Glucocorticoids(GCs)are involved in the regulation of an animal's energetic state.Under stressful situations,they are part of the neuroendocrine response to cope with environmental challenges.Animals react to aver...Glucocorticoids(GCs)are involved in the regulation of an animal's energetic state.Under stressful situations,they are part of the neuroendocrine response to cope with environmental challenges.Animals react to aversive stimuli also through behavioral responses,defined as coping styles.Both in captive and wild populations,individuals differ in their behavior along a proactive-reactive continuum.Proactive animals exhibit a bold,active explorative and social personality,whereas reactive ones areshy,less active-explorative and less social.Here,we test the hypothesis that personality traits and physiological responses to stressors covary,with more proactive individuals having a less pronounced GC stress response.In wild populations of invasive gray squirrels Sciurus carolinensis,we measuredfecal glucocorticoid metabolites(FGMs),an integrated measure of circulating GCs,and 3 personality traits(activity,sociability,and exploration)derived from open field test(OFT)and mirror image stimulation(MIS)test.Gray squirrels had higher FGMs in Autumn than in Winter and males with scrotal testes had higher FGMs than nonbreeding males.Personality varied with body mass and population density.Squirrels expressed more activity exploration at higher than at lower density and heavier squirrels had higher scores for activity exploration than animals that weighed less.Variation in FGM concentrations was not correlated with the expression of the 3 personality traits.Hence,our results do not support a strong association between the behavioral and physiological stress responses but show that in wild populations,where animals experience varying environmental conditions,the GC endocrine response and the expression of personality are uncorrelated traits among individuals.展开更多
Short-term elevation of glucocorticoids(GCs)is one of the major physiological mechanisms by which vertebrates cope with challenging environmental or social factors(stressors).However,when exposure to stressors occurs ...Short-term elevation of glucocorticoids(GCs)is one of the major physiological mechanisms by which vertebrates cope with challenging environmental or social factors(stressors).However,when exposure to stressors occurs repeatedly or over a prolonged period of time,animals may experience chronic elevation of GCs,which reduces the immune response efficiency and can lead to higher intensity of parasitic infection.Here,we used invasive gray squirrels Sciurus carolinensis in troduced in Norther n Italy and their 2 most prevale nt gastrointesti nal parasites,the n ematode Strongyloides robustus and coccidia of the genus Eimeria,as a model to investigate relati on ships among macroparasite infection and concentrations of fecal glucocorticoid metabolites(FGMs),an integrated measure of circulating GCs.Our results revealed an association of FGMs with infection by St.robustus,but not with coccidia.Individuals with higher FGMs appear to be responsible for the greatest St.robustus egg shedding within gray squirrel populations,thus possibly acting as superspreaders.However,FGMs were negatively associated with adult St.robustus,suggesting that the abundance of adults of this nematode species does not induce elevation in FGMs,but is only affected by it through immun e-mediated effects on its fecun dity.Fin ally,the relati on ship betwee n St.robustus(both eggs and adult parasites)and FGMs was not linear,suggesting that only high levels of physiological stress in fluence parasite inf ection.Our fin dings highlight that the direction and magnitude of the stress-infection relationship may depend not only on the specific hostparasite system,but also on the different life stages of the same parasite.展开更多
Integrative taxonomy,a multi-disciplinary approach adding modern techniques to traditional morphology-based methods(e.g.molecular and morphological criteria),can play an important role in bioinvasion research to ident...Integrative taxonomy,a multi-disciplinary approach adding modern techniques to traditional morphology-based methods(e.g.molecular and morphological criteria),can play an important role in bioinvasion research to identify introduced taxa,discover pathways of introduction and inform authorities to control and prevent future introductions.The present study is the first on introduced populations of Callosciurus,Asiatic tree squirrels,known as potentially invasive species in Europe(Italy,Belgium and France).We combined molecular(mitochondrial DNA markers:CoxI,D-loop)and morphometric analysis on skulls,comparing them to the widest morphological and molecular datasets ever assembled for Callosciurus.Squirrels collected in Italy and Belgium share the same haplotypes and skull characteristics,but are conspicuously different from the French population in Antibes.Genetic data revealed close similarity between French squirrels and Pallas’s squirrels,Callosciurus erythraeus,from Taiwan,China.Italian and Belgian squirrels formed an independent taxonomic lineage in genetic analyses,whose taxonomic rank needs further investigation.The morphological and morphometric characteristics of these 2 populations are,however,similar to known specimens assigned to Callosciurus erythraeus.These results may indicate a common origin for the populations found in Belgium and Italy.In contrast,French specimens suggest an independent introduction event of squirrels originating from Asia.展开更多
文摘Glucocorticoids(GCs)are involved in the regulation of an animal's energetic state.Under stressful situations,they are part of the neuroendocrine response to cope with environmental challenges.Animals react to aversive stimuli also through behavioral responses,defined as coping styles.Both in captive and wild populations,individuals differ in their behavior along a proactive-reactive continuum.Proactive animals exhibit a bold,active explorative and social personality,whereas reactive ones areshy,less active-explorative and less social.Here,we test the hypothesis that personality traits and physiological responses to stressors covary,with more proactive individuals having a less pronounced GC stress response.In wild populations of invasive gray squirrels Sciurus carolinensis,we measuredfecal glucocorticoid metabolites(FGMs),an integrated measure of circulating GCs,and 3 personality traits(activity,sociability,and exploration)derived from open field test(OFT)and mirror image stimulation(MIS)test.Gray squirrels had higher FGMs in Autumn than in Winter and males with scrotal testes had higher FGMs than nonbreeding males.Personality varied with body mass and population density.Squirrels expressed more activity exploration at higher than at lower density and heavier squirrels had higher scores for activity exploration than animals that weighed less.Variation in FGM concentrations was not correlated with the expression of the 3 personality traits.Hence,our results do not support a strong association between the behavioral and physiological stress responses but show that in wild populations,where animals experience varying environmental conditions,the GC endocrine response and the expression of personality are uncorrelated traits among individuals.
基金Thanks to Zainab Almusawi and Teera Losch for helping in laboratory analysis,Candice Gagnaison,Laure Vanlauwe,and Mattia Panzeri for assistance with the fieldwork.We are grateful to the private land owners for access to their estates.Three anonymous reviewers provided constructive comments that helped us to improve the article.
文摘Short-term elevation of glucocorticoids(GCs)is one of the major physiological mechanisms by which vertebrates cope with challenging environmental or social factors(stressors).However,when exposure to stressors occurs repeatedly or over a prolonged period of time,animals may experience chronic elevation of GCs,which reduces the immune response efficiency and can lead to higher intensity of parasitic infection.Here,we used invasive gray squirrels Sciurus carolinensis in troduced in Norther n Italy and their 2 most prevale nt gastrointesti nal parasites,the n ematode Strongyloides robustus and coccidia of the genus Eimeria,as a model to investigate relati on ships among macroparasite infection and concentrations of fecal glucocorticoid metabolites(FGMs),an integrated measure of circulating GCs.Our results revealed an association of FGMs with infection by St.robustus,but not with coccidia.Individuals with higher FGMs appear to be responsible for the greatest St.robustus egg shedding within gray squirrel populations,thus possibly acting as superspreaders.However,FGMs were negatively associated with adult St.robustus,suggesting that the abundance of adults of this nematode species does not induce elevation in FGMs,but is only affected by it through immun e-mediated effects on its fecun dity.Fin ally,the relati on ship betwee n St.robustus(both eggs and adult parasites)and FGMs was not linear,suggesting that only high levels of physiological stress in fluence parasite inf ection.Our fin dings highlight that the direction and magnitude of the stress-infection relationship may depend not only on the specific hostparasite system,but also on the different life stages of the same parasite.
文摘Integrative taxonomy,a multi-disciplinary approach adding modern techniques to traditional morphology-based methods(e.g.molecular and morphological criteria),can play an important role in bioinvasion research to identify introduced taxa,discover pathways of introduction and inform authorities to control and prevent future introductions.The present study is the first on introduced populations of Callosciurus,Asiatic tree squirrels,known as potentially invasive species in Europe(Italy,Belgium and France).We combined molecular(mitochondrial DNA markers:CoxI,D-loop)and morphometric analysis on skulls,comparing them to the widest morphological and molecular datasets ever assembled for Callosciurus.Squirrels collected in Italy and Belgium share the same haplotypes and skull characteristics,but are conspicuously different from the French population in Antibes.Genetic data revealed close similarity between French squirrels and Pallas’s squirrels,Callosciurus erythraeus,from Taiwan,China.Italian and Belgian squirrels formed an independent taxonomic lineage in genetic analyses,whose taxonomic rank needs further investigation.The morphological and morphometric characteristics of these 2 populations are,however,similar to known specimens assigned to Callosciurus erythraeus.These results may indicate a common origin for the populations found in Belgium and Italy.In contrast,French specimens suggest an independent introduction event of squirrels originating from Asia.
