Genomic Screening Reveals That the Endangered <i>Eucalyptus paludicola</i> (Myrtaceae) Is a Hybrid

• Main Authors: Kor-jent van Dijk, Michelle Waycott, Joe Quarmby, Doug Bickerton, Andrew H. Thornhill, Hugh Cross, Edward Biffin
• Format: Article
• Language: English
• Published: MDPI AG 2020-12-01
• Series: Diversity
• Subjects: conservation; natural hybridisation; <i>Eucalyptus</i>; high throughput sequencing; NGS; South Australia
• Online Access: https://www.mdpi.com/1424-2818/12/12/468

A hybrid origin for a conservation listed taxon will influence its status and management options. Here, we investigate the genetic origins of a nationally endangered listed taxon—<i>Eucalyptus paludicola</i>—a tree that is restricted to the Fleurieu Peninsula and Kangaroo Island of South Australia. Since its description in 1995, there have been suggestions that this taxon may potentially be a stable hybrid species<i>.</i> Using a high throughput sequencing approach, we developed a panel of polymorphic loci that were screened across <i>E. paludicola </i>and its putative parental species <i>E. cosmophylla </i>and <i>E. ovata. </i>Bayesian clustering of the genotype data identified separate groups comprising <i>E. ovata </i>and <i>E. cosmophylla </i>while <i>E. paludicola </i>individuals were admixed between these two, consistent with a hybrid origin. Hybrid class assignment tests indicate that the majority of <i>E. paludicola </i>individuals (~70%) are F₁ hybrids with a low incidence of backcrossing<i>. </i>Most of the post-F₁hybrids were associated with revegetation sites suggesting they may be maladapted and rarely reach maturity under natural conditions. These data support the hypothesis that <i>E. paludicola </i>is a transient hybrid entity rather than a distinct hybrid species. We briefly discuss the conservation implications of our findings.