Rapid evolution or preadaptation in invasive Jacobaea vulgaris

Abstract

Native and invasive individuals of

Jacobaea vulgaris differ from each other in a number of traits related

to defence and growth. Two separate studies with different genetic

markers and partly also with different individuals both reveal that the most likely scenario of invasive J. vulgaris individuals is that they originated from multiple source populations. The chance of preadaptation is very little because it is very unlikely that all these different source populations al contained individuals that were already adapted to the new environment. The introduction of different source populations and the admixture of individuals from different populations have likely contributed to the fast evolution of J. vulgaris. Admixture increased the genetic variation and has also lead to recombination of native individuals that were isolated from each other in the native area.. The invasive character of Jacobaea vulgaris is especially expressed by the lower root- shoot ratio. With this change the competition with local species is increased. Bigger shoots leads to a higher photosynthetic capacity and more growth. Besides, within J. vulgaris plant size is positively correlated with the amount of seeds produced. As a result of this, spread and abundance of J. vulgaris easily increases.