Phylogenetic Reconstruction of the Rainforest Lineage Fontainea Heckel (Euphorbiaceae) Based on Chloroplast DNA Sequences and Reduced-Representation SNP Markers

Abstract

Fontainea is a plant genus with nine recognised species that occur across the tropical and subtropical rainforests of Australia, Papua New Guinea, New Caledonia, and Vanuatu. One of these species is cultivated commercially as the source of a cancer therapeutic, and several other species are under threat of extinction. Despite this, the phylogenetic relationships of the genus have not been explored. Our study assessed the phylogeny of seven Fontainea taxa from the Australian and Pacific Island complex using chloroplast DNA sequence data and reduced-representation genome sequencing. Maximum-likelihood and consensus network trees were used to infer the topology of phylogenetic relationships between species, which highlighted three distinct lineages and a number of sister species. Our results indicated that the geographically disjunct species Fontainea venosa and F. pancheri formed a sister group at the earliest position of divergence for the genus. The data also revealed that the vulnerable Fontainea australis and the critically endangered F. oraria form a sister subclade with evidence of some shared plastid genotypes. Generally, our phylogenetic reconstruction supports the modern taxonomical nomenclature. However, we suggest further accessions across several species may support improved genetic distinctions between the sister groups of Fontainea within the genus.

The geno-geo-climate nexus: contributions of geographic and ecological factors in shaping the genomic divergence of two closely related threatened rainforest species of Fontainea Heckel (Euphorbiaceae)

“…Here, we focussed our analyses on the two closely related sister species (Brunton et al, 2022) Southern Fontainea (Fig. 1a) and Coastal Fontainea (Fig.…”

“…Fontainea Heckel (Euphorbiaceae) is a genus of dioecious rainforest shrubs and small trees with links to the Gondwana landmass (Brunton et al, 2023) that is patchily distributed among rainforest fragments of Australia, Papua New Guinea, New Caledonia, and Vanuatu. Several Fontainea species have low to moderate genetic diversity and occupy restricted environments as a result of historic rainforest contraction and expansion cycles, coupled with more contemporary effects of habitat loss, modi cation and fragmentation from human disturbance (Lamont et al, 2016, Brunton et al, 2022. The critically endangered F. oraria (Coastal Fontainea) and Vulnerable F. australis (Southern Fontainea) belong to a closely related, subclade that occurs across the heterogeneous landscape of the Wollumbin Caldera in central, eastern Australia (Act, 1999, Brunton et al, 2022.…”

“…Several Fontainea species have low to moderate genetic diversity and occupy restricted environments as a result of historic rainforest contraction and expansion cycles, coupled with more contemporary effects of habitat loss, modi cation and fragmentation from human disturbance (Lamont et al, 2016, Brunton et al, 2022. The critically endangered F. oraria (Coastal Fontainea) and Vulnerable F. australis (Southern Fontainea) belong to a closely related, subclade that occurs across the heterogeneous landscape of the Wollumbin Caldera in central, eastern Australia (Act, 1999, Brunton et al, 2022. Rossetto et al (2000) and more recently, Brunton et al (2022) showed that Southern Fontainea and Coastal Fontainea have shared plastid genotypes and that morphological differences between species may represent the in uence of distribution across the highly variable environment of the Wollumbin Caldera.…”

“…The critically endangered F. oraria (Coastal Fontainea) and Vulnerable F. australis (Southern Fontainea) belong to a closely related, subclade that occurs across the heterogeneous landscape of the Wollumbin Caldera in central, eastern Australia (Act, 1999, Brunton et al, 2022. Rossetto et al (2000) and more recently, Brunton et al (2022) showed that Southern Fontainea and Coastal Fontainea have shared plastid genotypes and that morphological differences between species may represent the in uence of distribution across the highly variable environment of the Wollumbin Caldera. Another hypothesis is that the two species are at various points along a speciation continuum as a result of geographic isolation and differing environments (Brunton et al 2022).…”

“…Rossetto et al (2000) and more recently, Brunton et al (2022) showed that Southern Fontainea and Coastal Fontainea have shared plastid genotypes and that morphological differences between species may represent the in uence of distribution across the highly variable environment of the Wollumbin Caldera. Another hypothesis is that the two species are at various points along a speciation continuum as a result of geographic isolation and differing environments (Brunton et al 2022).…”