Protecting YEWth: ancient and veteran yew trees as collections of genetic diversity through centuries

Defining baselines of genetic diversity is crucial to understand how genetic diversity has decreased in response to recent environmental changes, but baselines are seldom available. Ancient and veteran trees offer a unique opportunity for describing baseline levels of genetic diversity in a species, because their DNA predates the population declines that have affected species in more recent times. The English yew Taxus baccata L., is one of the most long-lived species in Britain, with ancient and veteran trees occurring in and outside woodlands. Habitat fragmentation throughout the native range of T. baccata has caused population declines, and the consequent loss of genetic diversity will likely have an impact on future population resilience. To understand how much genetic diversity has been lost in T. baccata, the PhD student will: (1) analyse differences in genetic diversity by age group in woodland populations, to understand whether low regeneration in woodlands is associated with lower genetic diversity in young trees; (2) analyse genetic differentiation between trees outside woodlands (TOWs), including ancient and veteran trees planted in churchyards, and trees in woodlands, to understand whether TOWs have tempered the isolation of native woodlands by contributing to gene flow; (3) describe genomic diversity in ancient and veteran trees, to define baseline levels of genetic diversity for the species, and compare this baseline with genome-wide diversity in younger trees.