> Wouldn't that suggest that frugivorous megabats, with good eyesight > and no echolocation, evolved from insectivorous cave-dwelling > microbats with (presumably) small eyes and echolocatory abilities? > Surely that would require a lot of reversals in the megabats - > unless flapping flight evolved twice in bats.
The microbats are already paraphyletic with respect to the megabats. That hasn't been doubted for years: the molecular evidence is clear-cut, and the morphological evidence doesn't contradict it much. Plus, all known stem-bats all the way to *Onychonycteris* and probably beyond are microbats in terms of size and ecology.
Why couldn't the flightless stem-bats have been arboreal rather than cave-dwelling? Dropping is presumably similar in both cases.
I suppose the idea is that echolocation is necessary in caves but not an obvious idea elsewhere. The only echolocating birds spend a lot of time in caves.