Continuing the theme of red in nature, today's the turn of plants. As with animals, plants generally show red to be noticed. Probably the most obvious manifestation of this is in flowers; the entire purpose of a flower is to attract a pollinator, which is then persuaded by means of a bribe - usually an energy hit in the form of sugar, ie nectar - to venture where it will inadvertently collect pollen to take to another flower. Insects in general see best in the shorter wavelength end of the colour spectrum - blues, purples, yellows - so red flowers are primarily bird-pollinated.
 |
| New Holland Honeyeater Phylidonyris novaehollandiae on Calothamnus sp. Cape Le Grande NP, Western Australia. See pollen all over forehead; the nectary is at the base of the flowers, the pollen is on the feathery red anthers which the bird must push past to claim its treat. |
Australia appears to have an unusually high proportion of bird-pollinated flowers relative to other parts of the world, though work coming out of southern Africa and South America suggests that numbers there are higher than hitherto recognised. Here a few plant families provide a high proportion of bird-pollinated flowers; these are especially Proteaceae, Myrtaceae, Epacridaceae (Australian heaths, sometimes now placed in Ericaceae, the Old World heaths), Fabaceae (peas) and Myoporaceae (mainly Eremophila, though this genus is now sometimes included in Scrophulariaceae). Honeyeaters are by far the major pollinators, followed by the lorikeets, but many other bird families are involved. Here are some examples of the flowers.
 |
| Scarlet Banksia Banksia coccinea, Proteaceae Stirling Ranges NP, Western Australia. |
 |
| Grevillea wickhamii, Proteaceae Bladensburg NP, Queensland. |
 |
| Waratah Telopea speciosissima Proteaceae Carrington Falls, southern New South Wales. |
Proteaceae is an old Gondwanan family, and in South America in particular similar genera occur.
 |
| Notro Embothrium concinnum Proteaceae Laguna Verde, southern Chile. Its main pollinators are hummingbirds and elaenias, generally thought of as flycatchers. |
 |
| Mottlecah, Eucalyptus macrocarpa, Myrtaceae north of Perth, Western Australia. |
 |
| Eremophila glabra Myoporaceae (but see comment above) Shark Bay Western Australia. |
 |
| Running Postman Kennedia prostrata Fabaceae Coffin Bay NP South Australia |
 |
| Epacris longifolia Epacridaceae (but see comment above) Morton NP, New South Wales. |
 |
| Lechanaultia formosa Goodeniaceae Stirling Ranges NP, Western Australia. |
In northern South America hummingbirds dominate pollination and they too are attracted to red.
 |
| Bomeria sp. Alstroemericaceae El Cajas NP, southern Ecuador |
 |
| Fuchsia ampliata Onagraceae Yanacocha Reserve near Quito, Ecuador |
 |
| Epidendrum ardens Orchidaceae Manu National Park southern Peru - 4000 metres above sea level. |
All of this is not of course to say that insects do not visit red flowers - they certainly do.
 |
| Common Crows Euploea core on Callistomen viminalis Undarra NP Queensland |
Whether they respond to scent - not likely, given that birds generally don't rely on it much, unless some red flowers also seek to attract them as a back-up - or simply recognise the flower from other cues, is not known, at least to me.
There are other plant parts that turn red too; I was going to talk about them today, but this has alreddy gone on long enough I think, so I'll pop back tomorrow to finish off.
8 comments:
This is really a thought about the crab. Since the red colour is due to a caretenoid, which I assume is linked to the carotene in our retinal cells, could this been some form of "whole of animal photosensitisation".
Thus rather than being concerned with emitting a message - 'come mate with me' seeming to be the usual decoding - as in birds and flowers it is actually receiving information. Perhaps about water depth?
You asked for ideas, but didn't say they have to be proven (nor sane).
Martin
I think that's brilliant - but we would need to find a mechanism for transmitting the info to the brain for decoding. I'm sure I don't believe it, but... It will probably bother me at 3am tomorrow!
Hmmm...do you know, I am struggling to think of a single truly red flower here, or of any plant that is bird pollinated. Must ask my bird nerd friends. Your post has really brought it home to me.
I was going to add a comment about the insects visiting the callistemon, but found I kept thinking of exceptions to any theory I came up with and was just going round in circles. So, like you, I think it is some visual clue they are responding to, but the flower might be scented. Gosh this fence is uncomfortable...
Well that ties right in with my information, which is that there are indeed no bird-pollinated plants in all of Europe and north Africa; in Asia at equivalent latitudes I understand there are just two, and in North America 8. By contrast at least 1,000 Australian plant species are known to be bird-pollinated.
And no point getting off the fence if neither side of it is offering any evidential reason to do so.
Well one lives and learns (fortunately, failing either of those would be ungood). I rushed off to scan my European Field Guides to Birds and couldn't find a single nectar muncher.
However your reference to North America leads me to ask how you define North America. My (UN driven) view includes Panama and all points North as well as the Caribbean Islands. If that is too extreme I do have trouble excluding Mexico from North America on biogeographical grounds and thought they would have quite a few bird pollinated plants to keep their 50+ species of Hummingbird contented. Even with the US, I know an area in Arizona where 24 species of hummers can be found in a day. Or do the hummers take the nectar with no benefit to the plants?
Martin
Excellent and valid points (as I'd expect!). I totally agree with you re 'North America'; I was scornful and indignant when someone on the ABC recently include Mexico in South America! Unfortunately I no longer have the reference from where I took those figures some time ago, though I recall that it was a serious paper in a peer-reviewed journal. I think the key is in the 'equivalent latitudes', referring to temperate Australia, though I didn't make that clear. How many plants do the 24 Arizonan hummers visit? By the ref I used, it shouldn't be more than 8, but maybe that's out of date and I should update my info! Thanks for prodding me.
I'm unsure about the plants they visit, but am assuming that there must be some in the vicinity as well as the feeders that cheating birders visit. The local cacti should be fair candidates. I will invoke Uncle Google and see what I can dig up.
Martin
Here is a start http://www.fireflyforest.com/flowers/category/hummingbird-flowers-and-plants/
Martin
Post a Comment