Population Genomics of Eucalypts

Eucalypts are of great ecological and economic importance. They dominate many woodland and forest landscapes in Australia and are planted in temperate to tropical areas worldwide for forestry. Population genomics research in eucalypts builds on a long history of genetics research, from quantitative trait analysis of field provenance trials to modern molecular genetics studies exploring neutral variation and population structure. It is backed by a high-quality reference genome and, whilst this rapidly expanding field is still in its infancy, it is already providing new insights into both ecological and industry-focused applications. This chapter reviews population genomics research in eucalypts, in the context of past genetics research. After describing the genomic resources available for eucalypts, we show that genomics is enabling greater resolution than ever before of species boundaries and patterns of hybridisation. Landscape genomics studies have revealed various patterns of population structure in natural populations, cryptic lineages within species and low divergence between closely related species. Genomic signatures of adaptation have been identified in several species, highlighting both climatic and edaphic factors as potential drivers of adaptation. In investigating the genetic architecture underlying complex traits, genomic tools are revealing not only associations with genes but also associations with differences in gene expression. With their worldwide importance, eucalypts are at the forefront of developments for integrating genomics into models for the genetic evaluation of forest tree breeding populations. Into the future, an increasing number of population genomics studies of eucalypts will help develop our understanding of the evolution of the genus; how species adapted to varied and changing environments; and the genetic architecture underlying adaptation and complex traits. Such knowledge will help guide species and provenance choices for conservation and ecological restoration under environmental change and will provide a valuable resource to breeding for forestry.