I am currently at the annual meeting for the Society for Integrative and Comparative biology in Portland, Oregon. This has been a great meeting so far, where I have met potential collaborators and future post-doc advisors (fingers crossed!). I’ll blog more about the meeting later, but I’ll briefly cover what I came here to talk about.
I gave a talk today on the evolution of hummingbird coloration across 250+ species. I used images from Handbook of Birds of the World to gather the color data and did a variety of analyses. Here are a few of the results I presented (remember these are still very preliminary!) I reconstructed the evolution of different color patches such as the gorget, crown, or back.
This is a circular phylogeny of hummingbirds, with the evolution of their gorget (throat patch) coloration mapped onto it. A phylogeny is a reconstruction of the evolutionary relationships between species across time. The middle of the image represents the most common ancestor of all hummingbirds and each of the tips of the tree represent the exact species. The lines connecting all of the species are showing not only the relationships between them, but also how long it was before different species diverged from each other. The color of the lines represent the estimated throat color of the ancestor at that given time, and the colored circles (which are pie-charts) represent the probability of the ancestor at a connection/split between two lines being a given color.
I reconstructed the evolution of sexual dichromatism (differences in coloration between males and females).
Here is another circular phylogeny, which is based on the same principles of the previous image, but with a different trait mapped onto it. Here I have mapped on the evolution of sexual differences in coloration (sexual dichromatism). Cooler colors mean greater differences between the coloration of males and females, while warmer colors mean less differences between male and female coloration. Red means that there are no differences in sexual dichromatism (both sexes look the same). The bars at the end of each tip represent the sexual dichromatism value for each extant species, with larger bars showing greater differences in sexual dichromatism.
I compared the evolution of some color patches other color patches.
These are phylogenetically controlled regressions between gorget color and forehead color. Basically, theses are normal regressions that take into account the evolutionary history between the species. Each point on the graphs has two colors – the top square is the color of the male’s forehead, while the bottom square is the color oft he male’s gorget. I compared the evolution of male gorget and forehead hue, saturation and brightness, which are three quantitative ways of describing color. Hue is what we traditionally think of when we say color (e.g. red, green, blue); saturation is how pure that color is (e.g. deep blue vs. washed out blue); and brightness is how light or dark the color is (e.g. white vs. grey vs. black). There is a significant relationship between the evolution of gorget hue and forehead hue, meaning that species with particular gorget hues (e.g. red) have similar forehead hues. There was also a significant relationship between gorget and forehead brightness, meaning that species with brighter gorgets have brighter foreheads. There was no relationship between gorget and forehead saturation.
And finally, I started comparing different color patches to some environmental variables (no relationships found yet). All of what I presented are preliminary results, because I am just starting to dive into this dataset, but it was a great opportunity for me to get my name out there, meet some awesome people, and get some good feedback. I hope everyone else at this meeting had a great time, and I look forward to the last day of talks!