The Loom of Life: Unravelling Ecosystems
En ze proberen een nest te maken op een plek waar ze wat hulp bij nodig hebben anders wordt t niks vrees ik. You are commenting using your WordPress. You are commenting using your Google account. You are commenting using your Twitter account.
You are commenting using your Facebook account. Notify me of new comments via email. Notify me of new posts via email. Share this: Twitter Facebook. Like this: Like Loading Leave a Reply Cancel reply Enter your comment here Fill in your details below or click an icon to log in:. One of the most important of those concepts was that plants and other photosynthetic organisms served as the foundation of life on Earth. These fundamental insights eventually led to important advances in conservation biology. They helped conservation biologists understand, for example, how pesticides and other pollutants ended up so concentrated in the bodies of large predators like polar bears and tuna.
Evolution and Ecology for Everyone
For decades, however, the best pictures of ecological networks remained extremely simple. Many ecologists also felt that it might not be worth fleshing out networks in too much detail. As networks became more focused and realistic, ecologists found that they became too complex to make sense of — let alone to yield any rules about ecological networks around the world. But ecologists have started to shed that pessimism in recent years. They have seen how scientists like Barabasi have been able to extract meaningful lessons from full-blown networks.
And so ecologists have borrowed these scientific methods to analyze networks without drowning in detail. Their studies have shed new light on the biggest debates in ecology. Most plants, for example, depend on animals of one sort or another to spread their pollen.
In some cases, scientists have discovered exquisitely co-evolved partners that specialize only on one another. For example, some flowers keep their nectar in deep recesses that can only be reached by flies with tongues stretching several inches in length. Ecologists have argued over which kind of partnership — specialized or generalized — is most important in ecosystems.
The answer has important practical significance. If many plant species each depend on just one pollinator, then they are exquisitely vulnerable to extinction if they lose their partner. Jordia Bascompte , an ecologist at the Spanish Research Council, and his colleagues have traveled to a number of ecosystems to catalog the plants animal pollinators visit and which animals visit each plant.
The picture is much the same from one ecosystem to another.
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Most animals and plants only form partnerships with a few other species. A few generalist animals and plants interact with many species. Generalists form a highly-linked core of the network, interacting with other generalists. The specialists tend to interact with these generalists rather than with each other, with the result that the pollinator network is arranged around hubs. In other words, a field of wildflowers is a lot like Hollywood.
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A generalist moth, for example, will visit several species of plants in search of food. In some ways, each species of plant might be better off if the moth only visited it and no other species. The moth would spread more of its pollen, and so more of the plants would be able to make seeds.
If the other species of plants visited by the moth can thrive, that means that the moths have nectar to eat. And that means they can make more moths—which in turn can make more visits to every individual plant species. By modeling these kinds of interactions, Bascompte has found that the small-world network of pollinators and plants fosters more biodiversity than other kinds of networks. This arrangement not only fosters more biodiversity, but also makes ecological networks better able to withstand assaults. Losing a single species is unlikely to bring ecosystems crashing down, because most species in an ecological network are only linked to a few other species.
As a result, its absence will have relatively small effect.glorcosrucar.tk
The Loom of Life: Unravelling Ecosystems
On the other hand, if a hub species becomes extinct, there may be big trouble. Recently, Bascompte and his colleagues drew the network of marine ecosystems in the Caribbean. They discovered that fish form interconnected clusters known as modules. In each module, the nodes are more connected to each other than to other nodes outside the module. Each module was organized around sharks, which acted as the top predators.
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Some modules contained a few species of sharks, but many included just one. The sharks may sort themselves into different modules as they avoid competing with one another for fish. The Caribbean network is thus organized around sharks, with each species a highly connected hub in its particular module. That arrangement means that overfishing sharks could have an even bigger effect on marine ecosystems than ecologists have previously realized.