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?

One thought on “Would you save the young or the ancient species?

  1. Ignacio Quintero replied in an e-mail:
    - I don't see any connection between a lineage that has been diversifying quickly and its potential to diversify further or vice versa. There are many examples of lineages that have not diversified for a long time that suddenly radiate because of a new opportunity. Also, species that come from a radiation burst might diversify more... or not.
    - I feel like it is more important to focus on why are you trying to conserve either ancient or young species. If you are worried on ecosystem services, for instance, it is more likely that young species are somewhat redundant while ancient ones are not; but again, not necessarily. You just measure their role. If you want relict genetic data, go for the ancient one, etc...
    The conservation debate is based on this later issue, what is the purpose of conserving. I personally feel that given our rate of degradation and non-conservations/biologist interests, we must focus on ecosystem services.

    Eric Waller wrote:
    I would just say that we shouldn't even be going down that road - diversity, per se, should probably not be our metric of interest, given that non-charismatic microfauna could diversify rapidly.

    Dan Rosauer wrote:
    This question has been much discussed. The concept of nursery v museum of biodiversity comes to mind. But I'm not aware of anything very definitive. It seems to appear in discussions, not results.
    But without answering the question, I would like to refine it a little.
    So if we have two families, one with 500 'young' species, the other with 1 species lacking close relatives. Now we might well decide that the diversifying family is more important for the future of biodiversity. But that is not the question here.
    The question is about one species. If we ensured the persistence of one threatened species in that clade of 500, how much might that contribute to future diversity of species, or to future PD?
    Would that species alone (forgetting its many near relatives) be more likely to sire a long-lived lineage, than it's lonely counterpart in the monospecific family? One could shed some light on this with simulations of diversification.
    And if that species were lost, how likely would it be that a related species would adapt / diversify to again fill that geographic / ecological / functional niche? In other words, are some steps in evolution more repeatable than others because closely related forms, the raw materials, are still available?
    So if one concludes that diversity will likely be greater in the longer term because of that species one 'young' species then there is a good argument for protecting it over the old species.
    The Davies et al (2011) Plos Biology paper showing that young species (of South African plants) are more likely to be threatened, is worth mentioning. Easy come easy go...

    Marten Winter wrote:
    I think this is still part of the „evolutionary potential“ discussion.
    Why should we care about speciation? Why are new species may be of interest, beside being totally new biological entities? I think because part of it might lead to species which are better adapted to new/changing environments.
    In any case. Where is any evidence for that  ?
    I’d love see more studies here...I think there was this special issue dealing with evolutionary rescue which goes into that direction: http://rstb.royalsocietypublishing.org/site/2013/rescue.xhtml

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