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Botany Photo of the Day
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Trematolobelia kaalae

Trematolobelia kaalae
Trematolobelia kaalae

Taisha is the author of today's entry. She writes:

Today, we have two photographs of the Hawai'ian Trematolobelia kaalae (photo 1 | photo 2). They were taken by David Eickhoff@Flickr last May, and uploaded to the Botany Photo of the Day Flickr Pool. Thanks David!

Trematolobelia kaalae is endemic to the Wai'anae Mountains of O'ahu. It is perhaps most easily found on the upper slopes and summit of Ka'ala (its namesake), growing in wet shrubland. Plants will grow to about 2 metres in height at maturity. Once mature, plants will blossom from mid-March to late May with pink flowers. Most other members of Campanulaceae (bellflower family) on Hawai'i are autumn-blooming.

Evidence to-date reveals that the Campanulaceae of Hawai'i form the largest plant clade, or the largest grouping of species originating from a single ancestor, of any single oceanic island or archipelago. With 126 species in 6 genera, these Hawaiian endemics (known collectively as the Hawaiian lobeliads) are an example of an impressive adaptive radiation in plants. A recent study suggests that this monophyletic group originated from a single colonization event about 13 million years ago. After colonization, radiation (or diversification into new taxa), began quickly. The first split occurred after only 0.3 million years, and all genera diverged by 9.76 mya based on top-down calibration (6.97 mya for bottom-up calibration). Trematobelia was among the last to diverge (i.e., it is among the most recently-evolved), along with Lobelia sect. Galeatella.

The diversity of the Hawai'ian lobeliads is outstanding across species, including high-elevation bog rosette-forming species, cliff-dwelling succulents, and forest & bog shrubs. Taxa vary widely in leaf and floral morphology as well. Floral diversity is seemingly associated with a species' ability to disperse seed. The lowest overall diversity and percent single-island endemism is found in lineages that are wind-dispersed, including Trematolobelia, while the highest diversity and percent endemism occurs in genera with fleshy fruits that are poorly dispersed by birds, like Cyanea (see: Givnish, T.J., et al. 2009. Origin, adaptive radiation and diversification of the Hawaiian lobeliads (Asterales: Campanulaceae). (PDF) Proc. R. Soc. B 276:407- 416.

For a thorough overview of speciation and adaptive radiation, refer to Givnish's article from 2010, Ecology of plant speciation (PDF), published in Taxon 59(5):1326-1366.

8 Comments

Nadia commented:

So beautiful, no words

Kathy commented:

That's quite spectacular!

What pollinates it?

David Eickhoff commented:

Aloha Kathy,

Re: "What Pollinates it?"

Many of the Hawaiian lobeliads have curved flower corollas which are perfectly designed for their pollinators honeycreepers and honeyeaters. The latter are all now extinct, but included ʻōʻō (Moho spp.) and koiea (Chaetoptila spp.). While some honeycreepers such as ʻapapane (Himatione sanguinea) and ʻamakihi (Hemignathus flavus) were in the area.However, though I have seen ʻamakihi visit the flowers in the past, none were observed pollinating these plants this time.
It is very possible that other native and non-native creatures share in the pollination as well.

To learn more about other Hawaiian lobeliads check out the Native Plants Hawaiʻi website (URL below)

Aloha,
Dave

David W. Eickhoff
Native Hawaiian Plant Specialist
eickhoff@hawaii.edu
808.429.8964
Native Plants Hawai'i
http://www.nativeplants.hawaii.edu

michael aman commented:

It is reminiscent of a dancers headwear above and skirt below

Wouter Bleeker commented:

Very interesting entry!

Note that ~13 million years ago (Ma), the island of Oahu had not yet formed, so this taxon must have originally colonized an earlier, now largely submerged Hawaiian island ~1000 km to the northwest along the island chain.

As these plants evolved and radiated they had to keep colonizing islands that grow by volcanism to the southeast, due to movement of the Pacific plate over the Hawaiian hotspot (~10 cm/yr). Oahu only formed 3-4 Ma. It's a race! And against the prevailing trade winds.

Ron B commented:

Many years ago I hiked north from the top of my grandmother's neighborhood above Kaimuki and encountered the orange version in bloom just over the north (rainy) side of the summit ridge, way over near the east end, north or northeast of Honolulu - facing north and looking down from among the plants, I could hear dogs and chickens in the neighborhoods below the cliff. There was also Vaccinium and other cloud-land indicators, also apparently on the very edge of their climate tolerances.

Jessica commented:

That is one wild and craaaazy flower and plant.

Gorgeous!

Interesting to see this member of the Campanulaceae. It's one of my favorite groups of flowers. Even our humble garden Bellflowers and Lobelias are soooo lovely.

Donna Brownlee commented:

a beautiful flower! does anyone else see the trematodes in the flower?

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