Aims in this study,we examine two common invasion biology hypotheses-biotic resistance and fluctuating resource availability-to explain the patterns of invasion of an invasive grass,Microstegium vimineum.Methods We us...Aims in this study,we examine two common invasion biology hypotheses-biotic resistance and fluctuating resource availability-to explain the patterns of invasion of an invasive grass,Microstegium vimineum.Methods We used 13-year-old deer exclosures in great smoky mountains National Park,USA,to examine how chronic disturbance by deer browsing affects available resources,plant diversity,and invasion in an understory plant community.using two replicate 1 m2 plots in each deer browsed and unbrowsed area,we recorded each plant species present,the abundance per species,and the fractional per-cent cover of vegetation by the cover classes:herbaceous,woody,and graminoid.For each sample plot,we also estimated overstory canopy cover,soil moisture,total soil carbon and nitrogen,and soil pH as a measure of abiotic differences between plots.Important Findings We found that plant community composition between chronically browsed and unbrowsed plots differed markedly.Plant diversity was 40%lower in browsed than in unbrowsed plots.at our sites,diver-sity explained 48%and woody plant cover 35%of the variation in M.vimineum abundance.in addition,we found 3.3 times less M.vimineum in the unbrowsed plots due to higher woody plant cover and plant diversity than in the browsed plots.a parsimonious explanation of these results indicate that disturbances such as herbivory may elicit multiple conditions,namely releasing available resources such as open space,light,and decreasing plant diversity,which may facilitate the proliferation of an invasive species.Finally,by testing two different hypotheses,this study addresses more recent calls to incorporate multiple hypotheses into research attempting to explain plant invasion.展开更多
Aims While a growing number of studies have demonstrated the impor-tance of intraspecific differences within plant species on associ-ated arthropod communities,little is known regarding the relative strength of these ...Aims While a growing number of studies have demonstrated the impor-tance of intraspecific differences within plant species on associ-ated arthropod communities,little is known regarding the relative strength of these effects compared to environmental factors.In this study,we examined whether intraspecific plant differences and nutrient fertilization interact to shape the arthropod community of a dominant coastal shrub,Baccharis pilularis(coyote bush).Methods We overlaid a fertilization treatment on a 12-year-old common garden experiment planted with erect and prostrate architectural morphs of Baccharis in california,USA.to collect the associated arthropod community,we vacuum sampled the crown of each Baccharis and identified individuals to species or morphospecies.Important Findings We found that arthropod richness and abundance were 2-to 3-fold greater on prostrate Baccharis than on erect morphs,but observed no main effects of fertilizer addition on the over-all arthropod communities.Predators responded as strongly as herbivores to plant morph,and both were unaffected by nutrient additions.Only the specialist stem galler,Gnorimoschema bac-charisella,showed an interactive response to plant morph and fertilization.Nitrogen,phosphorous and potassium addition had opposite effects on the two morphs,increasing stem gall abun-dance by 50%on prostrate morphs,but reducing galling by 20%on erect morphs.the architectural complexity of prostrate morphs could be the driving mechanism of differences in arthropod assemblages.Overall,our results demonstrate that communitylevel consequences of intraspecific differences in plants are strong,rather than being context dependent,and are generally maintained under different resource environments.the growing number of studies showing strong genotype than nutrient effects on associated arthropod communities suggests that this might be a generalized pattern.展开更多
文摘Aims in this study,we examine two common invasion biology hypotheses-biotic resistance and fluctuating resource availability-to explain the patterns of invasion of an invasive grass,Microstegium vimineum.Methods We used 13-year-old deer exclosures in great smoky mountains National Park,USA,to examine how chronic disturbance by deer browsing affects available resources,plant diversity,and invasion in an understory plant community.using two replicate 1 m2 plots in each deer browsed and unbrowsed area,we recorded each plant species present,the abundance per species,and the fractional per-cent cover of vegetation by the cover classes:herbaceous,woody,and graminoid.For each sample plot,we also estimated overstory canopy cover,soil moisture,total soil carbon and nitrogen,and soil pH as a measure of abiotic differences between plots.Important Findings We found that plant community composition between chronically browsed and unbrowsed plots differed markedly.Plant diversity was 40%lower in browsed than in unbrowsed plots.at our sites,diver-sity explained 48%and woody plant cover 35%of the variation in M.vimineum abundance.in addition,we found 3.3 times less M.vimineum in the unbrowsed plots due to higher woody plant cover and plant diversity than in the browsed plots.a parsimonious explanation of these results indicate that disturbances such as herbivory may elicit multiple conditions,namely releasing available resources such as open space,light,and decreasing plant diversity,which may facilitate the proliferation of an invasive species.Finally,by testing two different hypotheses,this study addresses more recent calls to incorporate multiple hypotheses into research attempting to explain plant invasion.
基金EEB summer grants from the Department of Ecology and Evolutionary Biology,University of Tennessee(to M.N.B.-G.and M.A.R.-C.)the Miller Institute for Basic Research in Science(to G.M.C.).
文摘Aims While a growing number of studies have demonstrated the impor-tance of intraspecific differences within plant species on associ-ated arthropod communities,little is known regarding the relative strength of these effects compared to environmental factors.In this study,we examined whether intraspecific plant differences and nutrient fertilization interact to shape the arthropod community of a dominant coastal shrub,Baccharis pilularis(coyote bush).Methods We overlaid a fertilization treatment on a 12-year-old common garden experiment planted with erect and prostrate architectural morphs of Baccharis in california,USA.to collect the associated arthropod community,we vacuum sampled the crown of each Baccharis and identified individuals to species or morphospecies.Important Findings We found that arthropod richness and abundance were 2-to 3-fold greater on prostrate Baccharis than on erect morphs,but observed no main effects of fertilizer addition on the over-all arthropod communities.Predators responded as strongly as herbivores to plant morph,and both were unaffected by nutrient additions.Only the specialist stem galler,Gnorimoschema bac-charisella,showed an interactive response to plant morph and fertilization.Nitrogen,phosphorous and potassium addition had opposite effects on the two morphs,increasing stem gall abun-dance by 50%on prostrate morphs,but reducing galling by 20%on erect morphs.the architectural complexity of prostrate morphs could be the driving mechanism of differences in arthropod assemblages.Overall,our results demonstrate that communitylevel consequences of intraspecific differences in plants are strong,rather than being context dependent,and are generally maintained under different resource environments.the growing number of studies showing strong genotype than nutrient effects on associated arthropod communities suggests that this might be a generalized pattern.
