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 variation 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 studied 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 1994, when 267 flowering individuals were found on Lē‘ahi (Diamond Head Crater). By 2016 only 17 flowering individuals were present, with drought and invasive species being possible causes of this decline. Reintroduction attempts in 1998 using genetically diverse seeds were unsuccessful because of drought and a lack of sufficient supplemental irrigation. Additional reintroduction attempts in 2012 and 2014 were more successful because of increased supplemental irrigation. Plants used in reintroductions represent genotypes long since absent in the natural population, and may contain the genetic variability essential for evolutionary responses to climate change and the spread of invasive species. The destruction of many plants reintroduced in 2015 and 2016 by a fire in March 2016 highlights the need for additional restoration areas at Lē‘ahi and elsewhere, and storage of seeds for future use.

Gynodioecy is a dimorphic breeding system in which hermaphrodites coexist with male steriles in natural populations. Theoretical models predict that without any compensation in female fitness, male steriles will quickly disappear from a population. The amount of compensation required depends upon the mode of inheritance. In this study we investigated whether performance, during early vegetative growth, could play a role in the maintenance of male steriles in populations of gynodioecious self-incompatible Plantago lanceolata. This was accomplished by comparing the growth of the predominant male-sterile type from a natural population with two hermaphroditic types. One of the hermaphroditic types differed from the male sterile only in nuclear genome, having the same type of cytoplasm. The other type was nuclearly nearly isogenic, but had a different cytoplasm. Plants were grown under controlled conditions, either in near-optimal hydroponic solutions, or in a range of N- supplies on sand. A detailed growth analysis was carried out, and the relative growth rate (RGR) of each type was analysed into its underlying components, the net assimilation rate, the leaf mass ratio and the specific leaf area. No difference between the sex types in relative growth rate was found and, in the components underlying the RGR, only a few small differences were detected. In none of the growth parameters examined did the male steriles differ from either hermaphroditic type. Differences in plant growth related to N-supply, differences in growth on hydroponics compared with sand culture, as well as the maintenance of male sterility in populations of P. lanceolata are discussed.