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Re: nest predation

>> This means that one cannot actually
>> optimize nest parasitism on a tree such that nonavian theropods would be
>> predicted to show nest parasitism.  Still, it could happen.
>I would argue the opposite.  Nest parasitism--trusting your eggs to other
>parents--would be expected to be more common among taxa which practice
>active parental investment in the raising of their offspring.  Is that
>non-avian dinosaurs?  At least some, if not most, if not all, right?

Living crocs take active care of their young and do not parasitize nests,
but that's another matter.

Actually, you've missed my point entirely.  I was speaking of phylogenetic
optimization.  An example:

Living birds care for their nests.  So do crocodylians.  Most lepidosaurs
do not, and based on cladograms for that group nest defense is not
ancestral for Lepidosauria; turtles also do not care for their nests.  If
we map "nest defense" on a cladogram for living and extinct reptiles, we
would find nonavian dinosaurs falling out within a group that can be
bracketed as having nest defense, and we would predict nest defense in
them.  This has been called the "extant phylogenetic bracket," although
it's just DELTRANS optimization as one would normally use in PAUP.

How about something like Euparkeria, or an erythrosuchid? These are
archosauriforms, but not within the crown group.  We can optimize the
ancestral archosaur sensu stricto as having nest defense, but given that
the next living group out (Lepidosauria) does not ancestrally show nest
defense, we cannot say, on phylogenetic grounds, whether or not Euparkeria
showed nest defense.

How about something like Areoscelis?  All living groups near that taxon do
not defend nests, and so we would predict absence of that behavior.


Christopher Brochu

Postdoctoral Research Scientist
Department of Geology
Field Museum of Natural History
Lake Shore Drive at Roosevelt Road
Chicago, IL  60605  USA

phone:  312-922-9410, ext. 469
fax:  312-922-9566