Let’s talk about: ‘Oha

Today’s post I thought I’d talk more in detail about Delissea. I want to get into a bit of it’s natural history, the grave challenges it faces but also some unique opportunities that anyone of interest can engage with.

Of the Hawaiian lobeliads, originally there were thought to be about 15 different species of ‘Oha (Delissea spp) endemic to the archipelago. They were typically found in dry-mesic forests throughout the chain; there was even a populations once found on the island of Ni’ihau. With its branched habit, orthophilous flowers and baccate fruit, one would think Delissea are closely related to the similar looking Cyanea. It wouldn’t be surprising to think that they were just offshoots of the great Cyanea radiation of wet forests that invaded drier habitats. But the genetic work seems to show something that I find far more interesting.

Genetic work by Givnish, 2008 and Hunter (unpublished) both corroborate a strong relationship between Delissea and Brighamia. And both seem to nest within the overall radiation of sect. Galeatella, Trematolobelia, and sect. Revolutella, though with weak support. So there is a chance that within the greater Hawaiian lobeliad lineage, there are 2 parallel radiations of iteroparous, branching shrubs with axilliary flowers and baccate fruit. One in wet forests and one in dry. While that may seem like strange coincidence it may show just how much selective pressure the native forests birds of Hawai’i were once putting on the plants of the forests. Nectivorous and frugivorous birds would have been found in all sorts of habitats, regardless of the rainfall gradient. The plants would have been responding to similar pressures from the birds, and in this case coming up with very similar solutions.

As neat as the evolutionary history of Delissea is, the group as a whole has not fared well in the face of anthropogenic change. Hawaiian lobeliads in general have been fairly sensitive to the damages humans have wrought but none more so than all the Delissea spp. Their dry forest habitats are some of the most extensively modified in the chain. Indeed, a majority of the human population in Hawai’i lives in former dry forests and coastal strand habitat, to the detriment of native biota. Of all the species, only Delissea rhytidosperma, D. kauaiensis, D. waianaeensis, & D. argutidentata are known to survive.

As sad as that is, oddly enough it provides a strange opportunity. If you live on Kaua’i, O’ahu or Hawai’i island, odds are you live in former Delissea habitat. And it turns out Delissea can be a surprisingly decent houseplants. The picture above are the Delissea next to me as I type this. I’m like one of those chefs that does take out at home. I work with plants for work. I work with plants for restoration. The last thing I want to do is take care of plants when I get home đŸ˜› The point being, these plants do well even with my relative lack of attention. I just try to make sure to keep up with their eternal enemies: spider mites.

Will Delissea invade that new habitat call Instagram? Who knows. But the fact that they can reclaim old territory while paradoxically adapting to new habitat (indoor life) at the same time is the type of Sharing the Planet that I find so appealing. Delissea, the Cyanea analogue unique to Hawaiian dry forests, once on the brink but now primed to push out your chia pet!

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