Phenological Variation in Ambrosia artemisiifolia L. Facilitates Near Future Establishment at Northern Latitudes

Abstract

The invasive weed Ambrosia artemisiifolia (common ragweed) constitutes a great threat to public health and agriculture in large areas of the globe. Climate change, characterized by higher temperatures and prolonged vegetation periods, could increase the risk of establishment in northern Europe in the future. However, as the species is a short-day plant that requires long nights to induce bloom formation, it might still fail to produce mature seeds before the onset of winter in areas at northern latitudes characterized by short summer nights. To survey the genetic variation in flowering time and study the effect of latitudinal origin on this trait, a reciprocal common garden experiment, including eleven populations of A. artemisiifolia from Europe and North America, was conducted. The experiment was conducted both outside the range limit of the species, in Sweden and within its invaded range, in Croatia. Our main hypothesis was that the photoperiodic-thermal requirements of A. artemisiifolia constitute a barrier for reproduction at northern latitudes and, thus, halts the northern range shift despite expected climate change. Results revealed the presence of a north-south gradient in flowering time at both garden sites, indicating that certain European populations are pre-adapted to photoperiodic and thermal conditions at latitudes up to, at least, 60° N. This was confirmed by phenological recordings performed in a region close to the northern range limit, the north of Germany. Thus, we conclude that there exists a high risk for establishment and spread of A. artemisiifolia in FennoScandinavia in the near future. The range shift might occur independently of climate change, but would be accelerated by it.

Mechanistic species distribution modeling reveals a niche shift during invasion

“…, Scalone et al. ), since it is a quantitative short day plant requiring long nights to flower and set seed before lethal winter frosts (Essl et al. ).…”

“…Based on newly published common garden experiment data (Scalone et al. ), we were able to represent between‐population variation in the thresholds for bud and female flower development in the model. To quantify this, we reanalyzed data in which ragweed plants were grown in Sweden (59.8° N 17.6° W, beyond the northern limit of the invaded distribution, 20 individuals per population) and Croatia (45.5° N 18.7° W, core of the invaded distribution, 10 individuals per population; see Fig.…”

“…To parameterize a phenology model for individual native and invasive populations, we reanalyzed data from a common garden phenology experiment carried out within and beyond the invaded range (Scalone et al. ). We then used this information in a phenology‐based mechanistic distribution model (Chapman et al.…”

“…Symbols locate the experimental populations and gardens (Scalone et al. ) used to parameterize our models.…”

Ragweed Pollen Allergy: Burden, Characteristics, and Management of an Imported Allergen Source in Europe

“…These two environmental factors are increasing due to climate change and urbanization. Prediction models indicate that ragweed will be widely spread and become domestic in large parts of Europe [3, 35, 36]. …”