M. S., Ph.D.
Hi There!This site is out of date. Please head over to: jwiggi18.github.io/ to see what I'm up to these days.
The Evolutionary Ecology of Color
Why Dichromatic Color in a Juvenile?
Why a conspicuous color signal in a juvenile?
A juvenile male Crotaphytus collaris is pictured above. This male is displaying the conspicuous coloration (hatchling orange bars; HOB) that is the focus of my current work.
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Many animals display conspicuous coloration. Birds often come to mind as excellent examples, the male peacock is particularly well adorned. In most cases this coloration is a substrate for sexual selection. Meaning that the coloration promotes the possessor's increased contribution of his or her genes to subsequent generations directly through increased mating success. Natural selection is a broader category in which sexual selection is nested. Traits selected for by natural selection also increase gene contribution in future generations but can accomplish this through methods other than increased mating success.
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The significance of this coloration in C. collaris is that it occurs prior to sexual maturity, at a time when most species are doing their best to blend in with the background. So why are pre-reproductive male C. collaris advertising their presence?
That is the question!
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We are coming at it from a number of angles, described below, enjoy!
Of all the approaches we are currently using to analyze this signal this is by far my favorite (don't tell the others). I love all things genetics. I'm constantly amazed by how much information we can glean from a little blood, or saliva, or hair... or heck the water an animal swam in!
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For my project I am using nine microsatellite markers to determine the level of structure in my population and subsequently assign parentage to all individuals in the population. I am then using those data to determine if four color variables (described below) correlate with the bearer's fitness.
Genetics
Color Measurement
Everything really centers around knowing what is going on with this color that the males are displaying (even my precious genetics). For each hatchling I measure four color variables, three by spectrometry (Hue, Saturation, and Brightness) and the fourth is a measurement of total area of orange. ​
Hormones
We are also working to determine if different levels of sex steroids (Testosterone, Dihydrotestosterone, Progesterone, and Estradiol) correlate with the appearance, disappearance, or color variables of the hatchling orange bars. We are determining plasma hormone levels using radioimmunoassay (RIA).
Immunology
It is believed, and has been demonstrated in some species, that the bearer of conspicuous signals suffers immunological costs as a result. To test this is C. collaris we cultured subject blood with the bacteria E. coli to determine if lizards with different color values have different bacteria killing capacity.
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Additionally, we are in the process of measuring wound healing in a different subset of individuals to test the same in a different way.
Field
The backbone of this extensive project was the extensive field work that we undertook five months a year. My field site was a mile long stretch of rock dam along the northern edge of Sooner lake in Oklahoma.
We spend roughly five days a week (weather dependent) capturing and marking (with non-toxic latex paint) every lizard on the dam (n ~ 200/year) and subsequently recording location data for each sighting. Additionally, data and blood collection for each of the analyses mentioned above are carried out during the hatchling field season (August - October).
A project of this scope is truly a team effort and I have had the honor of mentoring twenty-one undergraduate volunteers and five field technicians. Please see the "People" page to learn more about our crew!