The asymmetrical inflorescences of Bidens asymmetrica
Bidens asymmetrica, known as Ko’olau Range beggarticks, is endemic to the leeward side of the southeastern Ko’olau Mountains on O’ahu. The species is listed as imperiled, in part due to its restricted range. Plants grow in mid-moisture hardwood forests and woodland areas, typically on slopes or ridges between 300-600m (1000-2000ft.). Ko’olau Range beggarticks bloom in the spring and summer, with small inflorescences that quickly develop into fruit. In cultivation, these plants may bloom year round.
According to the Bishop Museum, 19 species of beggarticks occur on the Hawaiian islands. The group is collectively named ko’oko’olau in Hawaiian. The previous link details traditional uses of the Hawaiian beggarticks, including medical treatment for thrush, fungal diseases, and throat and stomach troubles (as a tea).
The Ko’olau Range, where this species is found, is a remnant of the Ko’olau shield volcano of O’ahu. Only the former western part of the volcano remains, as the eastern half slid into the Pacific Ocean and is spread across the ocean floor. In the millions of years since this event, erosion has shaped what remains. Geological explorers of the mountain range will also encounter xenoliths along with the landscape designated as a US National Natural Landmark.
Poor Thing! I can relate – Bad Hair Friday……
Curious – why evolve to this irregular form? We think of most flowers having a more ‘typical’ shape within their basic arrangement. Can there be any advantage? Thanks David and Daniel
It is curious, isn’t it? I’ll send an email about the species to some of the local experts involved with the Manoa Cliff Restoration Project, and ask them to comment. Definitely worth checking out their site, to get an idea of the associated flora.
Received this reply from Dr. Mashuri Waite:
“Most of the flowers are more or less symmetrical. I had assumed that asymmetrica referred to the seeds. The seeds are somewhat curled, rather than straight, which has been interpreted (for example in Carlquist) to be an adaptation to wind dispersal rather than hooking on to animals for dispersal.”
I’ll try to locate the original paper where the species was described.
Found it. Looks like it is named asymmetrica due to the leaf base, of all things.
See the Latin description for Lipochaeta asymmetrica (its previous name) here: Volume 10 of
Repertorium specierum novarum regni vegetabilis.
“folia…ad basin conspicue asymtreica”, which I interpret as: “Leaves conspicuously asymmetric at base”
Paul Zweng is reforesting his property in Waikane, on the Windward side of Oahu. I volunteered for a short period and helped re-introduce Bidens populifolia (ko’oko’olau) to his valley hillsides. Paul has also done a beautiful job of eradicating invasive trees such as Albizia and Schefflera actinophylla among others. When these upper canopy trees defoliate the native Koa tree seedlings appear. It is so amazing to see these Koa seedlings emerge along with the Biden seedlings. Attached is an image of a group of us planting Biden seeds. I am standing on the left.
Good work, Brynn (and Paul). Thank you!