LAUSR

Significance This work contains two major theoretical contributions: Firstly, we define a general set of measures, referred to as interconnectedness, which generalizes and combines classical notions of diversity and modularity. Secondly, we analyze the temporal evolution of interconnectedness based on a microscale model of ecoevolutionary dynamics. This we do by providing a platform for understanding how and why macroecological phenomena change over long time scales. Such a platform allows us to show how the drivers of the dynamics of macroecological descriptors, such as interconnectedness, can be partitioned into three components: (i) ecologically driven change, (ii) evolutionarily driven change, and (iii) environmentally driven change. In this contribution, we develop a theoretical framework for linking microprocesses (i.e., population dynamics and evolution through natural selection) with macrophenomena (such as interconnectedness and modularity within an ecological system). This is achieved by developing a measure of interconnectedness for population distributions defined on a trait space (generalizing the notion of modularity on graphs), in combination with an evolution equation for the population distribution. With this contribution, we provide a platform for understanding under what environmental, ecological, and evolutionary conditions ecosystems evolve toward being more or less modular. A major contribution of this work is that we are able to decompose the overall driver of changes at the macro level (such as interconnectedness) into three components: (i) ecologically driven change, (ii) evolutionarily driven change, and (iii) environmentally driven change.