Problematic bird Orders

[Ken Kinman]

Dear All,
      I have been struggling with the various small Orders now included in clade Metaves.  I have concluded that Order Mesitornithiformes is probably closely related to Columbiformes (perhaps even more so than Pterocliformes or Opisthocomiformes).  And secondly, that Order Phaethontiformes (tropicbirds) are closely related to Apodiformes (swifts and hummingbirds).

     Unfortunately, Columbiformes and Apodiformes seem to have elevated base substitution rates in the molecular sequences I've looked at, and long branch divergence may make determining their close relatives very difficult using molecular data.  In any case, I am now leaning towards making tropicbirds a sister group to the Apodiformes (swifts and hummingbirds).  That big tropicbird bill doesn't look much like an apodiform bill, but if hummingbirds (with long bills) can evolved from swifts, then no reason tropicbirds couldn't have done the same thing (although for different reasons).  I'm not yet ready to place Phaethontidae within Order Apodiformes, but maybe eventually if more synapomorphies can be found to unite them.  Meanwhile, I really think I should at least treat them as sister groups.  Any comments?
   ----Cheers,
            Ken Kinman