Jacobaea vulgaris, Gaertn., Gaertn.

Jung, Stefanie, Lauter, Jan, Hartung, Nicole M., These, Anja, Hamscher, Gerd & Wissemann, Volker, 2020, Genetic and chemical diversity of the toxic herb Jacobaea vulgaris Gaertn. (syn. Senecio jacobaea L.) in Northern Germany, Phytochemistry (112235) 172, pp. 1-9 : 4

2.2. Genetic profile of J. vulgaris

Our results generated with AFLP markers draw the same picture as our former results using ISSR markers ( Jung et al., 2017). In total, three primer combinations produced 243 loci for 75 individuals of which 241 (99.2%) were polymorphic, hence show differences between individuals. AMOVA shows that the main part of the total genetic differentiation (96%) is located within populations while 4% of the genetic differentiation is among populations ( Table 3 ).

The principal co-ordinate analysis (PCoA) was performed to visualize genetic similarities. It shows scattered individuals along with any clustering ( Fig. 5 ). Coordinate 1 explains 29% of the variability and coordinate 2 explains 10%. As we do not see any grouping of individuals belonging to one population, PCoA results confirm AMOVA results and show that there is not too much differentiation among populations.

Genetic structure of J. vulgaris populations in its native and invasive region has been investigated before ( Doorduin et al., 2010). This study shows higher differentiation between populations (13.26%) in its native region which might be explained by the much greater distances between the different populations used in that study. The low differentiation we found in our study indicates that the J. vulgaris populations are somehow cross-linked to each other, leading to the conclusion that J. vulgaris forms a panmictic metapopulation in Northern Germany. This could be explained by long distance achene dispersion (e.g. via wind or hay transport) and a connection between populations via pollinators. At least 36 species are known to pollinate J. vulgaris , mainly Diptera like Syrphidae and Hymenoptera ( Vanparys et al., 2008). Therefore, the distances pollinating insects are able to overcome are very various. In human modified landscape for example insects can spread pollen up to 400 m ( Rader et al., 2011). In addition, J. vulgaris seeds are dispersed by wind, water and human activity ( Harper and Wood, 1957). Especially rail- and motorways seem to be good propagation vectors for seeds from J. vulgaris ( Harper and Wood, 1957) . For the related species Senecio inaequidens DC. studies have already shown the importance of rail- and motorways as dispersion way (Blanchet et al., 2015; Griese, 1996). In addition, the comparison between the genetic distance and the geographical distance (Mantel test) showed a small positive correlation which was not significant (r = 0.083, p = 0.08), hence we could not detect any isolation by distance, confirming the conclusion that J. vulgaris forms a metapopulation in Northern Germany.

Genetic diversity values range between 0.31 ± 0.01 (Neustadt) and 0.4 ± 0.07 (Rauischholzhausen). The average assumption is 0.35 ( Table 4 ). This is a high to moderate genetic diversity on average and fits to the results of other common Asteraceae with similar life traits. Mandák et al. (2009) investigated Carduus acanthoides L. in its native range using allozymes. C. acanthoides also shows high levels of genetic diversity and small genetic differentiation. Both species, J. vulgaris and C. acanthoides , are invasive in several parts of the world ( Desrochers et al., 1988; Doorduin et al., 2010). This also applies to Centaurea scabiosa L. in Denmark ( Ehlers, 1999). In this case a connection between genetic variation and population reproductive success could be detected. According to the same probability to disperse seeds via wind and the general positive correlation between genetic variation and fitness ( Leimu et al., 2006) we believe that this is also true for J. vulgaris . This would mean, that J. vulgaris has a great potential of spreading further und thus would aggravate the problem of toxic herbs on grazing fields of livestock. We interpret the overall genetic diversity in J. vulgaris , lacking specific differentiated genotypes to be the result of a panmictic metapopulation with no directing selection on the geographic range of our study.

Figures

Fig. 5. Principal co-ordinate analysis (PCoA) ordination of the genetic similarity of 75 individuals of J. vulgaris from Northern Germany. Coordinate 1 explains 29.47% of the shown variability and coordinate 2 explains 10.00% of the shown variability. Colours indicate membership to the different populations.