Recent research often lauds the services and beneficial effects of host-associated microbes on animals.However,hosting these microbes may come at a cost.For example,germ-free and antibiotic-treated birds generally gro...Recent research often lauds the services and beneficial effects of host-associated microbes on animals.However,hosting these microbes may come at a cost.For example,germ-free and antibiotic-treated birds generally grow faster than their conventional counterparts.In the wild,juvenile body size is correlated with survival,so hosting a microbiota may incur a fitness cost.Avian altricial nestlings represent an interesting study system in which to investigate these interactions,given that they exhibit the fastest growth rates among vertebrates,and growth is limited by their digestive capacity.We investigated whether reduction and restructuring of the microbiota by antibiotic treatment would:(i)increase growth and food conversion efficiency in nestling house sparrows(Passer domesticus);(ii)alter aspects of gut anatomy or function(particularly activities of digestive carbohydrases and their regulation in response to dietary change);and(iii)whether there were correlations between relative abundances of microbial taxa,digestive function and nestling growth.Antibiotic treatment significantly increased growth and food conversion efficiency in nestlings.Antibiotics did not alter aspects of gut anatomy that we considered but depressed intestinal maltase activity.There were no significant correlations between abundances of microbial taxa and aspects of host physiology.Overall,we conclude that microbial-induced growth limitation in developing birds is not driven by interactions with digestive capacity.Rather,decreased energetic and material costs of immune function or beneficial effects from microbes enriched under antibiotic treatment may underlie these effects.Understanding the costs and tradeoffs of hosting gut microbial communities represents an avenue of future research.展开更多
Aims Epiphytes are an abundant and diverse component of many wet temperate forests and have significant roles in ecosystem processes.Little is known about the processes and rates of their death and decomposition when ...Aims Epiphytes are an abundant and diverse component of many wet temperate forests and have significant roles in ecosystem processes.Little is known about the processes and rates of their death and decomposition when they fall from the canopy,which limits our understanding of their role in forest carbon sequestration and nutri-ent cycling.In the temperate rainforest of the Quinault River Valley,Washington State,our aim was to test hypotheses regarding four elements of disturbance that might contribute to their decline.Methods We established set of experiments in which we placed samples of canopy epiphytes and their branch segments:(i)in the canopy versus forest floor microenvironment(stratum);(ii)attached to live versus dead branch substrates;(iii)subjected to physical disruption and‘jarring’;and(iv)in direct versus indirect con-tact with the forest floor.Over the 2-year study,we assigned a non-destructive‘vitality index’(based on color and appar-ent mortality and dryness)to each sample every 2-3 months to compare effects of the experimental treatments and analyzed with a statistical model and post hoc pairwise comparisons of treatments.Important Findings The canopy versus ground stratum and live/dead branch status sig-nificantly affected epiphyte vitality.Effects of physical disruption and ground contact were not significant.There were seasonal effects(low vitality during the sampling times in the summer,revitalization upon sampling times in the winter)for all treatments except samples in contact with the ground.One implication of these results relates to effects of climate change,which is predicted to shift to hotter,drier summers and wetter winters.Climate change may affect forest dynamics and nutrient cycling in unpredictable ways.Results also point to future experiments to understand biotic and abiotic effects on epiphyte disturbance and dynamics.展开更多
基金Funding was provided by the National Science Foundation(IOS1354893 to W.H.K.)the National Institutes of Health(T32DK007673 Training Grant to K.D.K.)grants from Consejo Nacional de Investigaciones Científicas y Técnicas PIP 834 and UNSL CyT 9502 to E.C.V.
文摘Recent research often lauds the services and beneficial effects of host-associated microbes on animals.However,hosting these microbes may come at a cost.For example,germ-free and antibiotic-treated birds generally grow faster than their conventional counterparts.In the wild,juvenile body size is correlated with survival,so hosting a microbiota may incur a fitness cost.Avian altricial nestlings represent an interesting study system in which to investigate these interactions,given that they exhibit the fastest growth rates among vertebrates,and growth is limited by their digestive capacity.We investigated whether reduction and restructuring of the microbiota by antibiotic treatment would:(i)increase growth and food conversion efficiency in nestling house sparrows(Passer domesticus);(ii)alter aspects of gut anatomy or function(particularly activities of digestive carbohydrases and their regulation in response to dietary change);and(iii)whether there were correlations between relative abundances of microbial taxa,digestive function and nestling growth.Antibiotic treatment significantly increased growth and food conversion efficiency in nestlings.Antibiotics did not alter aspects of gut anatomy that we considered but depressed intestinal maltase activity.There were no significant correlations between abundances of microbial taxa and aspects of host physiology.Overall,we conclude that microbial-induced growth limitation in developing birds is not driven by interactions with digestive capacity.Rather,decreased energetic and material costs of immune function or beneficial effects from microbes enriched under antibiotic treatment may underlie these effects.Understanding the costs and tradeoffs of hosting gut microbial communities represents an avenue of future research.
基金National Science Foundation(EHR 15-14494 and DEB 11-41833 to N.M.N.and DBI 1400456 to K.D.K.).
文摘Aims Epiphytes are an abundant and diverse component of many wet temperate forests and have significant roles in ecosystem processes.Little is known about the processes and rates of their death and decomposition when they fall from the canopy,which limits our understanding of their role in forest carbon sequestration and nutri-ent cycling.In the temperate rainforest of the Quinault River Valley,Washington State,our aim was to test hypotheses regarding four elements of disturbance that might contribute to their decline.Methods We established set of experiments in which we placed samples of canopy epiphytes and their branch segments:(i)in the canopy versus forest floor microenvironment(stratum);(ii)attached to live versus dead branch substrates;(iii)subjected to physical disruption and‘jarring’;and(iv)in direct versus indirect con-tact with the forest floor.Over the 2-year study,we assigned a non-destructive‘vitality index’(based on color and appar-ent mortality and dryness)to each sample every 2-3 months to compare effects of the experimental treatments and analyzed with a statistical model and post hoc pairwise comparisons of treatments.Important Findings The canopy versus ground stratum and live/dead branch status sig-nificantly affected epiphyte vitality.Effects of physical disruption and ground contact were not significant.There were seasonal effects(low vitality during the sampling times in the summer,revitalization upon sampling times in the winter)for all treatments except samples in contact with the ground.One implication of these results relates to effects of climate change,which is predicted to shift to hotter,drier summers and wetter winters.Climate change may affect forest dynamics and nutrient cycling in unpredictable ways.Results also point to future experiments to understand biotic and abiotic effects on epiphyte disturbance and dynamics.
