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Re: flying Archie
The genome of the ancestral bird, _as it exists today_, outranks the
croc's by measures such as morphological/behavioral
complexity/diversity, and (I posit) the potential for the generation
of new forms to exploit both new and old environments. Ignoring the
fact that the final croc and the final bird are likely to die at the
same time (geologically speaking), is the croc more successful that
the bird? And if the timespan between the "first" and "final" croc is
larger than between "first" and "final" bird, does that mean the crocs
Great questions (and a good hypothetical). I would not call either
objectively more successful. I know that seems like a bit of a cop
out, but I do not see a way of making that comparison. The best that
can be done in that case is to compare different metrics at face value.
I do not see that scenario as one in which a "winner" can be declared,
unless the question is specified (such as: which group has been more
successful with regards to generating species diversity? Which clade
has traits that reduce extinction rates and promote species longevity?
I should also note that my original comments specifically referred to
species diversity alone. Character diversity is technically a separate
issue, and high character diversity probably reduces extinction and
promotes overall range size, etc. Of course, clades that are rich in
species are usually rich in characters as well (this includes
passerines), but that is not always the case. Mechanistically, both
forms of diversity need to be considered together, but they are
conceptually distinct with regards to judgements of "success".
Or, within birds, is the ancestral osprey (old species) more
successful than it's "clutchmate", that eventually gave rise to the
cardinal (young species), among many, many others?
Again, a good question. By one metric the osprey ancestor is more
successful, by another that honor goes to the cardinal ancestor. It
depends quite a bit on what sort of ecological mechanisms and
evolutionary patters you are interested in. For example, someone that
studies speciation will probably want to consider divergence rates and
clade size. Another worker that is more interested in extinction rates
might find species longevity more informative (though clade size still
matters because some groups are large by virtue of age, rather than
speciation rate). Still other workers might want to focus on biomass.
There are over 8 million chinstrap penguins, but there are only a small
number of penguin species. Are penguins successful? The answer
probably depends on what you work on.
Good discussion questions. I will have to think some more on how best
to approach such comparisons.