Non-native seeds of Solidago gigantea perform equally well or weaker than native seeds during germination and early seedling growth

Abstract

Germination and early seedling establishment are critical bottlenecks in a plant’s life cycle and can strongly influence adult performance. While many studies showed that performance of adult plants can differ substantially between native and non-native populations, it remains unclear whether such differences are already evident during the earliest life stages. We compared germination success and early seedling growth of Solidago gigantea sourced from 28 native and 33 non-native populations. As adult plants from the non-native range typically grow much larger than their native counterparts, range-dependent eco-evolutionary dynamics likely contribute to the invasion success of this species. Seeds from native populations germinated equally well or better than those from non-native populations. Similar patterns were observed for seedling growth. Moreover, plants from plain habitats outperformed those from mountainous habitats, but this difference was only apparent within the non-native range. Other habitat variables showed no effect on germination or seedling performance. Although previous work indicates strong selection for increased growth rates in adult S. gigantea individuals from the non-native range, such selection seems not to act on germination or seedling establishment. Our findings imply that recruitment traits are probably not key targets of selection in the context of habitat differentiation or invasion dynamics.