Ecological outcomes of hybridization vary extensively in Catostomus fishes

Hybridization outcomes vary geographically and can depend on the
environment. Hybridization can also reshape biotic interactions, leading
to ecological shifts. If hybrids function differently ecologically in ways
that enhance or reduce fitness, and those ecological roles vary
geographically, ecological factors might explain variation in
hybridization outcomes. However, relatively few studies have focused on
ecological traits of hybrids. We compared the feeding ecology of
Catostomus fish species and hybrids by using stable isotopes δ13C and δ15N
as a proxy for diet and habitat use, and compared two native species, an
introduced species, and three interspecific hybrid crosses. We included
hybrids and parental species from seven rivers where hybridization
outcomes vary. Relative isotopic niches of native species varied
geographically, but native species did not fully overlap in isotopic space
in any river sampled, suggesting little overlap of resource use between
historically sympatric species. The introduced species overlapped with one
or both native species in every river, suggesting similar resource use and
potential competition. Hybrids occupied intermediate, matching, or more
transgressive isotopic niches, and varied within and among rivers.
Ecological outcomes of hybridization varied across locations, implying
that hybridization might have unpredictable, idiosyncratic ecological
effects. --