Emerging infectious diseases are triggered by a changing environment in many ecosystems and organisms, from humans to coral reefs [1].
Natural areas also provide many ecosystem services [10], [11].
This is a critical assumption (though admittedly a necessary simplification as we begin to address the problem) that is likely to be challenged for many ecosystems or for particular organisms as we measure and quantify interactions.
As these organisms became the dominant primary producers in many ecosystems, a series of trophic interactions (dotted lines) resulted in the loss of GULO in non-photosynthetic organisms, either by providing a ready supply of dietary ascorbate (resulting in ascorbate auxotrophy in heterotrophic organisms) or through putative horizontal gene transfer of GLDH (e.g., choanoflagellates).
Theoretically, anaerobic organisms are rich with selected species of microorganisms, which can be commonly found in many ecosystems, including lactic acid bacteria (LAB), yeasts, actinomycetes photosynthetic bacteria, and other types of organisms.
Lichens are symbiotic organisms consisting of algae and fungi, and are important constituents of many ecosystems.
Although some ecosystem responses to climate change are gradual, many ecosystems react in highly nonlinear ways.
In many ecosystems they are a major component of the arthropod fauna, and they are of high functional importance as predators and scavengers, as well as partners in several symbioses with other organisms [25], [26].
Our review emphasises that molecular nitrogen fixation, a driving force for interactions and co-evolution of different species, is a widespread phenomenon involving many different organisms and ecosystems.
A future challenge for ecological and evolutionary systems biology will be to apply the methods developed for model species to other species (Karrenberg and Widmer, 2008), in particular to keystone species, which affect many other organisms in an ecosystem.
