First steps for the conservation translocation of the betic alder buckthorn in Eastern Spain

Summary

The betic alder buckthorn (Frangula alnus subsp. baetica), Vulnerable and split between a southern Spanish population and an isolated eastern population 500 km away along the Jucar river gorges, saw its eastern range mostly destroyed by a 1982 flood, leaving two subpopulations 15 km apart, totaling around 40 and 22 individuals, too far apart for cross-pollination and largely unable to produce fertile seed. Spain's Centre for Forestry Research and Experimentation began an ex-situ propagation program using cuttings from accessible Valencian individuals, refining an in-vitro protocol in 2008 and a hormoned-cutting method in 2010, building a clonal collection that reached 40 individuals from five lines by 2013 and, once compatible clones were cross-pollinated together, yielding the first substantial biodiverse seed harvests, over 1,400 seeds in 2011 and 2,500 fruits in 2012. Since 2009, 320 clonal plants have been planted at 19 riverbank sites along the Jucar and Cabriel rivers within the Hoces del Cabriel Nature Park, categorized as proximity reinforcements rather than true reinforcements of the inaccessible cliff-crevice native sites, with the first enrichment using ex-situ seed-grown plantlets carried out in winter 2012-2013. Monitoring found eight of the 19 planted sites achieving over 80% survival, with failures linked to salinity, fluctuating water levels and ibex foraging, and translocated plants first flowered in 2012, three years after planting. Difficulties included the wild population's low, mostly self-pollinated seed set and incomplete knowledge of optimal habitat following the flood. The project rates itself partially successful, noting definitive success will require translocating seed-derived plantlets, but early results are promising.