First come, first served: arrival order shapes competitive outcomes among co-occurring alien plants
Year: 2026
Type: preprint
Abstract: Multiple alien plant species commonly co-occur in disturbed habitats, yet how arrival order shapes competition among them is largely untested. Previous work has examined priority effects between alien and native species, but the case in which co-occurring aliens compete with each other after arriving at different times has received little attention. We used a greenhouse experiment in Stuttgart, Germany, with nine annual alien species common to Central Europe, factorially manipulating neighbour identity and order of arrival, to test whether arriving first confers a competitive advantage among aliens and whether arriving second reduces establishment. Because pots were not thinned to single individuals, we used per-capita biomass to separate per-individual growth from density. Across all nine species, plants that arrived three weeks before their neighbour produced 41% more per-capita biomass than those arriving simultaneously, and we found no evidence that this advantage differed among species. Arriving second into already-occupied pots roughly halved the number of established individuals. Species also differed strongly in their competitive effect on neighbours, and this suppressive effect was closely correlated with species size, forming a size-structured competitive hierarchy. The priority advantage operated through increased per-capita growth rather than through higher establishment, whereas the cost of arriving second acted primarily on establishment. These results show that among co-occurring alien plants, arrival order confers a broad competitive advantage, and suggest that the timing of colonisation may be as important as species identity in determining which alien species gains an early competitive advantage in newly disturbed ground.
Source: Research Square
Language: English
Subfield: Nature and Landscape Conservation
Field: Environmental Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7225800025