2.1 Plant material
In the summer of 2020, A. cantabrica populations were sampled from six locations that collectively represent its distribution range, as illustrated in Fig. 2A. Within these populations, its distribution is often fragmented, resulting in multiple subpopulations, notably in Tres Meras (TM). A total of thirty-five individuals were collected, with six individuals sampled from each population, except for Hoya Continua (HC), where only one individual was available for analysis. Three additional individuals were sampled from different subpopulations within TM, along with one more from a separate Valdecebollas (VB) subpopulation. Related taxa of A. cantabrica from the northern Iberian Peninsula were also sampled, including six individuals from an A. halleri subsp. nuria Schönsw. & Schneew. population (Fig. 2B; Suppl. Table 1). Fresh leaf tissue samples were dried in silica gel, and specimen vouchers were preserved at the JACA Herbarium (Suppl. Table 1). Specimens from the four Alps taxa were obtained from the Kew Herbarium (Suppl. Fig. 1), with additional sequencing data sourced for related taxa and Primula matthioli (L.) V.A.Richt. which was selected as an outgroup (Suppl. Table 2). Field sampling also involved recording population sizes, key reproductive traits, and the conservation status of each population. We further reassessed the IUCN category following the standards set by the IUCN Species Survival Commission (2012).