Re: Packing in the bats

[Michael Habib <mhabib5@jhmi.edu>]

> Possible reasons why flyers might have high species packing:  ability 
> to
> exploit steep or vertical surfaces; mobility - ability to use scattered
> resources.

Good call; those could definitely have an impact.

It is probably worth mentioning, however, that not all flyers tend 
towards high species packing.  Small-bodied, short-range taxa have a 
strong tendency to produce heterogenous, species-rich clades with high 
species packing.  Larger and/or wider ranging species produce the 
opposite, however.  Both "modes" persist over time, but probably for 
slightly different reasons: Long-distance flyers with wide geographic 
ranges are robust to local pertubations.  Many seabirds and raptors, as 
well as several pterosaur lineages, have both long durations in the 
fossil record, and I suspect that this is a result of have large 
ranges.  By contrast, species like passerines and vespertilionid bats 
probably have higher turnover rates, but they more than make up for it 
with a higher speciation rate.  In essence, at a higher clade level, 
both types of lineages persist for long periods of time, but the 
wide-rangers have a few morphs over a large area, while short-rangers 
are dominated by heterogenous distributions (many morphs, each with a 
small range, that altogether cover a wide area).

The difference in average home range, as well as emergent 
extinction/speciation rates probably have an impact on species packing. 
 That's my best hypothesis at the moment, in any case.

Cheers,

--Mike H.