Parasites impact host fitness and constitute an important selective pressure on the host's life history.According to parasite-mediated sexual selection,ornaments are presumed to honestly indicate immune capacity o...Parasites impact host fitness and constitute an important selective pressure on the host's life history.According to parasite-mediated sexual selection,ornaments are presumed to honestly indicate immune capacity or resistance against parasites,and the chooser sex(typically females)obtains an advantage by selecting more ornamented,thus more immunocompetent mates.Therefore,signalers mounting an immune response must allocate resources from the sexual signal to the immune system,hence reducing the expression of the ornament and becoming less attractive to the choosing sex.Here,we test this idea in the lizard Psammodromus algirus.We inoculated a subsample of males with lipopolysaccharide(LPS)of the cell wall of Escherichia coli,while others served as sham controls.The inoculation of LPS decreased the proportion of ergosterol(pro-vitamin D2)in femoral secretions,and chemosensory tests showed that the scent of LPS-inoculated males was less attractive to females than the scent of control males.Given that ergosterol is a precursor of vitamin D,which has physiological functions as an immune modulator,immunocompromised males likely needed to divert vitamin D to the immune system,reducing the allocation of ergosterol to secretions.In this way,females could detect“sick”males,preferring the apparently healthy males.Overall,our study shows that mounting an immune response is costly in terms of reduced attractiveness.Moreover,we disentangle the underlying mechanism,which involves an honest signal based on vitamin D allocation.展开更多
Parasite-mediated selection is widely believed to play a crucial role in maintaining the diversity of the major histocompatibility complex(MHC)genes,which is thought to be maintained through heterozygote advantage,rar...Parasite-mediated selection is widely believed to play a crucial role in maintaining the diversity of the major histocompatibility complex(MHC)genes,which is thought to be maintained through heterozygote advantage,rare-allele advantage,and fluctuating selection.However,the relationship between parasite pressure and MHC diversity has yielded inconsistent findings.These inconsistencies may arise from the influence of environmental factors and individual variations in traits on host–parasite interactions.To address these issues,our study extensively investigated populations of striped hamsters inhabiting regions characterized by environmental heterogeneity.The primary objective was to examine the universality of parasite-mediated selection mechanisms.Our observations revealed the presence of multiple parasite infections,accompanied by spatial and temporal variations in parasite communities and infection patterns among individual hamsters.Specifically,the temperature was found to influence all four parasite indices,while the presence of gamasid mites and parasite richness decreased with increasing precipitation.We also noted significant seasonal variation in parasite dynamics.Moreover,a significant sexual dimorphism was observed with males exhibiting a considerably higher parasite burden compared to their female counterparts.Lastly,we identified the maintenance of MHC polymorphism in striped hamsters as being driven by the heterozygote advantage and fluctuating selection mechanisms.This study underscores the significance of ecological processes in comprehending host–parasite systems and highlights the necessity of considering environmental factors and individual traits when elucidating the mechanisms underlying MHC diversity mediated by parasites.展开更多
In host-parasite coevolution,the parasite is selected to increase its infectivity while host is selected to resist the parasite infection.It is widely held that parasite-mediated sexual selection can further amplify t...In host-parasite coevolution,the parasite is selected to increase its infectivity while host is selected to resist the parasite infection.It is widely held that parasite-mediated sexual selection can further amplify the selective pressure on the host to overcome parasite infection.In this paper we focus on certain types of parasites,those that can impair the activity of the host immune function to prevent signs of sickness.We show that the effect of sexual selection can actually reduce the selective pressure on the host immune response to adapt to the parasite infection.We design a simple mathematical model for a population of sexually reproducing organism in which individuals are choosy,preferring traits that are correlated negatively with immune system activity.We introduce to this population a parasite that can suppress activation of the host's immune response.Our results show that even though the host immune system is likely to ultimately evolve and adapt to the parasite infection,when sexual selection is part of this process,it can slow down this evolution on the host and give the parasite more time to get established.展开更多
基金approved by the Andalusian Government according to the law for animal experimentation(ref.04/02/2019/012)issued to GMRsupported by a grant from the Spanish Society for Ethology and Evolutionary Ecology(SEEEE),issued to M.C.
文摘Parasites impact host fitness and constitute an important selective pressure on the host's life history.According to parasite-mediated sexual selection,ornaments are presumed to honestly indicate immune capacity or resistance against parasites,and the chooser sex(typically females)obtains an advantage by selecting more ornamented,thus more immunocompetent mates.Therefore,signalers mounting an immune response must allocate resources from the sexual signal to the immune system,hence reducing the expression of the ornament and becoming less attractive to the choosing sex.Here,we test this idea in the lizard Psammodromus algirus.We inoculated a subsample of males with lipopolysaccharide(LPS)of the cell wall of Escherichia coli,while others served as sham controls.The inoculation of LPS decreased the proportion of ergosterol(pro-vitamin D2)in femoral secretions,and chemosensory tests showed that the scent of LPS-inoculated males was less attractive to females than the scent of control males.Given that ergosterol is a precursor of vitamin D,which has physiological functions as an immune modulator,immunocompromised males likely needed to divert vitamin D to the immune system,reducing the allocation of ergosterol to secretions.In this way,females could detect“sick”males,preferring the apparently healthy males.Overall,our study shows that mounting an immune response is costly in terms of reduced attractiveness.Moreover,we disentangle the underlying mechanism,which involves an honest signal based on vitamin D allocation.
基金supported by the Key Program of National Natural Science Foundation of China[GRANT 32090023].
文摘Parasite-mediated selection is widely believed to play a crucial role in maintaining the diversity of the major histocompatibility complex(MHC)genes,which is thought to be maintained through heterozygote advantage,rare-allele advantage,and fluctuating selection.However,the relationship between parasite pressure and MHC diversity has yielded inconsistent findings.These inconsistencies may arise from the influence of environmental factors and individual variations in traits on host–parasite interactions.To address these issues,our study extensively investigated populations of striped hamsters inhabiting regions characterized by environmental heterogeneity.The primary objective was to examine the universality of parasite-mediated selection mechanisms.Our observations revealed the presence of multiple parasite infections,accompanied by spatial and temporal variations in parasite communities and infection patterns among individual hamsters.Specifically,the temperature was found to influence all four parasite indices,while the presence of gamasid mites and parasite richness decreased with increasing precipitation.We also noted significant seasonal variation in parasite dynamics.Moreover,a significant sexual dimorphism was observed with males exhibiting a considerably higher parasite burden compared to their female counterparts.Lastly,we identified the maintenance of MHC polymorphism in striped hamsters as being driven by the heterozygote advantage and fluctuating selection mechanisms.This study underscores the significance of ecological processes in comprehending host–parasite systems and highlights the necessity of considering environmental factors and individual traits when elucidating the mechanisms underlying MHC diversity mediated by parasites.
文摘In host-parasite coevolution,the parasite is selected to increase its infectivity while host is selected to resist the parasite infection.It is widely held that parasite-mediated sexual selection can further amplify the selective pressure on the host to overcome parasite infection.In this paper we focus on certain types of parasites,those that can impair the activity of the host immune function to prevent signs of sickness.We show that the effect of sexual selection can actually reduce the selective pressure on the host immune response to adapt to the parasite infection.We design a simple mathematical model for a population of sexually reproducing organism in which individuals are choosy,preferring traits that are correlated negatively with immune system activity.We introduce to this population a parasite that can suppress activation of the host's immune response.Our results show that even though the host immune system is likely to ultimately evolve and adapt to the parasite infection,when sexual selection is part of this process,it can slow down this evolution on the host and give the parasite more time to get established.
