  Understanding the mechanisms of species coexistence has always been a
fundamental topic in ecology. Classical theory predicts that interspecific
competition may select for traits that stabilize niche differences, although
recent work shows that this is not strictly necessary. Here we ask whether
adaptive phenotypic plasticity could allow species coexistence (i.e., some
stability at an equilibrium point) without ecological differentiation in
habitat use. We used individual-based stochastic simulations defining a
landscape composed of spatially uncorrelated or autocorrelated environmental
patches, where two species with the same competitive strategies, not able to
coexist without some form of phenotypic plasticity, expanded their ranges in
the absence of a competition-colonization trade-off (a well-studied mechanism
for species diversity). Each patch is characterized by a random environmental
value that determines the optimal phenotype of its occupants. In such a
scenario, only local adaptation and gene flow (migration) may interact to
promote genetic variation and coexistence in the metapopulation. Results show
that a competitively inferior species with adaptive phenotypic plasticity can
coexist in a same patch with a competitively superior, non-plastic species,
provided the migration rates and variances of the patches' environmental values
are sufficiently large.
