Raster image files from circular trees in R

There is some noticeable aliasing in circular (type="fan") trees exported directly from R in a raster format such as .png or .jpg. This can be overcome by exporting instead in a lossless vector format such as .pdf or .eps.

For example, here is a circular contMap style tree exported from R as a .png:

(Click for highest resolution version.)

Whereas here is the same tree exported as a .pdf, then read into Illustrator & exported as a much higher quality .jpg (a raster graphic format):

(Click for highest resolution version.)