In addition to dynamics at layered levels of organization, the propensity of entities to alter (i.e. evolve) parameter values is the most unique, and challenging aspect of research in any area of biology. Evolutionary biologists are realizing the need for integrating the environmental contribution to phenotypic evolution. Concomitantly, anthropogenic alterations to global biogeochemistry have aided ecologists in recognizing that evolutionary change can occur rapidly, and that such evolutionary shifts are ecologically relevant. Environmental change at the ecosystem level is often characterized by (or strongly correlated to) alterations in the supply of the 25 elements involved in biology. The supply of these elements represent a precisely quantifiable environment on which phenotypic evolution happens. The acquisition and assimilation of elements from the environment, and allocation of elements within the body represent genomic capabilities of individuals that determine their elemental content, while the unused elements are released back into the environment, representing a fundamental ecological function. Together, these traits are referred to as the elemental phenotype (i.e. the elemental content and processing of the 25 elements required for life). 

Left: Schematic representation of the mass-balance-based elemental framework proposed for a single element and a single genotype. Based on first principles, the concentration of an element in an individual is a function of acquisition, assimilation, and allocation of the element. The excretion (i.e. unused or waste) of this element can be predicted applying mass balance. Note that this framework applies to all of the ~25 elements represented in biology (Right; grey squares).
Such a synthesis of ecology and evolution at the elemental level raises several key questions: (i) does the environmental supply of elements drive evolutionary shifts in elemental content and use? (ii) what are the evolutionary mechanisms that drive such shifts? And, (iii) are evolutionary shifts in elemental content and use ecologically relevant? 

We are currently addressing such questions in two systems, Daphnia, and Hyalella. Our specific interests in these two model organisms is because: (i) our lab is set up for quantitative genetic, and mesocosm studies on aquatic crustaceans, and (ii) studying these two taxa allows us to test the aforementioned questions in light of natural (Daphnia) and sexual (Hyalella) selection. In addition, several collaborative studies are underway on: Amazon mollies, fruit flies, stickleback, and zebra mussels to test similar questions. 

While much work remains, it is evident that an elemental approach is bound to reveal fundamental rules the underlie the dynamic interactions between ecology and evolution. For example, it is evident that of the 25 elements in biology, genetic variation in the content of some elements in individuals is higher, and less plastic compared to others. This indicates that some elemental traits may be more sensitive to environmental change compared to others. Whether the genomic regions associated with such traits are also more sensitive to environmental change remains an important question in genomics, evolution, as well as ecology. Importantly, because biogeochemical cycles are fundamentally linked, altering one or a few (e.g., C, P), can trigger rapid shifts in the supplies of other elements. Such information should help in the formulation of models that describe eco-evolutionary dynamics for a predictive understanding of not only the evolutionary consequences of global change, but also the associated shifts in the ecological functions of evolving populations.

Admittedly, it is a rather simple model to explore the mechanistic links between ecology and evolution. Nevertheless, we do not have a formal theory that describes the dynamic links between ecology and evolution that can be empirically verified in the wild without any taxa- or system-specific biases. Developing a logically consistent, and empirically verifiable model, that is generally relevant is a central frontier. There is nothing more fundamental than elements that link ecology and evolution, as Lotka notes above. Theoretical developments in both ecology and evolution, and technological advances in reliably and rapidly quantifying the entire suite of elements at multiple levels of biological organization enables us to rigorously test Lotka’s poetic musing from almost a century ago.
“For the drama of life is like a puppet show in which stage, scenery, actors and all are made of the same the stage and players are bound catch the spirit of the piece, our attention must not all be absorbed in the players alone, but must extend also to the stage, of which they are born, on which they play their part, and with which, in a short while, they merge again.” 
                                                                                                                                         - Alfred J. Lotka (1925).