Divergent genome sizes reflect the infrafamilial subdivision of the neotropical woody M arcgraviaceae

Neotropical M arcgraviaceae comprise about seven genera and 130 species of lianas and shrubs. They predominantly occur in lowland or montane rainforests and are characterized by a variety of pollination systems. Early classifications subdivided M arcgraviaceae into subfamilies M arcgravioideae and N oranteoideae, a concept supported by molecular data. Using flow cytometry and chromosome numbers, we investigated the role of genome size and polyploidization in the evolution of M arcgraviaceae and how genome sizes are distributed between the proposed infrafamilial groups. To do this we determined genome sizes and chromosome counts for six genera and 22 species for the first time. Our study supports the subfamilial classification of the family, revealing contrasting genome sizes in N oranteoideae ( 2C  = 5.5–21.5 pg) and M arcgravioideae ( 2C  = 2.3–6.2 pg). Polyploidy is considered to be the main source of genome size variation as in each subfamily the higher nuclear DNA amounts were associated with higher ploidy. In addition, genome size changes independent of polyploidy were also observed in some genera, suggesting an additional role for changes in repetitive DNA abundance in the evolution of M arcgraviaceae. A high chromosome base number ( x  = 18; 2 n  = 36 to ∼70) points to an undetected lower diploid level or to palaeopolyploidy. M arcgraviaceae show a remarkable (nine‐fold) variation in genome size, and several N oranteoideae have genome sizes among the highest reported for tropical woody angiosperms worldwide. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society , 2015, 177 , 1–14.