Evolutionary processes in an undescribed eucalypt: implications for the translocation of a critically endangered species

Abstract Background and Aims Knowledge of the evolutionary processes responsible for the distribution of threatened and highly localised species is important for their conservation. Population genomics can provide insights into evolutionary processes to inform management practices, including the translocation of threatened plant species. In this study, we focus on a critically endangered eucalypt, Eucalyptus sp. Cattai, which is restricted to a 40 km 2 area of Sydney, Australia and is threatened by increased urbanisation. Eucalyptus sp. Cattai is yet to be formally described in part due to its suspected hybrid origin. Here, we examined evolutionary processes and species boundaries in E. sp. Cattai to determine whether translocation was warranted. Methods We used genome-wide scans to investigate the evolutionary relationships of E. sp. Cattai with related species, and to assess levels of genetic health and admixture. Morphological trait and genomic data were obtained from seedlings of E. sp. Cattai propagated in a common garden to assess their genetic provenance and hybrid status. Key Results All analyses revealed that E. sp. Cattai was strongly supported as a distinct species. Genetic diversity varied across populations, and clonality was unexpectedly high. Interspecific hybridisation was detected, and was more prevalent in seedlings compared to in situ adult plants, indicating that post-zygotic barriers may restrict the establishment of hybrids. Conclusions Multiple evolutionary processes (e.g., hybridisation and clonality) can operate within the one rare and restricted species. Insights regarding evolutionary processes from our study were used to assist with the translocation of genetically ‘pure’ and healthy ex situ seedlings to nearby suitable habitat. Our findings demonstrate that it is vital to provide an understanding of evolutionary relationships and processes with an examination of population genomics in the design and implementation of an effective translocation strategy.