Phenotypic variation of 38 European Ambrosia artemisiifolia populations measured in a common garden experiment

Abstract

The knowledge of phenotypic variation in the European range of the highly allergenic Ambrosia artemisiifolia L. (common ragweed) is not entirely complete, even though it is an invasive species of utmost concern. We hypothesized the prevalence of phenotypic differentiations between common ragweed populations in the introduced range, and we assumed that those differentiations were related to environmental conditions at the points of origin. Using a common garden experiment, we investigated biomass allocation, growth rates, and flowering phenology of 38 European common ragweed populations originating from a major geographical gradient. We observed considerable phenotypic variation in growth parameters and flowering phenology, e.g. mean aboveground biomass varied from 23.3 to 47.3 g between the populations. We were able to relate most measured traits with environmental parameters prevailing at the points of origin. For example, early growth of ruderal populations was highly correlated with temperature and precipitation at the point of origin. Late growth and flowering phenology were highly correlated with latitude, i.e. individuals from northern populations grew smaller and flowered and dispersed their pollen and seeds up to 5 weeks earlier than individuals from southern populations. We also found a longitudinal gradient in flowering phenology which has not yet been described. The existence of such a high variability in the introduced range may facilitate further range expansion. We suggest that the correlation with environmental variables rests upon genetic variation possibly due to adaptations to the respective environment. To clarify if such adaptation results from multiple events of introduction or as evolutionary response after introduction, genetic investigations are needed.

Phenological Variation in Ambrosia artemisiifolia L. Facilitates Near Future Establishment at Northern Latitudes

“…also in a potential invasion area. Phenological north-south gradients, similar to our findings, have been revealed earlier [16, 54, 55] in common ragweed. However, none of these studies were done at more than one common garden experiment site, and only at sites within the species´ range of distribution.…”

“…This emphasizes the need for more studies involving common garden experiments beyond the studied species´ range. Earlier reports show a negative correlation between maximum aboveground biomass and latitude [16], which indicates that there exists a trade-off between early flowering and plant height. However, here plant height was significantly affected by the common garden sites but not by the latitudinal origin of populations.…”

“…photoperiod, temperature and their interaction) is required, as has been observed in the short-day grass Microstegium vinimeum [13]. Several studies have reported earlier flowering in populations sampled at the northern range margins compared to the southerly counterparts [14–16]. …”

“…field, roadside, river-side and wasteland [41]. In addition, the presence of a north-south gradient in flowering time within introduced European populations from latitude 54° N to 44° N was recently shown in a common garden experiment located within the invaded area [16]. …”

Light-driven host-symbiont interactions under hosts’ range shifts caused by global warming: A review

“…This is of special importance in boreal and arctic ecosystems because of the predicted rapid changes in these areas (ACIA, 2005). Increased attention directed toward northern areas encompasses problems associated with invasion ecology and range shifts of species and their populations (Saikkonen et al, 2012;Taulavuori, 2013;Leiblein-Wild and Tackenberg, 2014). Light environment, and especially differences in the spectrum of light, as an ecological factor, however, has received little attention in this respect.…”