Among-individual diet variation within a lake trout ecotype: lack of stability of niche use

Abstract

30Ecological opportunities present during colonization of novel environments can drive divergent 31 selection on traits, resulting in specialization of morphs to enhance efficient use of resources. 32Thus, in an ecologically polymorphic species, differences in resource specialization should be 33 found among morphs, and homogeneity in resource use expected within a morph. Using one of 34 four morphs in Great Bear Lake, we investigate whether specialization of trophic resources 35 among individuals occurs within this single morph, which could indicate a potential for 36 continued divergence. Four distinct dietary patterns of resource use within the lake trout morph 37 were detected from fatty acid composition. Feeding habits of different groups within the morph 38were not associated with detectable morphological or genetic differentiation, suggesting that 39 behavioral plasticity may have caused the trophic variation within this morph. A low level of 40 genetic differentiation was detected between exceptionally large-sized individuals and other 41 individuals. Investigating a geologically young system that displays high levels of intraspecific 42 diversity and focusing on dietary patterns of resource use variation of individuals suggested that 43 individual specialization can occur within a morph. 44 45

Dimensionality and modularity of adaptive variation: Divergence in threespine stickleback from diverse environments

“…Our findings suggest that divergence among populations is not typically constrained by the axis of greatest covariation, even within groups of traits that might be expected to respond to similar selection pressures. This conclusion is consistent with the known examples of highly divergent conspecific sympatric morphs even within a single habitat – especially among salmonids (Skúlason et al 1989; Jónsson 2000; Chaverie et al 2016; Muir et al 2016; Arostegui and Quinn 2019; Chaverie et al 2020), and is incompatible with a simple singly-peaked or – ridged fitness landscape. Although evidence from recent post-glacial radiations – like some sticklebacks and the Salvelinus species – are particularly compelling because of the relatively short period of time available for the reorientation of g max in a low-dimensional model of divergence, other radiations also provide support for multi-axis divergence that is inconsistent with low-dimensional adaptation constrained by genetic covariances (Velasco and Herrel 2007; Hulsey et al 2019; Levin et al 2021).…”