Aims A plethora of theories explain species invasion,yet when tested in isolation,support or falsification becomes contingent on study species,system and approach.Our objective was to examine com-munity-level species ...Aims A plethora of theories explain species invasion,yet when tested in isolation,support or falsification becomes contingent on study species,system and approach.Our objective was to examine com-munity-level species invasion as a function of multiple competing hypotheses.Methods We used data from>3500 woodland plant species in 2750 plots in 49 national parks in eastern US deciduous forests to test multiple competing theories of species invasion:competition,empty niche,propagule pressure and latitude matching.We also tested interac-tions with residence time to account for non-native species naturali-zation and spread since arrival.Important Findings The non-native herbs generally thrived at latitudes similar to those from which they originated,but not necessarily where they were originally introduced to the eastern US.Overall,we found that each hypothesis explained at least some aspect of woodland plant species invasion,but examining them simultaneously allowed assessment of their relative strengths and interactions.Our results suggested that residence time is a strong predictor of non-native woodland plant success,particularly as it interacts with other mechanisms of inva-sion,such as competition(abundance of native woodland plants),climate matching(similar invaded latitude as home range),prop-agule pressure(distance to putative seed sources)and empty niche(relatedness to native plants).We found that initial barriers,such as distance from propagule source or suboptimal habitat,were over-come,as was resistance from native relatives.However,the biggest challenge for the non-native woodland plants appeared to be time,as they declined after~1 to 2 centuries.展开更多
Aims Possible shifts in the phenotypic performance along invasive plants’spreading route are rarely examined due to the discontinuous and incomplete records of exotic species.As the invasion history of common ragweed...Aims Possible shifts in the phenotypic performance along invasive plants’spreading route are rarely examined due to the discontinuous and incomplete records of exotic species.As the invasion history of common ragweed(Ambrosia artemisiifolia L.)is well documented in Hungary,its residence time is known for each location.By sampling a sequence of older to more recently established populations,we aimed to determine(i)whether there are phenotypic divergences along the historical spreading route of A.artemisiifolia;(ii)which traits are under selection during the invasion process and(iii)the extent of maternal effects on the individual’s performance.Methods We used a hierarchical sampling design to collect seeds from 64 individuals belonging to eight sites in four residence time categories(seven populations along the historical spreading route of ragweed in Hungary and one recently invaded site in Romania).We selected four large and four small individual plants in each population to control for maternal effects.The offspring were reared in a common garden located in Romania.Five vegetative phenotypic traits were measured at the end of the experiments and used in the subsequent analysis(plant height,basal diameter,number of secondary axes,length of the longest secondary axis and biomass).To summarize the variation of these highly correlated traits,principal component analysis was performed first and then the important components were used in linear mixed effect models.Important Findings The residence time categories were significantly distinguished by the first component,which compresses the variation of all five measured traits.The measures gradually decrease from populations with the longest residence time(introduced more than 65 years ago)towards the most recently established populations(established less than 30 years ago).These differences might reflect the invasion history of the populations:the longer the residence time the higher the chance to develop relevant traits beneficial in invasion process.The size of 展开更多
文摘Aims A plethora of theories explain species invasion,yet when tested in isolation,support or falsification becomes contingent on study species,system and approach.Our objective was to examine com-munity-level species invasion as a function of multiple competing hypotheses.Methods We used data from>3500 woodland plant species in 2750 plots in 49 national parks in eastern US deciduous forests to test multiple competing theories of species invasion:competition,empty niche,propagule pressure and latitude matching.We also tested interac-tions with residence time to account for non-native species naturali-zation and spread since arrival.Important Findings The non-native herbs generally thrived at latitudes similar to those from which they originated,but not necessarily where they were originally introduced to the eastern US.Overall,we found that each hypothesis explained at least some aspect of woodland plant species invasion,but examining them simultaneously allowed assessment of their relative strengths and interactions.Our results suggested that residence time is a strong predictor of non-native woodland plant success,particularly as it interacts with other mechanisms of inva-sion,such as competition(abundance of native woodland plants),climate matching(similar invaded latitude as home range),prop-agule pressure(distance to putative seed sources)and empty niche(relatedness to native plants).We found that initial barriers,such as distance from propagule source or suboptimal habitat,were over-come,as was resistance from native relatives.However,the biggest challenge for the non-native woodland plants appeared to be time,as they declined after~1 to 2 centuries.
基金The research was supported by a PhD scholarship of the Hungarian Ministry of Education(A.F.)a scholarship(no.2008/A/19 E)of the Hungarian Academy of Sciences(A.F.).
文摘Aims Possible shifts in the phenotypic performance along invasive plants’spreading route are rarely examined due to the discontinuous and incomplete records of exotic species.As the invasion history of common ragweed(Ambrosia artemisiifolia L.)is well documented in Hungary,its residence time is known for each location.By sampling a sequence of older to more recently established populations,we aimed to determine(i)whether there are phenotypic divergences along the historical spreading route of A.artemisiifolia;(ii)which traits are under selection during the invasion process and(iii)the extent of maternal effects on the individual’s performance.Methods We used a hierarchical sampling design to collect seeds from 64 individuals belonging to eight sites in four residence time categories(seven populations along the historical spreading route of ragweed in Hungary and one recently invaded site in Romania).We selected four large and four small individual plants in each population to control for maternal effects.The offspring were reared in a common garden located in Romania.Five vegetative phenotypic traits were measured at the end of the experiments and used in the subsequent analysis(plant height,basal diameter,number of secondary axes,length of the longest secondary axis and biomass).To summarize the variation of these highly correlated traits,principal component analysis was performed first and then the important components were used in linear mixed effect models.Important Findings The residence time categories were significantly distinguished by the first component,which compresses the variation of all five measured traits.The measures gradually decrease from populations with the longest residence time(introduced more than 65 years ago)towards the most recently established populations(established less than 30 years ago).These differences might reflect the invasion history of the populations:the longer the residence time the higher the chance to develop relevant traits beneficial in invasion process.The size of
