Divergent lineages in a semi?arid mallee species, Eucalyptus behriana, correspond to a major geographic break in southeastern Australia

ABSTRACT: Abstract

Aim

To infer relationships between populations of the semi?arid, mallee eucalypt, Eucalyptus behriana, to build hypotheses regarding evolution of major disjunctions in the species' distribution and to expand understanding of the biogeographical history of southeastern Australia.

Location

Southeastern Australia.

Taxon

Eucalyptus behriana (Myrtaceae, Angiospermae).

Methods

We developed a large dataset of anonymous genomic loci for 97 samples from 11 populations of E. behriana using double digest restriction site?associated DNA sequencing (ddRAD?seq), to determine genetic relationships between the populations. These relationships, along with species distribution models, were used to construct hypotheses regarding environmental processes that have driven fragmentation of the species’ distribution.

Results

Greatest genetic divergence was between populations on either side of the Lower Murray Basin. Populations west of the Basin showed greater genetic divergence between one another than the eastern populations. The most genetically distinct population in the east (Long Forest) was separated from others by the Great Dividing Range. A close relationship was found between the outlying northernmost population (near West Wyalong) and those in the Victorian Goldfields despite a large disjunction between them.

Conclusions

Patterns of genetic variation are consistent with a history of vicariant differentiation of disjunct populations. We infer that an early disjunction to develop in the species distribution was that across the Lower Murray Basin, an important biogeographical barrier separating many dry sclerophyll plant taxa in southeastern Australia. Additionally, our results suggest that the western populations fragmented earlier than the eastern ones. Fragmentation, both west and east of the Murray Basin, is likely tied to climatic changes associated with glacial?interglacial cycles although it remains possible that major geological events including uplift of the Mount Lofty Ranges and basalt flows in the Newer Volcanics Province also played a role. In this study, we investigate the phylogeography and biogeographic history of the southeast Australian mallee eucalypt, Eucalyptus behriana, which has a distribution divided by several major biogeographical barriers. By reconstructing the relationships between isolated populations and building species distribution models to investigate potential environmental factors influencing the species distribution, we build hypotheses regarding how the species scattered distribution comes about. Both climatic and edaphic changes are shown to likely have influenced the species distribution, with current isolated populations representing refugia where the species has survived as intervening populations have become extinct.

SUBMITTER: Fahey P 

PROVIDER: S-EPMC7790638 | biostudies-literature | 2020 Dec

REPOSITORIES: biostudies-literature