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The complexity of an ecological community can be distilled into a network, where diverse interactions connect species in a web of dependencies. Species interact directly with each other and indirectly through environmental effects, however to our knowledge the role of these ecosystem engineers has not been considered in ecological network models. Here we explore the dynamics of ecosystem assembly, where species colonization and extinction depends on the constraints imposed by trophic, service, and engineering dependencies. We show that our assembly model reproduces many key features of ecological systems, such as the role of generalists during assembly, realistic maximum trophic levels, and increased nestedness with mutualistic interactions. We find that ecosystem engineering has large and nonlinear effects on extinction rates. While small numbers of engineers reduce stability by increasing primary extinctions, larger numbers of engineers increase stability by reducing primary extinctions and extinction cascade magnitude. Our results suggest that ecological engineers may enhance community diversity while increasing persistence by facilitating colonization and limiting competitive exclusion.

"When animals die, waves of microbes consume their corpses. Scientists have looked at how this "necrobiome" changes over the hours and days after an animal perishes. But Saitta's work suggests that microbes continue to colonize cadavers long after their flesh has decayed, after their bones have turned to stone, and after they've been buried several miles deep for millions of years.   MORE STORIES A Dinosaur So Well Preserved, It Looks Like a Statue ED YONG How a Fossil Can Reveal the Color of a Dinosaur CARI ROMM The Counterintuitive Way That Microbes Survive in Antarctica ED YONG The Scientist Who Stumbled Upon a Tick Full of 20-Million-Year-Old Blood SARAH ZHANG That came as a huge surprise to Tullis Onstott, a microbiologist from Princeton who worked with Saitta, and who always thought of fossils as inert and inanimate. "I thought that dinosaur bone must be some kind of sealed sarcophagus," he says. "It's not, by any means. It's basically a condo for bacteria. Now the question becomes: Is this true for all dinosaur bones?""