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David W Pfennig - One of the best experts on this subject based on the ideXlab platform.
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Character Displacement and the origins of diversity.
The American naturalist, 2020Co-Authors: David W Pfennig, Karin S PfennigAbstract:In The Origin of Species, Darwin proposed his principle of divergence of Character (a process now termed "Character Displacement") to explain how new species arise and why they differ from each other phenotypically. Darwin maintained that the origin of species and the evolution of differences between them is ultimately caused by divergent selection acting to minimize competitive interactions between initially similar individuals, populations, and species. Here, we examine the empirical support for the various claims that constitute Darwin's principle, specifically that (1) competition promotes divergent trait evolution, (2) the strength of competitively mediated divergent selection increases with increasing phenotypic similarity between competitors, (3) divergence can occur within species, and (4) competitively mediated divergence can trigger speciation. We also explore aspects that Darwin failed to consider. In particular, we describe how (1) divergence can arise from selection acting to lessen reproductive interactions, (2) divergence is fueled by the intersection of Character Displacement and sexual selection, and (3) phenotypic plasticity may play a key role in promoting Character Displacement. Generally, Character Displacement is well supported empirically, and it remains a vital explanation for how new species arise and diversify.
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genetic accommodation in the wild evolution of gene expression plasticity during Character Displacement
Journal of Evolutionary Biology, 2017Co-Authors: Nicholas A Levis, Antonio Serratocapuchina, David W PfennigAbstract:Ecological Character Displacement is considered crucial in promoting diversification, yet relatively little is known of its underlying mechanisms. We examined whether evolutionary shifts in gene expression plasticity (‘genetic accommodation’) mediate Character Displacement in spadefoot toads. Where Spea bombifrons and S. multiplicata occur separately in allopatry (the ancestral condition), each produces alternative, diet-induced, larval ecomorphs: omnivores, which eat detritus, and carnivores, which specialize on shrimp. By contrast, where these two species occur together in sympatry (the derived condition), selection to minimize competition for detritus has caused S. bombifrons to become nearly fixed for producing only carnivores, suggesting that Character Displacement might have arisen through an extreme form of genetic accommodation (‘genetic assimilation’) in which plasticity is lost. Here, we asked if we could infer a signature of this process in regulatory changes of specific genes. In particular, we investigated whether genes that are normally expressed more highly in one morph (‘biased’ genes) have evolved reduced plasticity in expression levels among S. bombifrons from sympatry compared to S. bombifrons from allopatry. We reared individuals from sympatry vs. allopatry on detritus vs. shrimp and measured the reaction norms of nine biased genes. Although different genes displayed different patterns of gene regulatory evolution, the combined gene expression profiles revealed that sympatric individuals had indeed lost the diet-induced gene expression plasticity present in allopatric individuals. Our data therefore provide one of the few examples from natural populations in which genetic accommodation/assimilation can be traced to regulatory changes of specific genes. Such genetic accommodation might mediate Character Displacement in many systems. This article is protected by copyright. All rights reserved.
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development and evolution of Character Displacement
Annals of the New York Academy of Sciences, 2012Co-Authors: David W Pfennig, Karin S PfennigAbstract:Character Displacement occurs when competition for either resources or successful reproduction imposes divergent selection on interacting species, causing divergence in traits associated with resource use or reproduction. Here, we describe how Character Displacement can be mediated either by genetically canalized changes (i.e., changes that reflect allelic or genotype frequency changes) or by phenotypic plasticity. We also discuss how these two mechanisms influence the tempo of Character Displacement. Specifically, we suggest that, under some conditions, CharacterDisplacementmediatedbyphenotypicplasticitymightoccurmorerapidlythanthatmediatedbygenetically canalized changes. Finally, we describe how these two mechanisms may act together and determine Character Displacement’s mode, such that it proceeds through an initial phase in which trait divergence is environmentally induced to a later phase in which divergence becomes genetically canalized. This plasticity-first hypothesis predicts that Character Displacement should be generally mediated by ancestral plasticity and that it will arise similarly in multiple,independentlyevolvingpopulations.Weconcludebyhighlightingfuturedirectionsforresearchthatwould test these predictions.
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evaluating the targets of selection during Character Displacement
Evolution, 2011Co-Authors: Ryan Martin, David W PfennigAbstract:Ecological Character Displacement occurs when competition imposes divergent selection on interacting species, causing divergence in traits associated with resource use. Generally, divergence is assumed to occur when selection acts on the same, continuously varying trait in both species. However, selection might target multiple traits, and even closely related heterospecifics involved in Character Displacement might differ in selective targets. We investigated the targets of selection in a species of spadefoot toad, Spea multiplicata, during experimentally imposed competition with a congener, S. bombifrons. When examining traits separately, we found significant selection acting on multiple resource-acquisition traits. Yet, controlling for the independent effects of these traits in a multiple regression revealed that direct selection on a single trait might have contributed toward indirect selection on other correlated traits. Moreover, although we found evidence for plasticity in most traits, competition with S. bombifrons imposed selection on morphology and not on plasticity. Additional experiments suggest that the selective targets during Character Displacement might differ between the two species involved in this one instance of Character Displacement. Identifying the targets of competitively mediated selection is crucial, because whether and how Character Displacement ultimately unfolds depends on the nature of these targets and correlations among them.
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Character Displacement and the origins of diversity
The American Naturalist, 2010Co-Authors: David W Pfennig, Karin S PfennigAbstract:Abstract: In The Origin of Species, Darwin proposed his principle of divergence of Character (a process now termed “Character Displacement”) to explain how new species arise and why they differ from each other phenotypically. Darwin maintained that the origin of species and the evolution of differences between them is ultimately caused by divergent selection acting to minimize competitive interactions between initially similar individuals, populations, and species. Here, we examine the empirical support for the various claims that constitute Darwin’s principle, specifically that (1) competition promotes divergent trait evolution, (2) the strength of competitively mediated divergent selection increases with increasing phenotypic similarity between competitors, (3) divergence can occur within species, and (4) competitively mediated divergence can trigger speciation. We also explore aspects that Darwin failed to consider. In particular, we describe how (1) divergence can arise from selection acting to lessen...
Dean C. Adams - One of the best experts on this subject based on the ideXlab platform.
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Character Displacement VIA AGGRESSIVE INTERFERENCE IN
2020Co-Authors: Appalachian Salamanders, Dean C. AdamsAbstract:Ecological Character Displacement occurs when sympatric species compete with one another, resulting in morphological divergence. Theoretically, Character displace- ment can evolve from a number of ecological interactions, such as exploitation, interference, or predation, but most examples describe species competing exploitatively for limiting resources (typically food). Here I report a case of Character Displacement evolving from aggressive behavioral interference, found in a well-studied system of terrestrial salamanders of the genus Plethodon. Using geometric morphometrics, I found parallel shifts in head shape from allopatry to sympatry in both P. jordani and P. teyahalee, and found significantly greater morphological divergence in sympatry relative to allopatry. Both findings are con- sistent with ecological Character Displacement. I also show a significant association between morphology and aggressive behavior, demonstrating a direct link between interference competition and morphology. I present a modified set of the criteria for Character displace- ment that are appropriate for discriminating Character Displacement via aggressive inter- ference from other possible evolutionary mechanisms. For this example, empirical support satisfying five of the six criteria for Character Displacement is found. These results provide evidence that morphological variation can be generated by mechanisms other than resource exploitation, which has profound implications for interpreting patterns of biological di- versity.
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parallel evolution of Character Displacement driven by competitive selection in terrestrial salamanders
BMC Evolutionary Biology, 2010Co-Authors: Dean C. AdamsAbstract:Background: Parallel evolution can occur when common environmental factors exert similar selective forces on morphological variation in populations in different geographic localities. Competition can also generate morphological shifts, and if competing species co-occur in multiple geographic regions, then repeated instances of competitively-driven morphological divergence (Character Displacement) can occur. Despite the importance of Character Displacement for inferring the role of selection in morphological evolution however, replicated instances of sympatric morphological divergence are understudied. Results: I tested the hypothesis that interspecific competition generated patterns of parallel morphological divergence in multiple geographic locations where two competing salamander species, Plethodon jordani and P. teyahalee, come into contact. I used geometric morphometrics to Characterize head shape and found ecological Character Displacement in sympatric localities on each of three distinct mountains (geographic transects), where sympatric specimens displayed greater cranial differences and an increase in cranial robustness as compared to allopatric specimens. Using a recently developed analytical procedure, I also found that the observed morphological evolution within each species was consistent among transects; both in the total amount of morphological change as well as the direction of evolution in the morphological data space. This provided strong statistical evidence of parallel morphological evolution within species across replicate geographic transects. Conclusions: The results presented here reveal that the morphological evolution of each species followed a common evolutionary path in each transect. Because dispersal between sympatric locations among transects is unlikely, these findings suggest that the repeated instances of Character Displacement have evolved in situ. They also suggest that selection from competitive interactions plays an important role in initiating sympatric morphological divergence in these species, and drives parallel sympatric morphological divergence between species.
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Character Displacement via aggressive interference in appalachian salamanders
Ecology, 2004Co-Authors: Dean C. AdamsAbstract:Ecological Character Displacement occurs when sympatric species compete with one another, resulting in morphological divergence. Theoretically, Character displace- ment can evolve from a number of ecological interactions, such as exploitation, interference, or predation, but most examples describe species competing exploitatively for limiting resources (typically food). Here I report a case of Character Displacement evolving from aggressive behavioral interference, found in a well-studied system of terrestrial salamanders of the genus Plethodon. Using geometric morphometrics, I found parallel shifts in head shape from allopatry to sympatry in both P. jordani and P. teyahalee, and found significantly greater morphological divergence in sympatry relative to allopatry. Both findings are con- sistent with ecological Character Displacement. I also show a significant association between morphology and aggressive behavior, demonstrating a direct link between interference competition and morphology. I present a modified set of the criteria for Character displace- ment that are appropriate for discriminating Character Displacement via aggressive inter- ference from other possible evolutionary mechanisms. For this example, empirical support satisfying five of the six criteria for Character Displacement is found. These results provide evidence that morphological variation can be generated by mechanisms other than resource exploitation, which has profound implications for interpreting patterns of biological di- versity.
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Character Displacement and Aggression in Two Species ofTerrestrial Salamanders
Copeia, 2002Co-Authors: Robert G. Jaeger, Ethan D. Prosen, Dean C. AdamsAbstract:Abstract Two species of plethodontid salamanders (Plethodon cinereus and Plethodon hoffmani) exhibit Character Displacement with respect to body size and head morphology in Pennsylvania. In areas of allopatry, the two species do not differ in these traits while in an area of sympatry, P. cinereus is smaller (and eats smaller prey) and P. hoffmani is larger (and eats larger prey) in body size and head morphology. We tested the hypothesis that this form of Character Displacement is a consequence of alpha selection, in which natural selection favors increased aggression of sympatric species relative to their allopatric conspecifics. We found little evidence that allomonal response to or aggressive behavior toward heterospecifics differed significantly between allopatric and sympatric populations of either P. cinereus or P. hoffmani. Thus our data do not support the hypothesis of alpha selection shaping the morphology of the two species in sympatry. However, we found that both allopatric and sympatric populat...
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ecological Character Displacement in plethodon biomechanical differences found from a geometric morphometric study
Proceedings of the National Academy of Sciences of the United States of America, 2000Co-Authors: Dean C. Adams, James F RohlfAbstract:Ecological Character Displacement describes a pattern where morphological differences between sympatric species are enhanced through interspecific competition. Although widely considered a pervasive force in evolutionary ecology, few clear-cut examples have been documented. Here we report a case of ecological Character Displacement between two salamander species, Plethodon cinereus and Plethodon hoffmani. Morphology was quantified by using linear measurements and landmark-based geometric morphometric methods for specimens from allopatric and sympatric populations from two geographic transects in south-central Pennsylvania, and stomach contents were assayed to quantify food resource use. Morphological variation was also assessed in 13 additional allopatric populations. In both transects, we found significant morphological differentiation between sympatric populations that was associated with a reduction in prey consumption in sympatry and a segregation of prey according to prey size. No trophic morphological or resource use differences were found between allopatric populations, and comparisons of sympatric populations with randomly paired allopatric populations revealed that the observed sympatric morphological differentiation was greater than expected by chance. The major trophic anatomical differences between sympatric populations relates to functional and biomechanical differences in jaw closure: sympatric P. hoffmani have a faster closing jaw, whereas sympatric P. cinereus have a slower, stronger jaw. Because salamanders immobilize prey of different sizes in different ways, and because the observed sympatric biomechanical differences in jaw closure are associated with the differences in prey consumption, the observed Character Displacement has a functional ecological correlate, and we can link changes in form with changes in function in this apparent example of Character Displacement.
Alexander N G Kirschel - One of the best experts on this subject based on the ideXlab platform.
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range wide spatial mapping reveals convergent Character Displacement of bird song
Proceedings of The Royal Society B: Biological Sciences, 2019Co-Authors: Alexander N G Kirschel, Nathalie Seddon, Joseph A TobiasAbstract:A long-held view in evolutionary biology is that Character Displacement generates divergent phenotypes in closely related coexisting species to avoid the costs of hybridization or ecological compet...
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range wide spatial mapping reveals convergent Character Displacement of bird song
bioRxiv, 2019Co-Authors: Alexander N G Kirschel, Nathalie Seddon, Joseph A TobiasAbstract:Abstract A long-held view in evolutionary biology is that Character Displacement generates divergent phenotypes in closely related coexisting species to avoid the costs of hybridisation or ecological competition, whereas an alternative possibility is that signals of dominance or aggression may instead converge to facilitate coexistence among ecological competitors. Although this counter-intuitive process—termed convergent agonistic Character Displacement—is supported by recent theoretical and empirical studies, the extent to which it drives spatial patterns of trait evolution at continental scales remains unclear. By modeling variation in song structure of two ecologically similar species of Hypocnemis antbird across western Amazonia, we show that their territorial signals converge such that trait similarity peaks in the sympatric zone, where intense interspecific territoriality between these taxa has previously been demonstrated. We also use remote sensing data to show that signal convergence is not explained by environmental gradients and is thus unlikely to evolve by sensory drive (i.e. acoustic adaptation to the sound transmission properties of habitats). Our results suggest that agonistic Character Displacement driven by interspecific competition can generate spatial patterns opposite to those predicted by classic Character Displacement theory, and highlight the potential role of social selection in shaping geographical variation in signal phenotypes of ecological competitors.
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Character Displacement of song and morphology in african tinkerbirds
Proceedings of the National Academy of Sciences of the United States of America, 2009Co-Authors: Alexander N G Kirschel, Daniel T Blumstein, Thomas B SmithAbstract:Divergence in acoustic signals between populations of animals can lead to species recognition failure, reproductive isolation, and speciation. Character Displacement may facilitate coexistence of species in natural communities, yet evidence for Character Displacement in acoustic signals is scant. Here, we find evidence of Character Displacement in song as well as body size and bill size of 2 related African tinkerbirds. Playback experiments indicate that related species’ songs are perceived differently in sympatry than in allopatry. We suggest Character Displacement occurs in phenotypic traits facilitating species recognition, which has important implications for understanding the processes that lead to speciation and diversification. Because many of the sites where the 2 species coexist are areas where pristine rainforest has been degraded, results also suggest that anthropogenic pressures resulting from deforestation may be a contributing cause of Character Displacement in these species. animal communication environmental gradients interspecific competition species recognition phenotypic evolution
Joseph A Tobias - One of the best experts on this subject based on the ideXlab platform.
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range wide spatial mapping reveals convergent Character Displacement of bird song
Proceedings of The Royal Society B: Biological Sciences, 2019Co-Authors: Alexander N G Kirschel, Nathalie Seddon, Joseph A TobiasAbstract:A long-held view in evolutionary biology is that Character Displacement generates divergent phenotypes in closely related coexisting species to avoid the costs of hybridization or ecological compet...
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range wide spatial mapping reveals convergent Character Displacement of bird song
bioRxiv, 2019Co-Authors: Alexander N G Kirschel, Nathalie Seddon, Joseph A TobiasAbstract:Abstract A long-held view in evolutionary biology is that Character Displacement generates divergent phenotypes in closely related coexisting species to avoid the costs of hybridisation or ecological competition, whereas an alternative possibility is that signals of dominance or aggression may instead converge to facilitate coexistence among ecological competitors. Although this counter-intuitive process—termed convergent agonistic Character Displacement—is supported by recent theoretical and empirical studies, the extent to which it drives spatial patterns of trait evolution at continental scales remains unclear. By modeling variation in song structure of two ecologically similar species of Hypocnemis antbird across western Amazonia, we show that their territorial signals converge such that trait similarity peaks in the sympatric zone, where intense interspecific territoriality between these taxa has previously been demonstrated. We also use remote sensing data to show that signal convergence is not explained by environmental gradients and is thus unlikely to evolve by sensory drive (i.e. acoustic adaptation to the sound transmission properties of habitats). Our results suggest that agonistic Character Displacement driven by interspecific competition can generate spatial patterns opposite to those predicted by classic Character Displacement theory, and highlight the potential role of social selection in shaping geographical variation in signal phenotypes of ecological competitors.
Dolph Schluter - One of the best experts on this subject based on the ideXlab platform.
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moving Character Displacement beyond Characters using contemporary coexistence theory
Trends in Ecology and Evolution, 2017Co-Authors: Rachel M Germain, Dolph Schluter, Jennifer L Williams, Amy L AngertAbstract:Character Displacement is one of the most studied phenomena in evolutionary biology, yet research has narrowly focused on demonstrating whether or not Displacement has occurred. We propose a new experimental approach, adopted from the coexistence literature, that directly measures interspecific competition among sympatric and allopatric populations of species. Doing so allows increased ability to (i) test predictions of Character Displacement without biases inherent to Character-centric tests, (ii) quantify its effect on the stability of coexistence, (iii) resolve the phenotypic pathways through which competitive divergence is achieved, and (iv) perform comparative tests. Our approach extends research to forms of Character Displacement not readily identified by past methods and will lead to a broader understanding of its consequences for community structure.
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Character Displacement of male nuptial colour in threespine sticklebacks gasterosteus aculeatus
Biological Journal of The Linnean Society, 2007Co-Authors: Arianne Y K Albert, Nathan P Millar, Dolph SchluterAbstract:Character Displacement in signalling traits occurs when differences between species are greater in sympatry than where either species occurs alone. Finding Character Displacement in a signalling trait suggests that the trait has diverged as a result of interspecific interactions such as competition, aggression, predation, or reproductive interference. We tested for Character Displacement of male nuptial coloration between sympatric species of threespine sticklebacks (Gasterosteus aculeatus spp.). The sympatric pairs consist of a large ‘benthic’ species, which feeds on benthic invertebrates, and a smaller planktivorous ‘limnetic’ species. Breeding males of both species develop red throats and blue bodies, although limnetic males appear brighter. To test for Character Displacement, we compared the nuptial colour of benthics and limnetics from two species-pair lakes (sympatric) with that of males from three similar allopatric lakes (only one species present). We measured the intensity of blue and red coloration using reflectance spectra taken from live fish. We found that allopatric males were intermediate between limnetic and benthic males in the intensity of red colour, indicating Character Displacement in that trait in sympatry. By contrast, we found no evidence for Character Displacement in blue intensity, although it differed sharply between the species pairs in one lake (Priest). © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 91, 37–48.
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frequency dependent natural selection during Character Displacement in sticklebacks
Evolution, 2003Co-Authors: Dolph SchluterAbstract:We know little about how natural selection on a species is altered when a closely related species consuming similar resources appears in its environment. In a pond experiment with threespine sticklebacks I tested the prediction that divergent natural selection between competitors is frequency-dependent, changing with the distribution of phe- notypes in the environment. Differential growth and survival of phenotypes in a target stickleback population were contrasted between two treatments. In one treatment an offshore zooplankton feeder (the limnetic stickleback species) was added to the same pond as the target. In the other treatment I added the benthic stickleback instead, a species adapted to feeding on invertebrates from sediments and inshore vegetation. The target population was ecologically and morphologically intermediate with phenotypic variance artificially inflated by hybridization. Growth rates of phenotypes within the target population differed between treatments as predicted by Character Displacement. The impact of adding a second species always fell most heavily on those phenotypes in the target population resembling the added species most closely. However, those individuals in the target population that most resembled the added species did not experience reduced survival. Instead, consistent survival differences between populations suggested the presence of an inshore 2offshore gradient in mortality risk. These results provide further support for the hypothesis of Character Displacement in sympatric sticklebacks. They suggest that Displacement along the resource gradient also led to divergence in vulnerability to agents of mortality, probably including predation.
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ecological Character Displacement in adaptive radiation
The American Naturalist, 2000Co-Authors: Dolph SchluterAbstract:abstract: I give an overview of the observational and experimental evidence for ecological Character Displacement in adaptive radiation. Sixty‐one published cases of Character Displacement involving closely related species (congeners) make up the observational data set. All cases involve divergence, even though parallel and convergent Displacement are theoretically possible. Character ratios in sympatry were greatest when Displacement was symmetric (mean 1.54) and least when asymmetric (mean 1.29), perhaps because the most symmetric resource distributions are also the broadest. Carnivores are vastly overrepresented in the data compared with other trophic groups, with herbivores the next most common category. I consider five hypotheses to explain this pattern, including the possibility that the likelihood of divergence via competition depends on position in food webs. Overall, the quality and completeness of observational data has improved in recent years, as judged by the extent to which individual cases ...
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Character Displacement and replicate adaptive radiation
Trends in Ecology and Evolution, 1993Co-Authors: Dolph Schluter, J D McphailAbstract:Abstract Ecological Character Displacement is implicit in current views of adaptive radiation, but examples are few. The paucity of cases may be partly a problem of detection: statistical tests require that a consistent pattern of Displacement be observed over independent lineages, yet opportunities for such replication may be few. Recent studies of fish in postglacial lakes and lizards on Caribbean islands reveal multiple speciation events accompanied by equivalent patterns of ecological and morphological divergence. These studies provide a wealth of new examples of apparent Character Displacement, and show that adaptive radiations may unfold in a predictable sequence.