Data from: Introduced beaver improve growth of non–native trout in Tierra del Fuego, South America

Species introductions threaten ecosystem function worldwide and
interactions among introduced species may amplify their impacts. Effects
of multiple invasions are still poorly studied and often the mechanisms
underlying potential interactions among invaders are unknown. Despite
being a remote and well–conserved area, the southern portion of South
America has been greatly impacted by invasions of both the American Beaver
(Castor canadensis) and Brown Trout (Salmo trutta fario). Here, we
compared growth, condition, diet, and stable isotopes of sulfur δ34S,
nitrogen δ15N, and carbon δ13C for stream-living Brown Trout from streams
with (n = 6) and without (n = 6) beaver in Tierra del Fuego, Chile. We
show that beaver may facilitate the success of trout by positively
influencing fish growth. Beaver indirectly provide greater food subsidies
(i.e., macroinvertebrate abundances) by modifying the local aquatic
environment through active dam and lodge building suggesting a one–way
positive interaction. Trout in beaver-influenced streams occupied a
slightly higher trophic level with more depleted sulfur and carbon
isotopic ratios suggesting that food web pathways rely on secondary
production from autochthonous origin. Trout in beaver-influenced streams
have a wider dietary breadth with diptera and amphipoda as the prey items
providing most of the energy whereas in streams without beaver,
trichoptera were the main source of energy for trout. Although these two
invaders have never co-occurred naturally, their ecosystem function and
the beneficial influences of coexisting life histories reported in their
native ranges are similar to our findings from invaded systems.