Origins of the rare Australian daisy <i>Erigeron conyzoides</i> and its implications for biological control research and conservation management

Stephanie Chen; Alicia Grealy; Michelle Rafter; Ben Gooden; Alexander Schmidt-Lebuhn

Just Accepted

This article has been peer reviewed and accepted for publication. It is in production and has not been edited, so may differ from the final published form.

Origins of the rare Australian daisy Erigeron conyzoides and its implications for biological control research and conservation management

Stephanie Chen , Alicia Grealy, Michelle Rafter, Ben Gooden, Alexander Schmidt-Lebuhn

Abstract

Context Confidence in risk analyses for weed biological control (biocontrol) agents is underpinned by knowledge of the phylogenetic associations between the target weed and off-target plant species, with an emphasis on native taxa that co-occur with the weed in its introduced range. The origins of off-target plant species are also considered when assessing potential adverse effects of releasing weed biocontrol agents into the environment. Erigeron bonariensis L. (flaxleaf fleabane), native to South America, is a major cropping weed in North America, Europe, and Australia. Phylogenomic analysis of the weed’s tribe, Astereae, for a biocontrol program has put into question the existence of native Australian fleabanes. Aims We aimed to resolve the establishment means of a supposed native species to Australia by testing its phylogenetic and morphological associations with other Erigeron taxa at a global scale. Methods Target sequence capture data were combined with traditional taxonomy. Key results We rediscovered the closest presumed native relative of flaxleaf fleabane, the rare and declining E. conyzoides F.Muell. (daisy fleabane), during field work in Victoria, Australia. Molecular data and morphology indicated that E. conyzoides and E. acer L. from the northern hemisphere are not distinct. Conclusions Erigeron conyzoides is very likely not a distinct species endemic to Australia but rather a disjunct population of E. acer. Implications This finding improves confidence in the host-specificity of candidate biocontrol agents for fleabane in Australia, as we argue that the closest related truly native species is much more distantly related to fleabane than previously thought.

BT24047 Accepted 16 December 2024