Change of Fate and Staminodial Laminarity as Potential Agents of Floral Diversification in the Zingiberales

The evolution of floral morphology in the monocot order Zingiberales shows a trend in which androecial whorl organs are progressively modified into variously conspicuous “petaloid” structures with differing degrees of fertility. Petaloidy of androecial members results from extensive laminarization of an otherwise radially symmetric structure. The genetic basis of the laminarization of androecial members has been addressed through recent candidate gene studies focused on understanding the spatiotemporal expression patterns of genes known to be necessary to floral organ formation. Here, we explore the correlation between gene duplication events and floral and inflorescence morphological diversification across the Zingiberales by inferring ancestral character states and gene copy number using the most widely accepted phylogenetic hypotheses. Our results suggest that the duplication and differential loss of GLOBOSA (GLO) copies is correlated with a change in the degree of the laminarization of androecial members. We also find an association with increased diversification in most families. We hypothesize that retention of paralogs in flower development genes could have led to a developmental shift affecting androecial organs with potential adaptive consequences, thus favoring diversification in some lineages but not others.