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

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. 3,500 m. This study aims to investigate the evolutionary history of the genus following an integrative approach, combining molecular phylogenetics, cytogenetics, and distribution data. 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 altitudinal 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 the remaining species and three unidentified accessions. Chromosome numbers are reported here for the first time for E. flavus , E. integrifolius , E. maritimu s, E. prostratus , and E. pusillus (2 n  = 24). All evaluated samples exhibit distinguishable karyotype features that help to improve species delimitation. Ancestral state reconstruction of chromosomal traits evidences 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 NOR located on a submetacentric chromosome. This study provides new insights into the evolution of Exodeconus , contributes to clarify species boundaries and distribution, and provides further evidence for the recognition of a possible new species. A comprehensive taxonomic revision of the genus will still be needed to fully resolve its systematics.