PageRank Algorithm Applied To the Food Web

An anonymous reader brings word of a new application for PageRank, Google's link analysis algorithm: monitoring the food web in an ecosystem. A team of researchers found that a modified version of PageRank can predict with great accuracy which species are vital to the existence of others. Quoting: "Every species is embedded in a complex network of relationships with others. A single extinction can cascade into the loss of seemingly unrelated species. Investigating when this might happen using more conventional methods is complicated, as even in simple ecosystems, the number of combinations exceeds the number of atoms in the universe. So, it would be impossible to try them all. Co-author Dr. Stefano Allesina realized he could apply PageRank to the problem when he stumbled across an article in a journal of applied mathematics describing the Google algorithm. 'First of all, we had to reverse the definition of the algorithm. In PageRank, a web page is important if important pages point to it. In our approach, a species is important if it points to important species.'"

Re:Why is this surprising?

[DeadDecoy]

Because it's a novel use of an existing method? It was published in PLoS and not some mathematics journal. So, while the algorithms are not new, they may be new to the intended audience. The actual claim of the article is that it can offer a predictive analysis of extinction rates of a species and validated them on some in-silico experiments. This could be useful for bench-scientists, as they could figure out what might happen in an experiment before running expensive tests. This might be useful for conservations trying to make sure whole ecosystems don't die out due to the removal of a species; the 'might' is significant as real-world ecosystems are generally more complex. But anyways, it's interesting because the models have practical application outside of theory to help us understand the world.

Re:Importance

[JorDan Clock]

The model helps determine if a species is important. That's the whole point. Previously, we didn't have an easy way to determine a particular species impact on an ecosystem until it was almost extinct or already gone. Now by using "PageRank" to determine their importance, we can model what will happen if specific species are no longer part of the food web.

Re:More than atoms in the universe?

[MyLongNickName]

Here ya go [wordpress.com]. About 59.

Re:More than atoms in the universe?

[MyLongNickName]

What does your tweezers and removing atoms have to do with combinations? It is trivial to come up with a situation where there are more possible combinations that atoms of the universe. The number of possible chess games starts to get close (magnitude of 50 versus 80 for the atoms in the universe. Slightly more complex scenarios would easily go past 10^80. The trick is to find a way to model the complexity with a much simpler algorithm.

Re:Importance

[Hadlock]

NO! Page Rank is not named after webPage. It's named after Larry Page who created it. Arrrgh.
 
http://en.wikipedia.org/wiki/PageRank
 
http://en.wikipedia.org/wiki/Larry_Page

Re:More than atoms in the universe?

[Anonymous Coward]

According to Wikipedia, [wikipedia.org] our best estimate of the number of atoms in the universe is 10^80. The smallest factorial greater than this number is 59! = 138 683 118 545 689 835 737 939 019 720 389 406 345 902 876 772 687 432 540 821 294 940 160 000 000 000 000 = 1.39 * 10^80. (The next smallest factorial is 58! = 2 350 561 331 282 878 571 829 474 910 515 074 683 828 862 318 181 142 924 420 699 914 240 000 000 000 000 = 2.35 * 10^78.)

Re:Why is this surprising?

[speedtux]

Mathematical biology has a history that goes back further than computer science. Many biologists probably know a lot more math and statistics than your average computer scientists.