Aims The superior performance of many non-indigenous species in a new range can be attributed to different factors such as pre-adaptation to environmental conditions in new areas or to factors inherent to displacement...Aims The superior performance of many non-indigenous species in a new range can be attributed to different factors such as pre-adaptation to environmental conditions in new areas or to factors inherent to displacement mechanisms such as loss of co-evolved pathogens and herbivores that increase the speed of evolutionary change towards a shift in allocation from defence to growth and reproduction.To assess the importance of the different mechanisms governing the success of Conyza canadensis,a globally successful invader,we simultaneously tested several recent hypotheses potentially explaining the factors leading to biological invasion.Methods We tested(i)whether plants from the non-native range showed a higher fitness than plants from the native North American range,(ii)whether they differed in resistance against an invasive generalist herbivore,the slug Arion lusitanicus and against a recently established specialist aphid herbivore,Uroleucon erigeronense and(iii)experimentally assessed whether C.canadensis releases allelopathic chemicals that have harmful effects on competing species in the nonnative range.We compared populations along a similar latitudinal gradient both in the native North American and invasive European range and analysed patterns of adaptive clinal variation in biomass production.Important Findings The invasion success of C.canadensis in Europe cannot be attributed to a single trait,but to a combination of factors.Invasive plants benefited from increased growth and above all,increased reproduction(a key trait in an annual plant)and were less attacked by a co-migrated specialist enemy.The observed loss of defence against generalist slugs did not translate into a decreased fitness as invasive C.canadensis plants showed a high re-growth potential.In contrast to earlier in vitro studies,we detected no allelopathic effects on the competing flora in the non-native range.The latitudinal cline in vegetative biomass production in the non-native range observed in our common garden study indicates a high adaptive potential.However,only further genetic studies will provide conclusive evidence whether the differentiation in the non-native range is caused by pre-adaptation and sorting-out processes of putatively repeatedly introduced populations of this composite,long-distance disperser with highly volatile seeds or evolved de novo as a rapid response to new selection pressures in the nonnative range.展开更多
Plant invasions create novel plant-insect interactions. The EICA （evolution of increased competitive ability） hypothesis proposes that invasive plants will reallocate resources from defense to growth and/or reproduc...Plant invasions create novel plant-insect interactions. The EICA （evolution of increased competitive ability） hypothesis proposes that invasive plants will reallocate resources from defense to growth and/or reproduction because they have escaped from their co-evolved insect natural enemies. Testing multiple herbivory by monophagous and oligophagous herbivores and simultaneous measurement of various plant traits will provide new insights into the evolutionary change ofinvasive plants. In this context, we conducted a common garden experiment to compare plant growth and reproduction, chemical and physical defense, and plant responses to herbivory by different types of herbivores between invasive North American populations and native East Asian populations of mile-a-minute weed, Persicariaperfoliata. We found that invasive mile-a-minnte exhibited lower biomass, flowered earlier and had greater reproductive output than plants from the native range. Compared with native populations, plants from invasive populations had lower tannin content, but exhibited higher prickle density on nodes and leaves. Thus our results partially support the EICA hypothesis. When exposed to the monophagous insect, Rhinoncomimus latipes and the oligophagous insects, Gallerucida grisescens and Smaragdina nigrifrons, more damage by herbivory was found on invasive plants than on natives. R. latipes, G. grisescens and S. nigrifrons had strong, moderate and weak impacts on the growth and reproduction of mile-a-minute, respectively. The results indicate that mile-a-minute may have evolved a higher reproductive capacity in the introduced range, and this along with a lack of oligophagous and monophagous herbivores in the new range may have contributed to its invasiveness in North America.展开更多
Trade-offs between performance and tolerance of abiotic and biotic stress have been proposed to explain both the success of invasive species and frequently observed size differences between native and introduced popul...Trade-offs between performance and tolerance of abiotic and biotic stress have been proposed to explain both the success of invasive species and frequently observed size differences between native and introduced populations.Canada thistle seeds collected from across the introduced North American and the native European range were grown in benign and stressful conditions(nutrient stress,shading,simulated herbivory,drought,and mowing),to evaluate whether native and introduced individuals differ in performance or stress tolerance.An additional experiment assessed the strength of maternal effects by comparing plants derived from field-collected seeds with those derived from clones grown in the glasshouse.Introduced populations tended to be larger in size,but no trade-off of stress tolerance with performance was detected;introduced populations had either superior performance or equivalent trait values and survivorship in the treatment common gardens.We also detected evidence of parallel latitudinal clines of some traits in both the native and introduced ranges and associations with climate variables in some treatments,consistent with recent climate adaptation within the introduced range.Our results are consistent with rapid adaptation of introduced populations,but,contrary to predictions,the evolution of invasive traits did not come at the cost of reduced stress tolerance.展开更多
基金This work was supported by a grant from the Swiss National Science Foundation to J.J.(nr.3100AO-104006).
文摘Aims The superior performance of many non-indigenous species in a new range can be attributed to different factors such as pre-adaptation to environmental conditions in new areas or to factors inherent to displacement mechanisms such as loss of co-evolved pathogens and herbivores that increase the speed of evolutionary change towards a shift in allocation from defence to growth and reproduction.To assess the importance of the different mechanisms governing the success of Conyza canadensis,a globally successful invader,we simultaneously tested several recent hypotheses potentially explaining the factors leading to biological invasion.Methods We tested(i)whether plants from the non-native range showed a higher fitness than plants from the native North American range,(ii)whether they differed in resistance against an invasive generalist herbivore,the slug Arion lusitanicus and against a recently established specialist aphid herbivore,Uroleucon erigeronense and(iii)experimentally assessed whether C.canadensis releases allelopathic chemicals that have harmful effects on competing species in the nonnative range.We compared populations along a similar latitudinal gradient both in the native North American and invasive European range and analysed patterns of adaptive clinal variation in biomass production.Important Findings The invasion success of C.canadensis in Europe cannot be attributed to a single trait,but to a combination of factors.Invasive plants benefited from increased growth and above all,increased reproduction(a key trait in an annual plant)and were less attacked by a co-migrated specialist enemy.The observed loss of defence against generalist slugs did not translate into a decreased fitness as invasive C.canadensis plants showed a high re-growth potential.In contrast to earlier in vitro studies,we detected no allelopathic effects on the competing flora in the non-native range.The latitudinal cline in vegetative biomass production in the non-native range observed in our common garden study indicates a high adaptive potential.However,only further genetic studies will provide conclusive evidence whether the differentiation in the non-native range is caused by pre-adaptation and sorting-out processes of putatively repeatedly introduced populations of this composite,long-distance disperser with highly volatile seeds or evolved de novo as a rapid response to new selection pressures in the nonnative range.
文摘Plant invasions create novel plant-insect interactions. The EICA （evolution of increased competitive ability） hypothesis proposes that invasive plants will reallocate resources from defense to growth and/or reproduction because they have escaped from their co-evolved insect natural enemies. Testing multiple herbivory by monophagous and oligophagous herbivores and simultaneous measurement of various plant traits will provide new insights into the evolutionary change ofinvasive plants. In this context, we conducted a common garden experiment to compare plant growth and reproduction, chemical and physical defense, and plant responses to herbivory by different types of herbivores between invasive North American populations and native East Asian populations of mile-a-minute weed, Persicariaperfoliata. We found that invasive mile-a-minnte exhibited lower biomass, flowered earlier and had greater reproductive output than plants from the native range. Compared with native populations, plants from invasive populations had lower tannin content, but exhibited higher prickle density on nodes and leaves. Thus our results partially support the EICA hypothesis. When exposed to the monophagous insect, Rhinoncomimus latipes and the oligophagous insects, Gallerucida grisescens and Smaragdina nigrifrons, more damage by herbivory was found on invasive plants than on natives. R. latipes, G. grisescens and S. nigrifrons had strong, moderate and weak impacts on the growth and reproduction of mile-a-minute, respectively. The results indicate that mile-a-minute may have evolved a higher reproductive capacity in the introduced range, and this along with a lack of oligophagous and monophagous herbivores in the new range may have contributed to its invasiveness in North America.
基金supported by grants(PBZHP3-123301 and PA00P3_134180)from the Swiss National Science Foundation to A.G.from the Natural Sciences and Engineering Research Council of Canada Awards(327475 and 353026)to L.H.R.
文摘Trade-offs between performance and tolerance of abiotic and biotic stress have been proposed to explain both the success of invasive species and frequently observed size differences between native and introduced populations.Canada thistle seeds collected from across the introduced North American and the native European range were grown in benign and stressful conditions(nutrient stress,shading,simulated herbivory,drought,and mowing),to evaluate whether native and introduced individuals differ in performance or stress tolerance.An additional experiment assessed the strength of maternal effects by comparing plants derived from field-collected seeds with those derived from clones grown in the glasshouse.Introduced populations tended to be larger in size,but no trade-off of stress tolerance with performance was detected;introduced populations had either superior performance or equivalent trait values and survivorship in the treatment common gardens.We also detected evidence of parallel latitudinal clines of some traits in both the native and introduced ranges and associations with climate variables in some treatments,consistent with recent climate adaptation within the introduced range.Our results are consistent with rapid adaptation of introduced populations,but,contrary to predictions,the evolution of invasive traits did not come at the cost of reduced stress tolerance.
