Recruitment Traits Could Influence Species’ Geographical Range: A Case Study in the Genus Saxifraga L.

The reasons why species occur widespread and others have a narrow geographical range may be explained by habitat specialization or ecological niche breadth. For species in the genus Saxifraga, habitat specialization alone cannot explain the distributional differences observed, and neither do dispersal strategies. Thus, geographical range differences may be explained by differences in recruitment responses and levels of intraspecific variability.

We studied recruitment traits (i.e., germination, emergence, survival) in 25 Saxifraga from 79 populations from across the European Alps, using laboratory and common garden experiments. We found differences between the groups (widespread, narrow-ranged) in germination to temperature, with widespread species having a higher tolerance to warm temperatures. Furthermore, we found that cold conditions triggered germination better than warmer conditions, for both groups. This is an exception to the globally stated pattern of warm cues for germination previously found for alpine species. However, in five of six studied traits, widespread and narrow-ranged Saxifraga species behaved similarly. Considering intraspecific variability, widespread species had a broader variation in their emergence timing than narrow-ranged species. This was also reflected by a broader variation in mean annual temperatures of seed collection sites, pointing towards a strong link between climatic conditions and recruitment responses.

This study highlights that the overall contribution of seedling recruitment to distribution ranges is mainly driven by the earliest life-stage, that timing is key for adaptation and, that species of the genus Saxifraga have adapted their whole life cycle to cold conditions, which means a severe challenge for the genus in a warmer world.  


Science Flash Margreiter2

(A) Plant life cycle of Saxifraga bryoides, a perennial hemikryptophyte flowering multiple times. The early life stages cover transitions from seed to seedling and seedling to juvenile plant, which are key processes in population dynamics that can influence species abundances. (B) Saxifraga species from top left clockwise: S. bryoides, S. exarata, S. aizoides, S. rudolphiana.

Margreiter, V., Porro, F., Mondoni, A., and Erschbamer, B. (2022). Recruitment Traits Could Influence Species’ Geographical Range: A Case Study in the Genus Saxifraga (L.). Front. Plant Sci. 13:827330.

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