Advances in the recovery of Galvezia leucantha subsp. leucantha (Plantaginaceae): restoring a critically endangered species on northern Isabela Island, Galápagos

Galvezia leucantha subsp. leucantha is a critically endangered endemic plant of the Galápagos Islands that has suffered drastic population declines due to introduced herbivores and habitat degradation. By 2007, only six individuals remained on northern Isabela Island. In response, the Charles Darwin Foundation, through its Galápagos Verde 2050 Program, implemented a long-term conservation strategy aimed at restoring viable wild populations. This study aimed to support the recovery of this subspecies by combining ex situ propagation with in situ restoration and reintroduction. Morphological traits were documented through high-resolution dissection plates. Seed viability and germination were tested under different pretreatment and substrate conditions. Seedling growth, flowering phenology, and transplant survival were monitored to identify key criteria for restoration success. G. leucantha subsp. leucantha exhibits distinct floral traits, and this study provides the first standarized and detailed visual record documenting its floral morphology. Seed viability reached a maximum of 52.9% when water-treated and recently collected seeds were used. Sodium hypochlorite (3%) significantly improved germination. However, no statistically significant effect on seed viability was detected, and the available data remain insufficient to determine its impact conclusively. Seedlings showed biphasic growth, reaching heights ≥ 60 cm—identified as the minimum threshold for successful outplanting. From 2017 to 2024, 94 nursery-grown plants were outplanted to Playa Tortuga Negra and Caleta Tagus and continuously monitored for subsequent survival. Flowering (October–January) and natural seedling recruitment were recorded at both sites. This study shows how integrating ex situ propagation, monitoring, and adaptive reintroduction can support the recovery of narrowly distributed island endemics. This approach increased the wild adult population to 20 individuals and successfully re-established a second population at a site where the species had been previously extirpated.