Germination performance of native and non-native Ulmus pumila populations.

HIRSCH, H.; WYPIOR, C.; VON WEHRDEN, H.; WESCHE, K.; RENISON, D.; HENSEN, I.

NeoBiota

Pensoft

Año: 2012 vol. 15 p. 53 - 68

1314-2488

Germination is a crucial step for invasive plants to extend their distribution under diferent environmental conditions in a new range. Terefore, information on germination characteristics of invasive plant species provides invaluable knowledge about the factors which might contribute to the invasion success. Moreover, intra-specifc comparisons under controlled conditions will show if diferent responses between non-native and native populations are caused by evolutionary changes or by phenotypic plasticity towards diferent environmental infuences. Tis paper focuses on the germination of native and non-native Ulmus pumila populations. We ex-pected that non-native populations would be characterized by their higher fnal germination percentage and enhanced germination rate, which might indicate an infuence due to corresponding climatic conditions. Germination experiments with a moderate and a warm temperature treatment did not reveal signif- cant diferences in fnal germination percentage. However, seeds from the North American non-native range germinated signifcantly faster than native seeds (p < 0.001). Additionally, mean time to germina- tion in both ranges was signifcantly negatively correlated with annual precipitation (p = 0.022). At the same time, this relationship is stronger in the native range whereas mean time to germination in non- native populations seems to be less infuenced by climatic conditions. Diferent germination responses of the North American populations could be caused by a fast evolutionary change mediating a higher tolerance to current climatic conditions in the non-native range. However, our fndings could also be caused by artifcial selection during the introduction process and extensive planting of U. pumila in its non-native range. Nevertheless, we assume that the faster germination rate of non-native populations is one potential explanation for the invasion success of U. pumila in its new range since it might provide a competitive advantage during colonization of new sites.