High genetic diversity of introduced plant populations may pose a key advantage under changed selection
pressures but may also have important implications for biological control of such plants. However,
molecular markers employed to measure genetic variation do not necessarily reflect variations in phenotypic
traits such as plant chemical composition, which may be similarly important for both the invasion
success of a plant and the establishment of biological control agents. The Asteraceae species Tanacetum
vulgare is of Eurasian origin, but was introduced to North America, where it became invasive in some
areas. This species varies greatly in terpene composition, forming different chemotypes. To assess the
genetic diversity of T. vulgare in relation to its chemical diversity, we grew populations originating from
different sources of the native and introduced ranges under standardized conditions. Using inter simple
sequence repeat markers, we found indications for an increased genetic diversity in plants of the introduced
compared to the native range. Analyses of volatile profiles of these individuals indicated similarly
high chemical diversities in native and introduced populations. Clustering analyses revealed a considerable
amount of unique geno- and chemo-types on both continents. No significant relation between the
genetic and chemical data could be detected, demonstrating that the genetic structure of invasive populations
does not necessarily offer information on its chemical diversity and vice versa. Knowledge of both
the genetic structure and the actual variation in plant chemistry allows biological control research to consider
factors potentially interfering with the success of biocontrol agents prior to release.
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