Changes in mean temperature can generate alternative
patterns of species coexistence
With the knowledge that combinations of different temporal scales of
environmental variation do not have a uniform or consistent effect on
species coexistence, the final question we ask is whether mean
temperature itself affects patterns of species coexistence (Fig. 4). The
previous coexistence-exclusion-coexistence result occurs at a mean
temperature (20 degrees) that lies in between the optimal temperatures
of the two competing species and allows coexistence in a stable
environment (Fig. 3a and 4g). However, if the mean temperature increases
(and becomes closer to the optimum of species 1), species coexistence
only occurs when variation is large (Fig. 4f). Furthermore, if the mean
temperature increases further, even greater environmental variation will
not generate species coexistence. In other words, when mean temperature
deviates from the intermediate temperature that is non-optimal for both
of the competing species and approaches the optimum of either species,
the relationship between environmental variation and species coexistence
may shift from coexistence-exclusion-coexistence (Fig. 4g-i) to one that
promotes coexistence (Fig. 4d-f) to one that favor coexistence but has
relatively weaker influence (Fig. 4a-c).