Reconsidering the Specialist-Generalist Paradigm in Niche Breadth Dynamics: Resource Gradient Selection by Canada Lynx and Bobcat

Abstract

The long-standing view in ecology is that disparity in overall resource selection is the basis for identifying niche breadth patterns, with species having narrow selection being classified “specialists” and those with broader selection being “generalists”. The standard model of niche breadth characterizes generalists and specialists as having comparable levels of overall total resource exploitation, with specialists exploiting resources at a higher level of performance over a narrower range of conditions. This view has gone largely unchallenged. An alternate model predicts total resource use being lower for the specialized species with both peaking at a comparable level of performance over a particular resource gradient. To reconcile the niche breadth paradigm we contrasted both models by developing range-wide species distribution models for Canada lynx, Lynx canadensis, and bobcat, Lynx rufus. Using a suite of environmental factors to define each species’ niche, we determined that Canada lynx demonstrated higher total performance over a restricted set of variables, specifically those related to snow and altitude, while bobcat had higher total performance across most variables. Unlike predictions generated by the standard model, bobcat level of exploitation was not compromised by the trade-off with peak performance, and Canada lynx were not restricted to exploiting a narrower range of conditions. Instead, the emergent pattern was that specialist species have a higher total resource utilization and peak performance value within a smaller number of resources or environmental axes than generalists. Our results also indicate that relative differences in niche breadth are strongly dependent on the variable under consideration, implying that the appropriate model describing niche breadth dynamics between specialists and generalists may be more complex than either the traditional heuristic or our modified version. Our results demonstrate a need to re-evaluate traditional, but largely untested, assumptions regarding resource utilization in species with broad and narrow niches.

Evidence for large-scale effects of competition: niche displacement in Canada lynx and bobcat

“…lower temperatures, higher snow cover and snow depth), which is better suited to lynx presence [27]. It follows that exploitative and/or interference competition probably limits lynx survival or productivity in the warmer, low-elevation extremes of their tolerability.…”

Occurrence patterns and niche relationships of sympatric owls in South American temperate forests: A multi-scale approach

“…occurrence, density) than generalists under a subset of relatively stable resources (Fig. 1b and c;Devictor et al, 2010;Peers et al, 2012). Narrower niches render specialists more prone to be negatively affected by habitat degradation and fragmentation, than generalists (Clavel et al, 2011).…”

Spatiotemporal variations in aphid‐parasitoid relative abundance patterns and food webs in agricultural ecosystems

“…Presumably, a high variance in the availability and the quality of host resources would be favorable for parasitoids presenting a generalist strategy. Similarly, a prevalence of specialist behavior could be expected in a stable environment (Peers et al 2012). Furthermore, a decrease in preferred resources could lead to an expansion of niche breadth, as individuals tend to accept previously unutilized resources (Araujo et al 2011).…”