Although the use of distinct colors to indicate unprofitability to predators(i.e.aposematism)is commonly thought of as an adaptation,our knowledge of its macroevolutionary effects is limited.Because aposematism is exp...Although the use of distinct colors to indicate unprofitability to predators(i.e.aposematism)is commonly thought of as an adaptation,our knowledge of its macroevolutionary effects is limited.Because aposematism is expected to decrease attacks by predators,we hypothesized that aposematic lineages should be larger on average than their non-aposematic sister groups because of the decreased probability of extinction and/or increased probability of speciation(i.e.increased diversification).The results of our sister-group analysis are consistent with the hypothesis that the evolution of aposematism is accompanied by increased diversification of lineages,with the aposematic focal group having more species in 11 of 14 pairs of sister groups.Despite the apparent advantages of reduced predation risk on diversification rates,the evolution of aposematism is relatively rare and reversions to a cryptic state are not uncommon.In addition to the difficulties in evolving a trait that initially decreases the survivorship of prey among naïve predators,we discuss other factors that may limit the apparent prevalence and success of aposematism.It is hoped that the results of our analysis will encourage further analyses of the phylogenetic relationships among aposematic groups and their relatives,and of the evolutionary time scales over which the benefits of aposematism are the greatest to lineages with this condition.展开更多
A laboratory colony of Coleomegilla maculata (De Geer) was selected for a novel phenotypic color trait. The phenotype was paler in color than the wild type, although not as pale as a previously described mutant strain...A laboratory colony of Coleomegilla maculata (De Geer) was selected for a novel phenotypic color trait. The phenotype was paler in color than the wild type, although not as pale as a previously described mutant strain, yellow (ye), and retained dark pigmentation in the eyes. This selected strain was named gold. Mendelian breeding experiments indicate a recessive biallelic inheritance. The strain has decreased fitness characteristics based on measurements of egg production and pupa size.展开更多
Color polymorphisms have been traditionally attributed to apostatic selection.The perception of color depends on the visual system of the observer.Theoretical models predict that differently perceived degrees of consp...Color polymorphisms have been traditionally attributed to apostatic selection.The perception of color depends on the visual system of the observer.Theoretical models predict that differently perceived degrees of conspicuousness by two predator and prey species may cause the evolution of polymorphisms in the presence of anti-apostatic and apostatic selection.The spider Gasteracantha cancriformis(Araneidae)possesses several conspicuous color morphs.In orb-web spiders,the prey attraction hypothesis states that conspicuous colors are prey lures that increase spider foraging success via flower mimicry.Therefore,polymorphism could be maintained if each morph attracted a different prey species(multiple prey hypothesis)and each spider mimicked a different flower color(flower mimicry hypothesis).Conspicuous colors could be a warning signal to predators because of the spider's hard abdomen and spines.Multiple predators could perceive morphs differently and exert different degrees of selective pressures(multiple predator hypothesis).We explored these 3 hypotheses using reflectance data and color vision modeling to estimate the chromatic and achromatic contrast of G.cancriformis morphs as perceived by several potential prey and predator taxa.Our results revealed that individual taxa perceive the conspicuousness of morphs differently.Therefore,the multiple prey hypothesis and,in part,the multiple predator hypothesis may explain the evolution of color polymorphism in G.cancriformis,even in the presence of anti-apostatic selection.The flower mimicry hypothesis received support by color metrics,but not by color vision models.Other parameters not evaluated by color vision models could also affect the perception of morphs and influence morph survival and polymorphism stability.展开更多
Chemical defenses are frequently accompanied by salient color patterns actively avoided by predators,a phe-nomenon referred to as aposematism.However,the production of both chemical defenses and pigments is costly,and...Chemical defenses are frequently accompanied by salient color patterns actively avoided by predators,a phe-nomenon referred to as aposematism.However,the production of both chemical defenses and pigments is costly,and is thus expected to be reduced under mild predator pressure.In this work,I compared the size and coloration of parotoid glands(2 dorsal,external swollen structures that secrete toxins in toads)of male and female Epidalea calamita toads from agrosystems and from pine groves.I also quantified the predator attacks received by plas-ticine toad models,whose“parotoid glands”differed in size and color conspicuousness,exposed in each habitat.Predators avoided models with large and conspicuous parotoid glands,but models in agrosystems were more of-ten attacked.Concerning actual toads,agrosystem and male individuals had larger parotoid glands,presumably implying greater production of chemical defenses than in pine grove and female conspecifics.Thesefindings are aligned with previous research suggesting that both agrosystem toads and males in this system are subjected to a more intense predator pressure.Difference between parotoid gland and dorsum coloration was greater in agrosys-tem toads.A marked internal pattern could function as an aposematic signal,which could counteract increased predator pressure.展开更多
Batesian mimicry is the process in which harmless species adopt the appearance of a dangerous, aposematic species.In some prey species,both Batesian mimetic and non-Batesian morphs coexist,presupposing that both morph...Batesian mimicry is the process in which harmless species adopt the appearance of a dangerous, aposematic species.In some prey species,both Batesian mimetic and non-Batesian morphs coexist,presupposing that both morphs have to be evolutionarily advantageous.The viperine snake, Natrix maura,exhibits a zigzag dorsal pattern and antipredatory behavior that mimics European vipers.This snake also has a striped dorsal pattern that coexists with the zigzag pattern.We have examined whether individuals belonging to different geographically structured clades were more likely to exhibit a certain dorsal pattern,and whether the zigzag pattern has a protective function by exposing artificial snakes to predation in natural environments,in addition to comparing antipredatory behavior between zigzag and striped snakes also in natural environments.Our results indicate that the striped pattern was not geographically structured,but habitat-dependent.Aerial predators less frequently attacked zigzag plasticine models than striped or unpatterned models.We detected a shift in antipredator behavior between the 2 morphs,as Batesian mimicking N.maura responded to an approaching potential predator by remaining immobile or fleeing at shorter distances than did striped ones.We conclude that Batesian mimics maintain the cryptic and aposematic value by resembling vipers,whereas in open habitats the non-Batesian mimic has altered its antipredator behavior to maintain its fitness.展开更多
文摘Although the use of distinct colors to indicate unprofitability to predators(i.e.aposematism)is commonly thought of as an adaptation,our knowledge of its macroevolutionary effects is limited.Because aposematism is expected to decrease attacks by predators,we hypothesized that aposematic lineages should be larger on average than their non-aposematic sister groups because of the decreased probability of extinction and/or increased probability of speciation(i.e.increased diversification).The results of our sister-group analysis are consistent with the hypothesis that the evolution of aposematism is accompanied by increased diversification of lineages,with the aposematic focal group having more species in 11 of 14 pairs of sister groups.Despite the apparent advantages of reduced predation risk on diversification rates,the evolution of aposematism is relatively rare and reversions to a cryptic state are not uncommon.In addition to the difficulties in evolving a trait that initially decreases the survivorship of prey among naïve predators,we discuss other factors that may limit the apparent prevalence and success of aposematism.It is hoped that the results of our analysis will encourage further analyses of the phylogenetic relationships among aposematic groups and their relatives,and of the evolutionary time scales over which the benefits of aposematism are the greatest to lineages with this condition.
文摘A laboratory colony of Coleomegilla maculata (De Geer) was selected for a novel phenotypic color trait. The phenotype was paler in color than the wild type, although not as pale as a previously described mutant strain, yellow (ye), and retained dark pigmentation in the eyes. This selected strain was named gold. Mendelian breeding experiments indicate a recessive biallelic inheritance. The strain has decreased fitness characteristics based on measurements of egg production and pupa size.
文摘Color polymorphisms have been traditionally attributed to apostatic selection.The perception of color depends on the visual system of the observer.Theoretical models predict that differently perceived degrees of conspicuousness by two predator and prey species may cause the evolution of polymorphisms in the presence of anti-apostatic and apostatic selection.The spider Gasteracantha cancriformis(Araneidae)possesses several conspicuous color morphs.In orb-web spiders,the prey attraction hypothesis states that conspicuous colors are prey lures that increase spider foraging success via flower mimicry.Therefore,polymorphism could be maintained if each morph attracted a different prey species(multiple prey hypothesis)and each spider mimicked a different flower color(flower mimicry hypothesis).Conspicuous colors could be a warning signal to predators because of the spider's hard abdomen and spines.Multiple predators could perceive morphs differently and exert different degrees of selective pressures(multiple predator hypothesis).We explored these 3 hypotheses using reflectance data and color vision modeling to estimate the chromatic and achromatic contrast of G.cancriformis morphs as perceived by several potential prey and predator taxa.Our results revealed that individual taxa perceive the conspicuousness of morphs differently.Therefore,the multiple prey hypothesis and,in part,the multiple predator hypothesis may explain the evolution of color polymorphism in G.cancriformis,even in the presence of anti-apostatic selection.The flower mimicry hypothesis received support by color metrics,but not by color vision models.Other parameters not evaluated by color vision models could also affect the perception of morphs and influence morph survival and polymorphism stability.
文摘Chemical defenses are frequently accompanied by salient color patterns actively avoided by predators,a phe-nomenon referred to as aposematism.However,the production of both chemical defenses and pigments is costly,and is thus expected to be reduced under mild predator pressure.In this work,I compared the size and coloration of parotoid glands(2 dorsal,external swollen structures that secrete toxins in toads)of male and female Epidalea calamita toads from agrosystems and from pine groves.I also quantified the predator attacks received by plas-ticine toad models,whose“parotoid glands”differed in size and color conspicuousness,exposed in each habitat.Predators avoided models with large and conspicuous parotoid glands,but models in agrosystems were more of-ten attacked.Concerning actual toads,agrosystem and male individuals had larger parotoid glands,presumably implying greater production of chemical defenses than in pine grove and female conspecifics.Thesefindings are aligned with previous research suggesting that both agrosystem toads and males in this system are subjected to a more intense predator pressure.Difference between parotoid gland and dorsum coloration was greater in agrosys-tem toads.A marked internal pattern could function as an aposematic signal,which could counteract increased predator pressure.
文摘Batesian mimicry is the process in which harmless species adopt the appearance of a dangerous, aposematic species.In some prey species,both Batesian mimetic and non-Batesian morphs coexist,presupposing that both morphs have to be evolutionarily advantageous.The viperine snake, Natrix maura,exhibits a zigzag dorsal pattern and antipredatory behavior that mimics European vipers.This snake also has a striped dorsal pattern that coexists with the zigzag pattern.We have examined whether individuals belonging to different geographically structured clades were more likely to exhibit a certain dorsal pattern,and whether the zigzag pattern has a protective function by exposing artificial snakes to predation in natural environments,in addition to comparing antipredatory behavior between zigzag and striped snakes also in natural environments.Our results indicate that the striped pattern was not geographically structured,but habitat-dependent.Aerial predators less frequently attacked zigzag plasticine models than striped or unpatterned models.We detected a shift in antipredator behavior between the 2 morphs,as Batesian mimicking N.maura responded to an approaching potential predator by remaining immobile or fleeing at shorter distances than did striped ones.We conclude that Batesian mimics maintain the cryptic and aposematic value by resembling vipers,whereas in open habitats the non-Batesian mimic has altered its antipredator behavior to maintain its fitness.
