Karyotype asymmetry shapes diversity within the physaloids (Physalidinae, Physalideae, Solanaceae)

Abstract

Within the cosmopolitan family Solanaceae, Physalideae is the tribe with the highest generic diversity (30 genera and more than 200 species). This tribe embraces subtribe Physalidinae, in which positions of some genera are not entirely resolved. Chromosomes may help on this goal, by providing information on the processes underlying speciation. Thus, cytogenetic analyses were carried out in the subtribe in order to establish its chromosome number and morphology. Physalidinae is characterized by x = 12 and most species shows a highly asymmetric karyotype. These karyotype traits were mapped onto a molecular phylogeny to test the congruence between karyotype evolution and clade differentiation. A diploid ancestor was reconstructed for the subtribe, and five to six polyploidy independent events were estimated, plus one aneuploidy event (X = 11 in the monotypic genus Quincula). Comparative phylogenetic methods showed that asymmetry indices and chromosome arm ratio (r) have a high phylogenetic signal, whereas the number of telocentric and submetacentric chromosomes presented a conspicuous amount of changes. Karyotype asymmetry allow us to differentiate genera within the subtribe. Overall, our study suggests that Physalidineae diversification has been accompanied by karyotype changes, which can be applied to delimit genera within the group.