Phylogenetic relationships and chromosomal evolution in <i>Exodeconus</i> (Solanaceae), ephemerals from the west coast of South America

Abstract Exodeconus is a small Andean genus of Solanaceae comprising six poorly known species of ephemeral plants, which are found in diverse environments from sea level to ca. 3500 m. This study aims to investigate the evolutionary history of the genus following an integrative approach, combining molecular phylogenetics, cytogenetics, and distribution data, and to formally describe a new species from southern Peru, E. minutiflorus . Species distribution ranges are updated following exhaustive compilation and curation of existing collection data. Phylogenetic analyses support the monophyly of Exodeconus , whose species are resolved in three well‐supported lineages that closely correspond to geographic and elevational patterns: E. integrifolius , recovered as sister to the rest of the genus; the sister species E. maritimus and E. miersii splitting next; and a third lineage encompassing E. prostratus , E. flavus , E. minutiflorus and E. pusillus . For the first time, chromosome numbers are reported for the whole genus (2 n = 24), while all evaluated samples exhibit distinguishable karyotype features that help to improve species delimitation. Ancestral state reconstruction of chromosomal traits evidenced a trend towards increased karyotype symmetry and inferred the most recent common ancestor of Exodeconus to most likely have an asymmetric karyotype with four metacentric chromosomes, seven submetacentric chromosomes, one subtelocentric chromosome per haploid complement, and a single nucleolar organizer region (NOR) located on a submetacentric chromosome. This study provides new insights into the evolution of Exodeconus , contributes to clarify species boundaries and distribution, and offers robust evidence supporting the recognition of E. minutiflorus as a new species.