Using molecular and morphometric data as operational criteria for the analysis of a threatened rainforest species complex shows interspecific variation, with implications for cryptic-species delimitation and conservation

Aaron J. Brunton; Paul I. Forster; Steven M. Ogbourne; Maurizio Rossetto; David S. Schoeman; Gabriel C. Conroy

doi:10.1071/SB23024

RESEARCH ARTICLE (Open Access)

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Using molecular and morphometric data as operational criteria for the analysis of a threatened rainforest species complex shows interspecific variation, with implications for cryptic-species delimitation and conservation

Aaron J. Brunton

^A ^B ^* , Paul I. Forster ^C , Steven M. Ogbourne ^D , Maurizio Rossetto ^E , David S. Schoeman ^B ^F and Gabriel C. Conroy ^A ^B

+ Author Affiliations

- Author Affiliations

^A Centre for Bioinnovation, University of the Sunshine Coast, Maroochydore, Qld 4556, Australia.

^B School of Science and Engineering, University of the Sunshine Coast, Maroochydore, Qld 4556, Australia.

^C Department of Environment, Science & Innovation, Queensland Herbarium & Biodiversity Science, Brisbane Botanic Gardens, Toowong, Qld 4066, Australia.

^D QBiotics Group Ltd, Brisbane, Qld 4068, Australia.

^E Research Centre for Ecosystem Resilience, Royal Botanic Garden, Sydney, NSW 2000, Australia.

^F Department of Zoology, Centre for African Conservation Ecology, Nelson Mandela University, Gqeberha, 6001, South Africa.

^* Correspondence to: abrunton@usc.edu.au

Handling Editor: Jennifer Tate

Australian Systematic Botany 37, SB23024 https://doi.org/10.1071/SB23024

Submitted: 15 August 2023 Accepted: 4 March 2024 Published: 4 April 2024

© 2024 The Author(s) (or their employer(s)). Published by CSIRO Publishing. This is an open access article distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND)

Abstract

Resolution of systematic associations and species boundaries is vital for developing conservation priorities for threatened taxa. A complex of Fontainea (Euphorbiaceae) populations, endemic to rainforest communities in central-eastern Australia, comprises several taxonomically challenging species. Fontainea oraria is Critically Endangered, with only one natural population of 10 mature individuals, with the closely related species F. australis being listed as Vulnerable. A recently discovered Fontainea population (currently nominated as F. sp. Coffs Harbour) with taxonomic similarities to F. oraria has been provisionally listed as Critically Endangered, with fewer than 40 individuals. This study employed an integrative approach, combining genetic data and morphometrics to determine species boundaries for three threatened Fontainea population groups as a model system for an integrative approach to delimiting cryptic species. Although our results suggest the potential subdivision of the population groups into three taxa, caution is warranted because this hypothesis remains inconclusive. Taxonomic challenges demand a careful approach, acknowledging the possibility of alternative interpretations. Contrary to supporting distinct species, our morphological and genetic data may also be interpreted as indicative of a single species with geographic variation, a phenomenon observed in genetically linked populations experiencing isolation by distance. Overall, we highlight the need for further research to establish species limits to guide conservation actions.

Keywords: conservation genetics, digital morphometrics, genome-wide markers, geographic variation, non-destructive sampling, rare species, species delineation, taxonomic resolution.

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