A very helpful self-taught (in his own words) botanist now living in Tasmania, nuytsia (who blogs on a lot more than just botany), has sent along some nice additional information on Lantana and we have had some correspondence about it. With his permission, I’m quoting him here.
About nectar robbery:
…you say “the stingless bee Trigona fulviventris bites holes in the bases of the stamens of L. camara and robs nectar without performing pollination.” Is that right or should it be corollas?
The quote was from the original scientific paper, and he checked that out first. Then he found the explanation:
Aaaah! (Just checked DELTA) [DELTA is an online interactive key for identifying plants. It includes descriptions of families and lists of genera within each family, among many other helpful aids.]
In Verbenaceae the stamens are placed on the corolla tube so if you’re biting “holes below the base of the stamens” you are biting through the corolla I guess.
So technically it’s right, but a bit confusing.
…
Such “robbery” is observed in bumblebees in the UK on a number of plant species where they don’t “fit” the flower. The protective ring is an interesting concept and one I’ll bear in mind when looking at other plants.
We then had a discussion about flower color – why yellow and red? Does the yellow tell the butterfly to get the nectar “here” and does the red tell the butterfly “don’t bother?”
I think you’re almost certainly correct. Changes in flower colour are common in some of the herbaceous Boraginaceae. [The Borage or Forget-me-not family.]
I’ve done a little searching myself and found two more tantillising JSTOR refs!
This article talks about the evolution of flower colour change in Fuchsia exocorticata. The plant has delayed the development of mature red flower colour to
make them easier to spot for the bird pollinator.This article is rather nice explanantion as to why the flowers might persist in a different colour rather than just wither straight after pollination. It makes the
infloresence bigger and more obvious.
I was also interested in how quickly the flower changes color. The article that started this discussion on nectar robbery mentioned that newly opened flowers are yellow and begin turning orange within 9 hours. One corollary is that the yellow flowers have mostly lost their nectar within that 9 hours.
I checked my plants this morning. As I mentioned to Andee in my reply to her comment on the original Lantana post, these flowers are looking pretty battered at this point in the rainy season.
This morning I saw what I thought was a purely red flower. I now know that I was looking at the buds in the center of the flower.
I didn’t take a picture, but when I went back just after noon today, I saw the outer rim had yellow flowers.
The image is a little blurry because the wind was blowing and I just couldn’t make it stop for my photograph.
I just now checked again (it’s a little past 5 PM) and those yellow flowers have deepened to an orange. By tomorrow those flowers should be red and there should be new yellow ones near the center. I can hardly wait!
Oh, I should mention. Australia is one of those places where L. camara is an invasive species. So is Tasmania. Nuytsia’s comment:
Uuuuugggh bad weed, bad weed.
[In a follow-up note, Nuytsia said that actually Lantana has been eradicated as a pest weed in Tasmania, which he finds an impressive feat "...as it's such a wretched thing." ]
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25 October 2006, 09:00
Here’s that same flowerhead this morning. The 7 once-yellow flowers have become orange, 7 buds have opened to become yellow flowers, and the flowerhead itself is somewhat larger in diameter because of the opened flowers. The wilted flowerhead at about 4 o’clock is a little more wilted, and the same color changes have occurred in the other two scraggly flowers.
As a bonus, I watched a wasp-type insect drink nectar from the yellow flowers on a different flowerhead.
Question now is: Is this a thief or a pollinator? Ah, it never ends, does it?
