I know studies have been done showing the genetic relationships among different centrarchids. But have any studies been done comparing centrarchids to other perciformes?

I was wondering what the possible precursory group for centrarchidae could be. I find this particularly puzzling because sunfish are limited to north america. Unlike other groups of fish (sticklebacks, minnows, perches, pikes, catfish, sturgeon, paddlefish, etc.) that are currently found throughout the northern hemisphere and some (such as catfish) throughout the world. Even gar (currently limited to the new world) show up elsewhere in the world in the fossil record if what I read was right.

Does this imply sunfish were a more recently evolved group than other fish and haven't had the chance to spread that other groups have had? How come a more widespread group such as the perches didn't fill the evolutionary gap before they had a chance? If they were more recent where did they come from? If they were not more a recently evolved group what prevented their spread?

I know studies have been done showing the genetic relationships among different centrarchids. But have any studies been done comparing centrarchids to other perciformes?

Yes, although a new more thorough study is in the works right now. Basically centrarchids are most closely related to Elassoma. It is an interesting question as to why they are limited to North America (given that they are not a young group of fish) when the other groups are not, but, most of those other groups you listed are quite temperate and the east-west connections have all been the most suitable for species that live at higher northern latitudes.

Perches, as in the bigger species all mostly occur in northern portions of North America, whereas centrarchids have their highest diversity in the SE USA. How would a fish found in the SE USA get to another continent? The southern route is only relatively recent, plus they don't get anywhere close to central America. Also, there are lots of cichlids down there too that are likely strong competitors with fish like a sunfish. Anyway, if you go back a really really long way then there are connections to other continents, but that was involving the ancestor to the family, well before the sunfishes of today specifically evolved.

Cheers
Peter

My gut level guess on the limit of southern distribution also blames cichlids. As of 1979 Dr. Loiselle mentioned that the black acara (Cichlasoma Bimaculatum) and Tilapia Mariae Were the dominant mediu mand large Percoid fish in Florida waters. This is after a rather recent accidental introduction of cichlids. My guess is that the biparental mode of fry defense (as well as mouthbrooding in some Tilapia, although very few CA ciclids mouthbrood - you find more in SA), has a lot to do with the ability of cichlids to outcompete sunfish when the two are in the same waters. Being ecological analouges, Cichlids fill every niche that sunfish do, and then some.

That said, in waters devoid of cichlids introduced sunfish do rather well, and even manage to get a foothold in some waters with cichlids (although this is usually a black bass thing).