Latitudinal variation in ecological opportunity and intraspecific competition indicates differences in niche variability and diet specialization of Arctic marine predators

摘要: Individual specialization (IS), where individuals within populations irrespective of age, sex, and body size are either specialized or generalized in terms resource use, has implications on ecological niches food web structure. Niche degree IS near-top trophic-level marine predators have been little studied polar regions with latitude. We quantified the large-scale latitudinal variation population- individual-level niche ringed seals (Pusa hispida) beluga whales (Delphinapterus leucas) using stable carbon nitrogen isotope analysis 379 paired seal liver muscle samples 124 skin from eight locations ranging low to high Arctic. characterized both within- between-individual predator at each location as well accounting for spatial differences isotopic ranges potential prey. Total width (TINW) decreased increasing Higher TINW values were associated greater opportunity (i.e., prey diversity) fish community which mainly consists Capelin (Mallotus villosus) Sand lance (Ammodytes sp.) lower latitudes Arctic cod (Boreogadus saida) latitudes. In beluga, their dietary consistency between tissues also known within-individual component (WIC) increased a near 1:1 ratio (slope = 0.84), suggesting generalization, whereas slope (0.18) WIC relative indicated individual higher TINWs. Our findings highlight level latitude likely response opportunity, species-specific plasticity resources environmental conditions rapidly changing ecosystem.