COS 114-4 - Restoration genomics: Determining optimal scales for restoration management with a case study from eucalyptus

Abstract: Increased frequency and severity of extreme climate events (e.g., drought, bushfires) and ongoing habitat loss and fragmentation are increasing the need for restoration. A critical task land managers are faced with is determining appropriate genetic and geographic scales for species management. Genetic data has served as a key tool for delineating evolutionarily significant units (ESUs), yet the scale of differentiation can vary vastly depending on the type of genetic data utilized (e.g., neutral vs adaptive) and the scale of natural selection operating on ecologically important functional traits. Here we investigated the scale of local adaptation for drought and frost tolerance in two closely related, co-occurring eucalyptus species, using a landscape genomic approach, experimental drought manipulations, and a common garden study. We found that neutral IBD among sampling locations only became significant at distances >500km; in contrast, functional trait divergence typically operated on a much finer scale (i.e., 10s of km). Drought response strategies were largely divergent across these sympatric sister species. In many cases, the same trait was driven by different climatic selection pressures; species also exhibited opposing response functions to the same environmental variable. We further observed that trait heritability was 1.5-7X greater under well-watered conditions, thus stress reduced phenotypic variability, and the scale of geographic differentiation for the same functional trait was often greater when measured under high stress compared to well-watered conditions. Our findings highlight that the optimal scale selected for restoration management is marker-, trait-, and environment-dependent. Identifying the scale of geographic turnover for key limiting factors (e.g., drought and frost tolerance) is critical for improving selection of climate-adapted restoration stock and building greater resilience into ongoing forest fire recovery efforts.