Different clades, different changes: karyotype evolution in Convolvulaceae, with emphasis on <i>Jacquemontia</i> and the phylogenetic placement of <i>Daustinia montana</i>

Abstract Convolvulaceae comprises ∼2000 species worldwide, but cytogenetic information remains scarce for several lineages. Here, we present a comparative karyotype analysis of Jacquemontia and Daustinia montana, the focal genera of this study, which share a history of taxonomic uncertainty and form a dysploid series that brings the phylogenetic placement of D. montana into focus, while also incorporating cytological comparisons with Dinetus racemosus and Ipomoea to contextualize broader patterns within Convolvulaceae. We combined chromosome counts, CMA/DAPI banding, and genome size estimates to investigate how dysploidy and polyploidy contribute to karyotype diversification in these lineages. Novel CMA/DAPI banding patterns were characterized for D. montana and five species of Jacquemontia. Chromosome numbers ranged from 2n = 16 in D. montana to 2n = 36 in J. mucronifera and J. pentanthos. All species exhibited terminal CMA+ bands, while DAPI + heterochromatin was exclusive to Jacquemontia. Genome sizes varied 2.5-fold, from 1C = 0.90 pg in D. montana to 1C = 2.32 pg in J. mucronifera. Probabilistic analyses support x = 14 as the basic chromosome number for Convolvulaceae and Dicranostyloideae. Our results show that although dysploidy underlies major differences between the two genera, both dysploidy and polyploidy have shaped karyotype evolution within Jacquemontia. The karyotypic affinities observed among Daustinia, Jacquemontia, and Dinetus provide new cytological evidence relevant to the phylogenetic position of D. montana.