First phase of the re-introduction of Silene hifacensis (Caryophyllaceae) in Cap de Sant Antoni, Valencian Community, Spain

Summary

Silene hifacensis, a Spanish endemic cliff-dwelling shrub protected under the Bern Convention, had vanished from its Iberian type locality at Cap de Sant Antoni, Valencian Community, after previous reintroduction attempts there and at a nearby site repeatedly failed since the plant's 1987 rediscovery, including a 1999 sowing of 3,200 seeds that left only two surviving adults twelve years later. Since 2008, Spain's regional Biodiversity Service cultivated 240 new mother plants in four separate nurseries from each native Iberian sub-population to preserve genetic separation, while a small donor population of just four accessible plants on an offshore islet produced over 100,000 seeds by 2011. Learning from past failures on horizontal or low-cliff sites, the team targeted the unoccupied 130-meter cliff crown of Cap de Sant Antoni, a site less accessible to rabbits, rats and casual damage, where experienced rock-climbing park rangers sowed 30 microsites along 250 meters of cliff face between October 2009 and February 2010, followed by seedling reposition at 10 failed microsites and monthly monitoring with supplemental watering during droughts. By summer 2011, over 200 seedlings had been planted across 34 monitoring visits, and three individuals (10% of the initial pool) flowered and set seed, with only sporadic snail predation observed. Major difficulties included the inaccessibility of donor seed sources, the physical risk of high-cliff plantation work, and unreliable microsite quality. The project rates itself Partially Successful, framing this as only a first phase toward true reintroduction, with success provable only after long-term monitoring of natural regeneration.