No evidence for local adaptation in an invasive alien plant: field and greenhouse experiments tracing a colonization sequence.
OBJECTIVE
Local adaptation enables plant species to persist under different environmental conditions. Evolutionary change can occur rapidly in invasive annual species and has been shown to lead to local adaptation. However, the patterns and mechanisms of local adaptation in invasive species along colonization sequences are not yet understood. Thus, in this study the alien annual Impatiens glandulifera was used to investigate local adaptation to distinct habitats that have been consecutively invaded in central Europe.


METHODS
A reciprocal transplant experiment was performed using 15 populations from alluvial deciduous forests, fallow meadows and coniferous upland forests, and a greenhouse experiment was performed in which plants from these habitats were grown under treatments reflecting the main habitat differentiators (shade, soil acidity, competition).


RESULTS
Biomass production, specific leaf area, plant height and relative growth rate differed between habitats in the field experiment and between treatments in the greenhouse, but not between seed origins. Overall, there was no indication of local adaptation in either experiment.


CONCLUSIONS
Since I. glandulifera is a successful invader in many habitats without showing local adaptation, it is suggested that the species is coping with environmental variation by means of high phenotypic plasticity. The species seems to follow a 'jack-and-master' strategy, i.e. it is able to maintain high fitness under a wide range of environmental conditions, but performs particularly well in favourable habitats. Therefore, the proposed colonization sequence is likely to be based primarily on changes in propagule pressure. It is concluded that invasive alien plants can become dominant in distinct habitats without local adaptation.
Restoration Ecology, Technische Universität München, D-85350 Freising-Weihenstephan, Germany.
Anna T
AT
Pahl
Johannes
J
Kollmann
Andreas
A
Mayer
Sylvia
S
Haider
D000220:Adaptation, Biological; D006863:Hydrogen-Ion Concentration; D029069:Impatiens / Q000502:physiology*; D058865:Introduced Species; D008027:Light; D012987:Soil
D012987:Soil
Biological invasions; Impatiens glandulifera; colonization history; general-purpose genotype; greenhouse experiment; home site advantage; invasive alien plant; jack-and-master strategy; local adaptation; phenotypic plasticity; propagule pressure; reciprocal transplant experiment