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UltravioletPhotography

Coreopsis tinctoria [Golden Tickseed]


JCDowdy

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Dowdy, J.C. (2014) Coreopsis tinctoria Nutt. (Asteraceae) Golden Tickseed. Photographed in visible and ultraviolet. http://www.ultraviol...olden-tickseed/

 

Other Common Names

Plains coreopsis, Golden tickseed, Goldenwave or Calliopsis

 

Location/Date

Cordova, Tennessee, USA

06 June 2014

Wild along roadside ditch bank

 

Comment/Discussion

Quite lively and complex in visible light but lacking a comparably striking UV signature this ~4cm diameter specimin was rendered generally dark in UV. It is noted however that, "Its tubal disk flowers show a UV-bright corolla edge and the disk anthers are also UV-bright" (Blum, A.G.)

 

post-24-0-14201200-1402362665.jpg

Visible light, photographed in full sunlight.

Panasonic DMC-G3 full spectrum modified, UKA UV 50mm f/3.5, 1/15 sec, ISO 160 & f/11, 1.25” Baader UV/IR cut filter mounted in adapter proximal to sensor.

Custom in camera white balance on PTFE lens cap. In camera JPEG cropped to 1000 pixels wide and auto adjusted for contrast and brightness in ImageJ.

(Image Reference: JCD140606_Coreopsis_tinctoria_VISb.jpg)

 

post-24-0-27571900-1402362709.jpg

Ultraviolet, photographed in full sunlight.

Panasonic DMC-G3 full spectrum modified, UKA UV 50mm f/3.5, 1.3 sec, ISO 160 & f/11, reversed 1.25” Baader U-filter mounted in adapter proximal to sensor.

Custom in camera white balance on PTFE lens cap. In camera JPEG cropped to 1000 pixels wide and auto adjusted for contrast and brightness in ImageJ.

(Image Reference: JCD140606_Coreopsis_tinctoria_UVb.jpg)

 

 

References

 

1. USDA, Natural Resources Conservation Service, The PLANTS Database.(06Jun14) Coreopsis tinctoria. National Plant Data Team, Greensboro, NC USA.

 

2. Lady Bird Johnson Wildflower Center, NPIN: Native Plant Database (06 June 2014) Coreopsis tinctoria. U. of Texas at Austin, Austin, TX USA.

 

13Aug14: Correction to shutter speed Vis & UV.

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John, be sure to add the botanical authority associated with each species.

For your flower that would be Nuttall, so you would write Coreopsis tinctoria Nutt.

 

Yellow is a difficult colour to represent in flower photographs. To bring out a bit more surface detail in the petals, try cutting the yellow contrast and/or saturation just a bit. For the record, I note that the Photo Ninja Detail slider helps delineate surface features when judiciously applied.

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igoriginal

I notice that this pattern is quite common, and consistent across the Coreopsis genera.

 

That is to say, that they seem to be doing the opposite of many other flowers: A solid and featureless UV-absorptive appearance, in UV. And yet, a centralized and conspicuous marking which stands out, when viewed within the visible bandwidth?

 

What's going on, here?

 

Perhaps some flowers evolved to attract mammals, too?

 

(Makes me also wonder how this flower would appear in IR.)

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It is always perilous to extrapolate beyond the domain of existing data set ...

 

Two points come to mind. Firstly, other Coreopsis species do exhibit a different UV signature. Thus, C. bigelovi has the bull's-eye appearance, C. californica has an extended bull's-eye pattern extending almost to the tip of its rays, and C. verticillata is moderately UV-grey all over the ligules. Secondly, the presence of conical cells will turn even UV-dark or near UV-black flower parts into a shimmering display due to iridescence.

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igoriginal

Aha.

 

Thank you for answering this, Bjørn! I knew someone would have the answer. :)

 

So, my experience with the Coreopsis genera is limited, thus far. Even as I have viewed UV patterns of at least 7 different species / cultivars, of which all have exhibited the same, solid-UV properties.

 

The next question I have would be: *Why* would a particular flower species evolve to display a whole-flower UV-absorptive scheme that extents outside of what existing patterns are seen in the visible bandwidth? Even as some of its other siblings within the same genera have not?

 

In other words: Why are such closedly-related species doing completely different things with their UV signatures?

 

Perhaps simply because we are just seeing the various mutations and their divergences within evolution, in-progress?

 

And if so, then I suppose "natural selection" - in due time - will eventually play a role in choosing which presentation would be the most effective in attracting pollinating beneficiaries?

 

But, if that be the case .... then we most likely won't be around, when the "most successful design" finally prevails, amid the "sibling rivalry." As this process typically can occur over hundreds of thousands, if not millions of years.

 

Just some thoughts. I know that I am asking a lot of questions, but all of these observations have me thinking about the "why's" of everything.

 

Thanks again!

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There are other genera in which closely related species can have completely different UV signatures. One example that springs to mind is Erysimum in the Brassicaceae. We observe at present the differences, but lack the understanding why this is so.

 

Speciation is a process that can go fairly quickly so significant differences between taxa can occur in less than a millennium. We see this process is active in regions which were freed of their ice sheets a few thousand years ago.

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igoriginal

Very interesting.

 

Yes, I assumed that this phenomenon was not solely restricted to Coreopsis, but is evident in many other genera.

 

So, until or unless we have more information, then it remains speculation, at best.

 

However, I suppose there would be no harm to propose the hypothesis, in the meantime (based on existing empirical knowledge) that we may simply be witnessing Darwinian "national selection", in comparative progress. A sort of "casting call" or "audition for best parts", via mutation rivalry.

 

That is the only feasible explanation that I can come by, anyway. But, then, I am sure there may be other matters at work here, including localized environmantal stressors which effect closely-related species just slightly differently enough to sometimes manifest physically-observable variations.

 

Of course, what we DO NOT know is which specific stressors correlate to each specific physical variation. And ... we may NEVER know, because no single human lives long enough (nor is present everywhere at the same time) to sit and watch this process unfold in its entirety while being able to take every tiny and subtle environmental stressor into account.

 

We are not omnipotent and omnipresent, after all. :)

 

(Which is precisely why there will always be a disproportionate amount of "how's" answered in the sciences, compared to "why's.")

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Sometimes there is as yet unrecognized species differentiation which might be indicated by differences in UV signature. Bjørn and I observed two different UV signature types in our Hieracium - one subset of which was later reassigned to species Pilosella.

 

Hieracium kalmii having UV-dark bullseye:

http://www.ultraviol...__fromsearch__1

 

Pilosella peleteriana (formerly Hieracium) uniformly dark in UV:

http://www.ultraviol...__fromsearch__1

 

Added: I note for the record that I am just speculating. One observation does not a hypothesis make.

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igoriginal

Very fascinating, Andrea!

 

Thanks for sharing!

 

Yes, that is a great insight, on your part. I forget the fact that species are often renamed and reclassified, within the field of botany, as new / additional information is derived.

 

So, perhaps any significant variations in UV signatures may (one day) become yet another parameter for judging a potential species separation / reclassification, within the field of botany? Meaning, become yet another recognized standard for testing and determining classification?

 

Perhaps the work done by us UV photographers will eventually pose much more influential implications within the field of botany, in the future, concerning how classifications are judged, determined, and placed.

 

Hmmm.

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As Bjørn once observed: Scientists are usually not good photographers and photographers are usually not good scientists.

 

So maybe our UV signatures database will eventually be useful to researchers. Wouldn't that be a nice thing?

 

As UV photographers we are not at all in a position to perform any serious botanical lab experiments or studies, so we just concentrate on the UV photography. And occasionally make note of some interesting phenomena like what we saw in the Hieracium/Pilosella.

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John, in addition to the preceding comment (about including the plant author) I wanted to note that your Coreopsis is not devoid of UV "pattern". Its tubal disk flowers show a UV-bright corolla edge and the disk anthers are also UV-bright.
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igoriginal

Coreopsis is not devoid of UV "pattern". Its tubal disk flowers show a UV-bright corolla edge and the disk anthers are also UV-bright.

 

Ahhh. So, in a way, it's kind of like a "reverse" nectar guide. Like swapping the black & white checkerboard patterns on a chess board. The normally UV-dark "bull's eye" here has been inverted into a "ring" instead, so to speak ...and likewise, the normally outer-most UV-reflective border has been pushed into the bull's eye.

 

I know my imagery is somewhat whimsical, but that's what came to mind. :)

 

(Not being literal, just stating it in a metaphorical way.)

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John,

 

Thank you for showing me that I'm not the only person in the world whose visible yellow flowers become UV-dark or even black. I have found a few visible yellow flowers which show a dark central bullseye in UV-yellow petals but then I find visible yellow petals which turn out UV-ace-of-spades black. I'm tending towards those authors who imply that UV response by itself may have been over-hyped.

 

Dave

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Thank you all for your kind comments and helpful corrections on my first formal posting.

It has been noted that a Fierce Bear once opined,

"Scientists are usually not good photographers and photographers are usually not good scientists".

As to the former, in this company I aspire to yet become a good photographer.

To the latter I shall humbly plead that while I am a scientist I am not a botanist.

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John, be sure to add the botanical authority associated with each species.

For your flower that would be Nuttall, so you would write Coreopsis tinctoria Nutt.

 

Yellow is a difficult colour to represent in flower photographs. To bring out a bit more surface detail in the petals, try cutting the yellow contrast and/or saturation just a bit. For the record, I note that the Photo Ninja Detail slider helps delineate surface features when judiciously applied.

Corrections to nomenclature and your comment UV description added.

Both images are now also revised as they were over processed.

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