diversity Article Allele Surfing and Holocene Expansion of an Australian Fig (Ficus—Moraceae) Brendan C. Wilde 1,*, Susan Rutherford 2, Jia-Yee S. Yap 1 and Maurizio Rossetto 1 1 Research Centre for Ecosystem Resilience, Australian Institute of Botanical Science, The Royal Botanic Garden, Sydney 2000, Australia;
[email protected] (J.-Y.S.Y.);
[email protected] (M.R.) 2 Institute of Environment and Ecology, Academy of Environmental Health and Ecological Security, Jiangsu University, Zhenjiang 212013, China;
[email protected] * Correspondence:
[email protected] Abstract: The creek sandpaper fig of southeastern Australia, Ficus coronata Spin, is culturally sig- nificant to Australian traditional owners who made use of the leaves to smooth timber and ate the fruit. The species is thought to have a long history on the continent, with some suggesting a Gondwanan origin. However, distributional patterns and overall ecology suggest a recent expansion across suitable habitats. We used landscape genomic techniques and environmental niche modelling to reconstruct its history and explore whether the species underwent a recent and rapid expansion along the east coast of New South Wales. Genomic analysis of 178 specimens collected from 32 popu- lations throughout the species’ New South Wales distribution revealed a lack of genetic diversity and population structure. Some populations at the species’ southern and western range limits displayed unexpected diversity, which appears to be the result of allele surfing. Field work and genetic evidence suggest a Holocene expansion which may have increased since European colonisation. We also present a novel method for detecting allele surfing—MAHF (minor allele at highest frequency).