AUTHOR=Iwamoto Akitoshi , Ishigooka Shiori , Cao Limin , Ronse De Craene Louis P. 

TITLE=Floral Development Reveals the Existence of a Fifth Staminode on the Labellum of Basal Globbeae

JOURNAL=Frontiers in Ecology and Evolution

VOLUME=8

YEAR=2020

URL=https://www.frontiersin.org/journals/ecology-and-evolution/articles/10.3389/fevo.2020.00133

DOI=10.3389/fevo.2020.00133

ISSN=2296-701X

ABSTRACT=<p>We observed the floral development of <italic>Hemiorchis burmanica</italic> and two species of <italic>Gagnepainia</italic>, which make up the sister group of <italic>Globba</italic> in Globbeae, as well as a selected number of species of <italic>Globba</italic>. Our observations revealed that in <italic>Gagnepainia</italic>, a “fifth staminode,” develops as part of the labellum, while it is generally lost in other Zingiberaceae. The fifth staminode, however, was not initiated in the labellum of <italic>Hemiorchis.</italic> A fifth staminode was also observed in <italic>Globba geoffrayi</italic> but was not found in all other species of <italic>Globba</italic> investigated. While the staminode becomes an integral part of the labellum in <italic>Gagnepainia</italic>, it remains small and almost aborts at later stages of development in <italic>G. geoffrayi</italic>. These results indicate that the development of a fifth staminode could be a recurring plesiomorphic trait for Globbeae, only retained in <italic>G. geoffrayi</italic>. The retention of the fifth staminode and its heterochronic shift may be linked with the mechanical constriction within the flower bud. The results may also support the interpretation of an atavistic expression of a once lost staminode.</p>