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Understanding the past to preserve the future

Learn how comparisons of evolutionary relatedness can help us protect the greatest amount of biodiversity. Video by California Academy of Sciences.

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  • blobby green style avatar for user Cat lover
    I believe that organisms are able to cope with their falling numbers and regain those numbers if they are simply left alone in an undisturbed, intact, natural (endemic) habitat.
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Video transcript

(serene classical music) - [Narrator] We've mentioned this many times, saving biodiversity comes down to choices, hard choices about what biodiversity to save. Unfortunately, so much of the natural world is threatened by human activities, we have to make choices between what to prioritize for protection, we cannot save it all. There's ongoing discussion about what criteria and, most importantly, what tools we have at hand that we can and should use to help us make intelligent choices, choices that maximize ecosystem function, and along with that, ecosystem services. What do we actually focus on saving, a species, an ecosystem? A saved species isn't really saved if its ecosystem or habitat remains at risk. After all, you could lock all those endangered species safely in a zoo and keep their lineages going for quite a long time, but that doesn't really help the planet or us overall. What we're talking about is focusing on the preservation of functioning ecosystems. Most people would agree that we want to keep organisms in their native habitats, fulfilling functions so that the ecosystem sustains itself. A self-sustaining web of interactions in which species have connected but differing functions in that web. With limited resources such as time, money, and space available for protecting biodiversity, we're gonna have to decide if some ecosystems are more important to save than others. How do we choose? It's a nasty little question, but with the accelerating speed of this current sixth mass extinction, we really do need to address it quickly. One of the things that scientist have discovered is that in a healthy ecosystem, a diversity of things are going on among different species, and that leads to production of biomass. That's one measurement that scientists have been able to make. A healthy ecosystem tends to produce more biomass than a less healthy ecosystem. With more biomass, you have a more stable foundation to support more organisms within that ecosystem, and you're also sequestering more carbon that might otherwise add to climate change. So, higher biomass in an ecosystem is regarded as a good thing, at least in terms of a simple measure of ecosystem health. And as it turns out, recent carefully controlled experiments have shown that ecosystems made up of more distantly related species result in greater biomass. The reason for this is that distantly related organisms are more likely to fulfill functions in different, non-overlapping niches. In other words, they're not competing with closely related species that, because of their common ancestry, have similar tastes or needs for resources in the ecosystem. But how do you know that things are more or less distantly related? That's where phylogeny, the study of lineages, or evolutionary lineages, comes in. And I'm going to give you a little example that illustrates how this can be an important tool in our efforts to make decisions about where to focus our energies in saving ecosystems. Let's consider three lakes, Lake A, Lake B, and Lake C. And Lake A over here has a bunch of fish in it. Let's say there are four species, we're gonna call them A1, A2, A3, and A4. And then in Lake B, we've got four other species. And finally, in Lake C over here, we have yet another different set of four species of fish. Local governmental agencies want to preserve the healthiest ecosystem among these lakes, but due to the limited funding and staff they have to work with, they can only focus on saving one lake, that's the problem. If they only consider species richness, there's equal diversity. Four different fish species in each of these lakes. How do you decide which lake should receive your limited resources to preserve it? Well, we can do that by using phylogenetics. So we study all 12 of these fish species, and we build a phylogenetic tree using the latest and greatest of molecular and morphological methods. All these data help us to build a tree of life, this phylogeny. The first thing you can observe is that the four species in Lake A are more closely related to each other than they are to anything else. And the same is true for the four species in Lake B. But we've got one species from Lake C that's more closely related to those in Lake A, and another C species that's more closely related to the B species. And interestingly, the two remaining species from Lake C are closely related to each other, but form a group that is only distantly related to the species in either Lake A or Lake B. It's pretty obvious that the evolutionary distinctiveness, or diversity, among the four species from Lake C is much greater than the distinctiveness among the species in either Lake A or B. So if you wanna preserve really distinct species that most likely function in distinct niches that enhance biomass production and ecosystem health, our friendly government agencies should focus on efforts on protecting the Lake C ecosystem. Of course, real life is always more complicated than this simple example in which we've only varied the degree of evolutionary relatedness among species in each of the lakes. In real life, you have many factors that should be considered in decisions about what to protect, factors ranging from the total number of species in an ecosystem, to the value of the services provided by that ecosystem. But the point here is that we have a valid, powerful scientific tool, the study of phylogenetic lineages that can help us understand how different ecosystems possess different levels of productivity depending on the types of species they contain. As a scientist trying to deal with the enormity of the problems we face and the daunting task of trying to protect as many things as possible, I'm happy about new scientific tools that can help us make these most difficult choices. We need all the help we can get in trying to reduce the loss of biodiversity that we humans are causing because we are now arguably the most influential ever of all the species in the tree of life.