Joined: Jan. 2006
What's a "more complex species"? One that has a bigger genome? Polyploidization produces those species all the time.
On the top of my head, I cannot find pairs of incipient species where one could be readily considered phenotypically as "more complex". New functions, like new organs, take some time to evolve, and that is not achieved through a single speciation event. Of course, difference in phenotypic complexity is visible when you compare more distant species. Some Heliconius races have complex wing patterns that are derived from simpler patterns (if I'm not mistaken). Does that count?