Thursday, May 5, 2016

Variation in phenotype (mutants!)

Obviously, variation in traits is present in all populations and all species, but its quite easy to forget that - a mallard looks like a mallard, right? Evolution acts upon this variation, be it timing of flowering, anti-predator behavior or body size, constantly. I find variation in "characteristic" traits very interesting (and by "characteristic", I mean how a naturalist would recognize a species, for instance in plants this might be color, growth form, leaf shape, etc.). I've been noting these for quite awhile and keeping a photo log - mostly of flower color, which is especially interesting to me - here's a selection.

This isn't meant as a real ecology post, just an appreciation for the natural world, but do bear in mind the little tidbits of science thrown in - they'll only make it more interesting. As Huxley famously said, "To the person uninstructed in natural history, his country or sea-side stroll is a walk through a gallery filled with wonderful works of art, nine-tenths of which have their faces turned to the wall."

I'll mostly put a "normal" picture first and then the mutant. Here's a normal Mimulus guttatus, the common yellow monkeyflower - a widespread, common and lovely species.

McLaughlin Reserve, Lake County, CA. 
And a weird red mutant:

McLaughlin Reserve, Lake County, CA
A normal Tritelia laxa.

Berryessa-Knoxville Rd., Napa County, CA
And a white one:

Berryessa-Knoxville Rd., Napa County, CA
A normal blue-eyed "grass" (really an iris), Sisyrinchium bellum:

McLaughlin Reserve, Lake County, CA

and a white one:
McLaughlin Reserve, Lake County, CA
Normal Mimulus nudatus, a cool serpentine endemic in the northern coast range.

McLaughlin Reserve, Lake County, CA
And a weird beige morph:

McLaughlin Reserve, Lake County, CA
And both normal and white morphs of Collinsia sparsiflora:

McLaughlin Reserve, Napa County, CA
Normal and white morphs of Mimulus layneae. Interestingly, the two white individuals in this population had flatter flowers as well.

McLaughlin Reserve, Lake County, CA
Why are white flowers so common in plants? Purple or reddish colors are caused by a group of chemicals called anthocyanins. These are synthesized in a pretty complex pathway that involves a bunch of steps, all mediated by proteins. If a mutation (or developmental issue), interrupts the function of any of these steps, you get a loss of function, which in this case becomes a white flower.

In some species, there is simply a polymorphism - its not rare to have differently-colored flowers (or -colored seed, or -shaped fruit, etc.). This Leptosiphon sp. has both pink and white flowers in roughly equal proportions in a population I looked at.

McLaughlin Reserve, Lake County, CA

Like Leptosiphon, many other members of the Polemoniaceae have white/colored polymorphisms within populations. Navarretia mellita (often a sandy plant!), is one:

McLaughlin Reserve, Lake County, CA

McLaughlin Reserve, Lake County, CA

Of course, color polymorphisms aren't restricted to flowers, or even plants. A cool hypothesis to explain the existance of color polymorphisms in many species of raptors is that it is harder for prey to figure out what is a predator if they all look different. To the best of my knowledge, that hypothesis is still up for debate, but its clever and seems logical. Here is a pair of Variable Hawks, Buteo polyosoma:

Bosque del Pomac, Lambayeque, Peru
And another morph, of the same species!

A juvenile, I think. Bosque del Pomac, Lambayeque, Peru
I don't know any hypotheses for the maintenance of color polymorphisms in caterpillars, but some have them. Hyles lineata feeding on Abronia villosa:

San Diego Co., CA

San Diego Co., CA

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