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biological invasion; climate change; Coregonus lavaretus; Finnish Lapland; intraspecific morphs; lake depth; Perca fluviatilis; resource competition; species distribution; stable isotopes; thermal guild; trophic niche
Abstract:
Climate change is increasing ambient temperatures in Arctic and subarctic
regions, facilitating latitudinal range expansions of freshwater fishes adapted to warmer water
temperatures. The relative roles of resource availability and interspecific interactions between
resident and invading species in determining the outcomes of such expansions has not been
adequately evaluated.
Ecological interactions between a cool-water adapted fish, the perch (Perca fluviatilis), and
the cold-water adapted European whitefish (Coregonus lavaretus), were studied in both
shallow and deep lakes with fish communities dominated by (1) monomorphic whitefish, (2)
monomorphic whitefish and perch, and (3) polymorphic whitefish and perch. A combination
of stomach content, stable-isotope, and invertebrate prey availability data were used to
identify resource use and niche overlap among perch, the trophic generalist large sparsely
rakered (LSR) whitefish morph, and the pelagic specialist densely rakered (DR) whitefish
morph in 10 subarctic lakes at the contemporary distribution limit of perch in northern
Scandinavia.
Perch utilized its putative preferred littoral niche in all lakes. LSR whitefish utilized both
littoral and pelagic resources in monomorphic whitefish-dominated lakes. When found in
sympatry with perch, LSR whitefish exclusively utilized pelagic prey in deep lakes, but
displayed niche overlap with perch in shallow littoral lakes. DR whitefish was a specialist
zooplanktivore, relegating LSR whitefish from pelagic habitats, leading to an increase in niche
overlap between LSR whitefish and perch in deep lakes.
Our results highlight how resource availability (lake depth and fish community) governs
ecological interactions between native and invading species, leading to different outcomes even
at the same latitudes. These findings suggest that lake morphometry and fish community
structure data should be included in bioclimate envelope-based models of species distribution
shifts following predicted climate change.
