Variation in radial growth sensitivity to drought among genetic groups of common yew (Taxus baccata L.) in central Italy

Abstract

Common yew (Taxus baccata L.) is a long-living European species, with significant ecological importance. Climate change and severe droughts threaten its growth, emphasizing the need for preserving genetic diversity. By combining dendroecology and genetics, we aimed to identify groups of trees most resilient to changing climatic conditions. We analysed radial growth trends from 1951 to 2018 in three populations located in two mountain areas of central Italy with different rainfall regimes. From 298 selected yew trees, needles were collected for DNA extraction, and tree-ring cores were obtained for dendrochronological analysis. We assessed the relationship between tree growth and drought using the Standardized Precipitation Evapotranspiration Index (SPEI). The studied populations clustered in two distinct genetic groups, corresponding to the driest and wettest areas. At the rainiest site, in the period 1951–2018 yew growth was less constrained by evapotranspiration rates than at the driest area, but climate-growth analysis on moving windows indicates an increasing impact of drought. Growth recovery time after the 2003 drought was longer in individuals at the rainiest area compared to the more xeric sites. The yew trees of the driest area, which were further subdivided in two genetically distinct but spatially intermingled sub-groups, appeared to be better adapted to drought events and therefore more suitable for future warmer scenarios. This study highlights the climate sensitivity of common yew, showing that summer droughts can limit growth, and suggests the advantages of using a dendrogenetic approach to delve deeper into ecophysiological responses to be exploited for reforestation and conservation efforts.