Fine‐tuned ability to predict future competitive environment inAmbrosia artemisiifoliaseeds

Abstract

Summary Competition from native species is a key mechanism for biotic resistance to invasion. Accelerated germination to pre‐empt resources or delayed germination and induced dormancy until the next growing season are two alternative strategies for annual invasive plants to avoid the drawbacks of competition at the seed stage. In Ambrosia artemisiifolia, both of these tactics could theoretically increase its long‐term fitness. However, their relative importance has never been tested. We studied the germination pattern of A. artemisiifolia seeds in various competitive environments by experimentally modifying the life stage (seed, seedling, adult), density (low, high) and also the identity (intraspecific and 3 interspecific competitors) of neighbours in controlled conditions. When facing competition of seeds and seedlings at high densities or of particular identity, A. artemisiifolia accelerated its germination. In contrast, A. artemisiifolia followed a competition avoidance strategy in the presence of established adult heterospecific neighbours by delaying germination and reducing the germination fraction through induction of secondary dormancy. By testing the seedlings' performance in the same competition situations as those of seeds, we showed that the germination responses were beneficial in the case of heterospecific, but not of conspecific neighbours.

Explaining variability in the production of seed and allergenic pollen by invasive Ambrosia artemisiifolia across Europe

“…Since competition effects are important in the early developmental stages of A. artemisiifolia (Fenesi et al 2014), we started the study once most plants were expected to have established, but were still in an early vegetative stage (ca. June, but the exact date differed according to phenology at the specific site).…”

Effects of seed traits variation on seedling performance of the invasive weed, Ambrosia artemisiifolia L.

“…During this time, seedling performance is crucial and can have an impact on later life stages, and therefore affect the overall fitness of the parents (Gross, 1984;Renata D Wulff, 1986). The successful development of a seedling increases the chances for effective establishment of opportunist species or plant invaders in new areas (Fenesi et al, 2014;Sk alov a et al, 2012). It is therefore very important to understand what the factors are that can influence seedling performance.…”

“…artemisiifolia invasion in Europe is an especially interesting case study, as invasion success is known to be linked to seed characteristics (Fenesi et al, 2014;Fumanal et al, 2008;Guillemin and Chauvel, 2011). On top of being highly variable (Fumanal et al, 2007a;Gebben, 1965), the seeds are able to survive for many years in the soil (Bassett and Crompton, 1975), allowing the creation of a long-lasting soil seed bank.…”

The fitness benefits of germinating later than neighbors

“…For example, male parasitoid wasps that emerge from the host earlier in response to high wasp density have increased mating success (Moynihan and Shuker, ). Similarly, accelerated seed germination occurs in response to neighboring seeds, and this response increases individual fitness (Orrock and Christopher, ; Fenesi et al., ). But emergence is not always accelerated in response to neighbors.…”