Figure 2

Phylogeny of Zingiberales with key events in androecial evolution. (A) Morphological character states of the androecium are mapped onto the most recent Zingiberales phylogeny [28]. The eight Zingiberales families are divided into two groups: the first diverging banana lineages (Heliconiaceae, Strelitziaceae, Musaceae, and Lowiaceae), and the derived ginger clade (Zingiberaceae, Costaceae, Marantaceae, and Cannaceae). Main changes in androecial morphology are depicted with numbers. (1) Reduction in the number of fertile stamens, from 5 to 6 fertile stamens in the banana lineages, to 1 fertile stamen in Zingiberaceae and Costaceae or ½ of a fertile stamen in Marantaceae and Cannaceae; (2) fusion of petaloid staminodes leading to the formation of the labellum. Five infertile stamens fuse in Costaceae, while 2 or 4 staminodes form the labellum in the Zingiberaceae; (3) laminar extension of the filament of the fertile stamen; (4) abortion of a theca of fertile stamen. (B) Costus sp. flowers. (La) labellum; Asterisk indicates the abaxial side of laminar connective of fertile stamen. (C) Canna indica one half fertile stamen. (Th) single theca; (Pa) petaloid appendage resulting from the laminar expansion of the filament [29].