Needle in a haystack: Holocene history of European larch in Central Europe revisited

Societal Impact Statement Defining nativity of species is crucial for their management. However, this is a complex task, especially for species that have been used and spread by humans for a long time. We combined paleoecological records with extensive genetic data to investigate the Holocene history of European larch—a common and economically important tree species in Central Europe. We found that larch persisted in small populations throughout the Holocene beyond its traditionally assumed native range but that many populations were later genetically replaced through human‐mediated translocations. Conservation and forestry policies regarding larch are already being revised based on our results. Summary European larch ( Larix decidua ) is a common tree species across Central Europe, but its postglacial range dynamics remain largely unexplored. As a consequence, larch is considered non‐native in a portion of its current distribution range. However, this status is based on traditional biogeographic narratives, rather than data‐based evidence. Here, we challenge these classical narratives by compiling comprehensive paleoecological evidence (pollen and phytoliths) of larch survival throughout the Holocene, together with an extensive microsatellite‐based survey of extant larch populations in Central Europe. We show that larch has survived the warm phases of the Holocene in fluctuating small populations across both lowland and montane Central Europe, possibly supported by human impact through the opening of closed‐canopy forests. However, most of the Holocene refugial lowland populations were genetically replaced by artificial translocations of individuals from the Alps over the last ca. 300 years. Our results demonstrate the complex dynamics of an economically important tree species in a landscape with long‐term human presence, such as Central Europe. On a practical level, we propose to focus the further discussion about the nativity status of larch on its genetic provenance, rather than presence per se.