Microbial communities feature an immense diversity of species and the extent of this diversity correlates with outcomes ranging from ecosystem stability to medical prognoses. Yet the mechanisms underlying microbial diversity are not well understood; simple resource-competition models do not allow for coexistence of a large number of species . However , it was recently shown that assuming the existence of metabolic trade-offs - in allocating a limited enzyme production capacity - can lead to unlimited diversity, when nutrients are steadily supplied. Do such trade-offs permit diversity under more realistic, intermittent conditions of nutrient supply? Here, we demonstrate  that in serial dilution culture, metabolic trade-offs allow for high diversity. Unlike the constant environment case , diversity depends on the concentration of nutrients supplied to the community. These changes in diversity are driven by an "early-bird" effect in which species specialized for nutrients that are initially more abundant gain a population advantage over other species. We explore the interplay of this effect with different environmental factors and diversity-supporting mechanisms , such as immigration and cross-feeding, and find a variety of ensuing relationships between nutrient supply and diversity . The large variation seen in this simple model suggests that real ecosystems may not obey a single universal relationship between nutrient supply and diversity. To connect to real microbial communities, we validate our growth model against previously published Escherichia coli batch and chemostat experiments and outline potential future experiments to test the model's multispecies predictions .
Microbial communities feature an immense diversity of species and this diversity is linked with outcomes ranging from ecosystem stability to medical prognoses. Yet the mechanisms underlying microbial diversity are under debate. While simple resource-competition models don't allow for coexistence of a large number of species , it was recently shown that metabolic trade-offs can allow unlimited diversity. Does this diversity persist with more realistic, intermittent nutrient supply? Here, we demonstrate theoretically that in serial dilution culture, metabolic trade-offs allow for high diversity. When a small amount of nutrient is supplied to each batch, the serial dilution dynamics mimic a chemostat-like steady state. If more nutrient is supplied , diversity depends on the amount of nutrient supplied due to an "early-bird" effect . The interplay of this effect with different environmental factors and diversity-supporting mechanisms leads to a variety of relationships between nutrient supply and diversity , suggesting that real ecosystems may not obey a universal nutrient-diversity relationship .
R
the extent of this diversity correlates
this diversity is linked
R
not well understood;
under debate. While
R
do not
don't
D
. However
D
assuming the existence of
R
- in allocating a limited enzyme production capacity - can lead to unlimited diversity, when nutrients are steadily supplied. Do such trade-offs permit diversity under
can allow unlimited diversity. Does this diversity persist with
D
conditions of
A
theoretically
R
Unlike the constant environment case
When a small amount of nutrient is supplied to each batch, the serial dilution dynamics mimic a chemostat-like steady state. If more nutrient is supplied
R
concentration of nutrients supplied to the community. These changes in diversity are driven by
amount of nutrient supplied due to
R
in which species specialized for nutrients that are initially more abundant gain a population advantage over other species. We explore the
. The
R
, such as immigration and cross-feeding, and find
leads to
D
ensuing
R
. The large variation seen in this simple model suggests
, suggesting
R
single universal relationship between nutrient supply and diversity. To connect to real microbial communities, we validate our growth model against previously published Escherichia coli batch and chemostat experiments and outline potential future experiments to test the model's multispecies predictions
universal nutrient-diversity relationship