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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 have won?

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? etc.)

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.


--Mike Habib