Reduced intraspecific variation in lake trout food webs under warmer temperatures and smaller ecosystem sizes: data and code

Food web theory has illustrated that mobile top predators, such as lake
trout (Salvelinus namaycush), can be potent stabilizers of food webs due
to their ability to shift foraging behaviours in response to changing
conditions. Consistent with this, research has demonstrated that mean lake
trout food web attributes (i.e., trophic position and nearshore coupling)
structurally change across environmental gradients; however, intraspecific
variation in these attributes across gradients has not been fully
explored. Here, we used stable isotope-based food web metrics to
investigate how both mean and intraspecific variation in trophic structure
changes in Canadian boreal shield lakes across gradients in ecosystem
size, temperature and competition. Consistent with earlier findings, we
find nearshore coupling decreases and trophic position increases with
warmer summer climate. In contrast to previous findings, increasing lake
area predicted increased nearshore coupling and was not associated with
lake trout trophic position.  Our results show that warmer
temperatures and smaller ecosystem sizes reduce the expression of
intraspecific variation in food web structures. Specifically, larger lakes
increased variation in nearshore coupling and trophic position resulting
in larger niche areas, and warmer lakes reduced variation in nearshore
coupling and tended to generate smaller niche areas. Interestingly, we
found little evidence for the relative abundance of lake trout or other
predator taxa (surrogates of intra and interspecific competition)
influencing mean and variance in lake trout trophic structure.
Intraspecific variation can promote ecosystem resilience by enabling
diverse individual responses that help buffer populations against
environmental change. Therefore, reduction in intraspecific variation in
smaller, warmer lakes may have undesirable consequences for lake trout and
the biota in these Canadian boreal shield lakes, leaving these ecosystems
less able to adjust to future perturbations.