Floral biology and breeding system of the narrow endemic Dianthus morisianus Vals. (Caryophyllaceae)

• Dianthus morisianus is a narrow endemic plant of Sardinia.
• D. morisianus presents a long lifespan and a high degree of synchrony.
• D. morisianus is self-compatible and has a mixed mating system.
• D. morisianus shows a low level of inbreeding depression at the studied stages.

Dianthus morisianus Vals. (Caryophyllaceae) is a narrow endemic species of Sardinia, growing with only one natural population on the Portixeddu coastal dune system (southwest Sardinia). In this work we investigated the ex situ phenology and the breeding system through hand-pollination experiments to investigate whether this endemic plant presents inbreeding depression. D. morisianus had a floral lifespan of a week; the maximum flowering moment occurred in June and the cultivated plants presented high flowering synchrony. Among several traits measured, there were only differences in fruit set and first leaf appearance between geitonogamous and xenogamous treatments, and we detected differences in the number of seeds and first leaf appearance in accordance to the origin of the mother plant (mother effect). The plants cultivated ex situ present inbreeding depression only in germination time (T50), and the cumulative inbreeding depression was negligible. D. morisianus is self-compatible and presents facultative xenogamy as its breeding system. Our data suggest that inbreeding depression should not be a major issue in D. morisianus. The results of this study are of value for further conservation actions on natural population of this threatened endemic plant.