Would you save the young or the ancient species?

Yesterday I gave a seminar at John Harte's lab at UC Berkeley. It was a joy. There must be something in the lush Californian climate that makes people nice.

During the discussion John Harte and Andy Rominger jointly pointed me to a problem: Imagine that you have two species. The first one is a young species that originated recently. The second is a very old species. Now both of them are threatened by extinction, but you have resources to save only one of them. Which one would you choose to save?

I replied that it does not matter how old a species is. What matters is how many extant and close  relatives it has -- if the species has many relatives, you can sacrifice it because its evolutionary history will be preserved through the relatives. And then Andy brought up this killer dichotomy:

  • Yes, you may prefer to save the ancient species with few extant relatives (e.g. platypus) because it represents rare and 'evolutionarily distinct' lineage. If rarity and uniqueness is what you value, you save the ancient species.
  • But you may prefer the young species with many extant close relatives, for the whole clade has been diversifying rapidly.  Hence, each species in the clade has a potential to diversify further. In contrast, the ancient and lonely species apparently has not diversified. If diversity is what you value, you save the young species.

There may be a catch somewhere. I am not sure. Interestingly, the otherwise thorough review by Winter et al. (2012) in TREE does not mention this dichotomy. It mentions 'evolutionary potential' of a species, but only as a potential to adapt to environmental change, not as a potential to diversify.

I wonder if this problem is widely known in the conservation community, or whether there is some literature on it. Any ideas? And which species would you save?

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