Community-wide character displacement in the presence of clines: A test of Holarctic weasel guilds

Abstract

Summary 1.Competition is thought to be a major influence on community assembly, ecology and evolution; presence of competitors may cause divergence in traits related to resource use (character displacement). 2. Such traits, however, often vary clinally, and this phenomenon may be independent of the presence or absence of competing species. 3. The presence of such clines can either obscure the effects of competition, or create an impression that competition is operating when, in fact, it is not. 4. We corrected for clinal variation while testing for character displacement in two well-studied weasel (Mustela) guilds, in the Nearctic and the west Palaearctic. 5. Without accounting for clines, our results agreed with previous studies suggesting character displacement in these guilds. 6. However, when we corrected for clines, predictions of competition theory were not met -and often we obtained evidence for character convergence in sympatry. 7. This may suggest that the nature of the resource base may be more important than interspecific competition in shaping morphology and size in these carnivores. 8. Our results highlight the need to account for geographic variation when studying character displacement and cast some doubt on prevailing ideas regarding the effect of competition on morphological evolution.

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

“…To further address any possible unaccounted-for spatial factors influencing the comparison of niche similarity and breadth between lynx and bobcat, as well as to further account for potential clines or geographical variation that has affected previous displacement analysis [7,11], we followed the same procedure outlined above for comparing niche overlap and niche breadth, but with a comparably sized pseudo-intersect area for both species, which was located directly adjacent to the actual intersection zone (figure 1b). This was accomplished by buffering the intersect area to the north and south so that the size of the pseudo-intersect area for both species was equivalent to the real area of intersect.…”

“…The pseudo-intersect analysis ensures that the patterns seen are not the result of unaccounted-for geographical clines in species distributions, or vagaries of model-fitting and extrapolation (e.g. suspected displacement in weasel guilds was actually attributed to geographical clines in morphology rather than competitive influences [11]). Moreover, this test, as well as accounting for the available background through null models, allows us to rule out the potential confounding influence of differing ecological characteristics within the sympatric and allopatric zones on our analysis.…”

“…Therefore, a greater phenotypic difference between competitors should occur when species overlap in their distribution or space use [8]. It follows that such displacement may be a primary force in driving animal behaviour and evolution [10,11]. However, research in the area of ecological character displacement typically focuses on morphological traits (e.g.…”

Ecomorphology and foraging behaviour of Pacific boobies

“…in body mass; Dayan & Simberloff , Adams & Collyer , Meiri et al . ). Morphological dimorphism therefore could also be a consequence of ecogeographical adaptations to climate patterns or other environmental gradients (Gaston et al .…”

The role of character displacement in the molarization of hominin mandibular premolars

“…Although there are reservations regarding the strength of experimental evidence for character displacement (Grant ; Wiens ; Strong et al ; Slatkin ; Rundle et al ; Bo1nick and Fitzpatrick 2007; Meiri et al ; Stuart and Losos ), character displacement continues to be widely applied toward understanding morphological divergence in overlapping and potentially overlapping taxa (Schoener ; Taper and Case ; Abrams ; Schluter and McPhail ; Schluter ; Dayan and Simberloff ; Rando et al ). In its most straightforward form, character displacement can be quantified as the displacement statistic D S – D A , where D S denotes the divergence between sympatric (i.e., shared location) populations of two taxa and D A denotes the divergence between allopatric (i.e., different locations) populations of the same taxa (Schluter and McPhail ).…”