Sonoran Desert ex situ conservation gap analysis: charting the path towards conservation

Plant biodiversity is under threat. With two out of five plants at risk of extinction, preserving taxa through ex situ conservation approaches must be considered a priority. The Sonoran Desert (SD), a highly biodiverse ecoregion shared between Mexico and the United States is home to over 4000 native plant taxa. A method to determine conservation priorities was developed in collaboration with institutions from both countries. Herbaria records and data from nine seed banks were analysed to identify gaps in previous conservation efforts. The SD native taxa were prioritised based on a Priority Score (PS) and their potential distribution was modelled to identify priority regions. 4029 native taxa were reported. 1441 have accessions preserved in seed banks, but only 412 have been collected inside the SD. The PS considers some potentially endemic (126) and threatened taxa (112) as the most urgent to preserve. It also includes information about the storage behaviour (3236 orthodox), useful plants (1406), and taxa without populations in protected areas (230) to categorise the species. Although most of the SD flora is not represented in seed banks, at least 80% is predicted to produce desiccation-tolerant seeds and thus can be cost-effectively stored. Spatial analysis shows that the central region of the Baja California Peninsula stands out for its species richness and endemism. Our study presents the first ex situ conservation gap analysis of the SD flora and provides a replicable methodology for identifying priority species and potential areas for ex situ collection.