SAKAI,STEPHEN G. WELLER (Corresponding author) and WEIGANG YANG Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697, USA. E-mail sgweller@uci.edu SUSAN CHING HARBIN and TALIA PORTNER O‘ahu Plant Extinction Prevention Program, Pearl City, Hawai‘i, USA GREG MANSKER Division of Forestry and Wildlife, Honolulu, Hawai‘i, USA MARIE BRUEGMANN United States Fish and Wildlife Service (retired), Dowagiac, Michigan, USA Received  June . Revision requested  August . Accepted  September . First published online  February . Oryx, 2018, 52(3), 479–488 © 2017 Fauna & Flora International doi:10.1017/S0030605316001162 https://doi.org/10.1017/S0030605316001162 Downloaded from https://www.cambridge.org/core. IP address: 54.226.142.93, on 21 Jan 2022 at 16:44:04, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms.