Ecological attributes promoting intra-continental range-expansion of a native annual forb triggered by intensified land-use

Abstract

Intra-continental range-expansion of native species tracking human-induced environmental changes has become an important phenomenon, and recently has been suggested to be recognized as a distinct biogeographic category, namely neonative. However, it remains difficult to analyze how range-expansions are triggered by certain environmental changes and which biological and ecological species attributes are involved. We compared biological and ecological attributes and the performance in different test environments during the entire life cycle of a range-expanding neonative in Romania, Xeranthemum cylindraceum, with a congeneric resident native, X. annuum, through a series of controlled experiments. Both species proved to share several biological and ecological attributes, e.g. high potential for long-distance dispersal by multiple vectors, biochemical defense against herbivores by means of cyanogenic compounds, and surprisingly, they were found to have similar germination and performance niches throughout the range of climatic environments tested by us. Differences between the two species, a broader climatic and habitat niche, higher germination rate and viability of seeds can give explanation to the successful spread beyond the historical range of X. cylindraceum. However, based on shared biological attributes between the two species, which confer the potential to spread, and the considerably higher seed output found in the case of the resident native, X. annuum is equally prepared to expand its range. With changing climate and persisting human-induced disturbance, in this case intensive grazing by sheep, we may expect the spread of this species after passing the presumed migration lag phase.