Genomic data define species delimitation in Liberica coffee with implications for crop development and conservation

Safeguarding the long-term future of the global coffee supply chain represents a major challenge, particularly in an era of accelerated climate change. Of particular concern are the millions of smallholder farmers across the tropical belt who rely on coffee as their major source of income. The world's coffee farmers, and thus the global coffee supply chain, rely on two species: Arabica (Coffea arabica) and robusta (Coffea canephora)¹. A third species, Coffea liberica, including Liberica coffee (C. liberica var. liberica) and excelsa coffee (C. liberica var. dewevrei), represents a minor share of global production, although the cultivation of this species is steadily increasing owing to climate challenges affecting Arabica and robusta, coupled with an increasing market demand². In Southeast Asia, Liberica consumption has continued since its introduction in the late-nineteenth century and is now witnessing a renaissance, particularly in Malaysia, Indonesia and Fiji. In Uganda, South Sudan and Guinea, attention is focused on excelsa owing to its ability to grow and produce commercially viable crops under higher temperatures and extended periods of low rainfall compared with robusta^2,3. Excelsa production is also increasing in India in response to worsening climate conditions for Arabica and robusta, and in Vietnam and Indonesia to supplement robusta and diversify coffee production. Here we investigate species delimitation in C. liberica using genomic data in combination with morphology and geographical distribution, to understand the implications for coffee crop improvement and the conservation of coffee genetic resources.