The role of chromosome changes in the diversification of <i>Passiflora</i> L. (Passifloraceae)

<i>Passiflora</i> L. has more than 575 species distributed especially in the Neotropics. The chromosome number variation in the genus is highly congruent with its main subgenera, but its basic chromosome number (<i>x</i>) and the underlying events responsible for this variation have remained controversial. Here, we provide a robust and well-resolved time-calibrated phylogeny that includes 102 taxa, and by means of phylogenetic comparative methods (PCM) we tested the relative importance of polyploidy and dysploidy events to <i>Passiflora</i> karyotype evolution and diversification. <i>Passiflora</i> arose 42.9 Mya, with subgenus diversification at the end of the Palaeogene (Eocene-Oligocene). The basic chromosome number of the genus is proposed as <i>x</i> = 6, and a strong recent diversification found in the <i>Passiflora</i> subgenus (Miocene) correlated to genome size increase and a chromosome change from <i>n</i> = 6 to <i>n</i> = 9 by ascending dysploidy. Polyploidy, conversely, appeared restricted to few lineages, such as <i>Astrophea</i> and <i>Deidamioides</i> subgenera, and did not lead to diversification increases. Our findings suggest that ascending dysploidy provided a great advantage for generating long-term persistent lineages and promoting species diversification. Thus, chromosome numbers/genome size changes may have contributed to morphological/ecological traits that explain the pattern of diversification observed in the genus <i>Passiflora</i>.