Biogeography of Australian Camphorosmeae and diversification in climatic
space and across arid habitat types
Abstract
This study investigates the biogeography of the Australian Camphorosmeae
(Amaranthaceae s.l.) and how it relates to shifts in climatic
niche and habitat types of the lineage. Building on previous research
and data resources, we integrate molecular phylogenetics, bioclimatic
data and biogeographic models to deepen our understanding of the
diversification and adaptation of this group across Australia’s diverse
landscapes in relation to palaeoclimatic changes. For 159 species
representing 12 genera, georeferenced distribution points were used to
define the most informative bioclimatic variables using principal
component analyses. Evolutionary shifts in climatic niches and habitat
types were analysed, revealing clade-specific shifts and adaptations to
different habitats and climatic conditions. Biogeographic analyses
allowed us to infer ancestral areas of Camphorosmeae in Australia and
relate their expansion over evolutionary time to habitat shifts. Key
periods of aridification in Australia, particularly during the Late
Miocene to Pliocene, and the already existing adaptation of this group
to warm and dry habitats, were critical in driving its diversification
through migration and local adaptation to varied habitats of arid
Australia. Our analyses suggest that the “Riverine Desert” habitat
that existed already in the Late Miocene and “migrated” eastwards
offered suitable conditions for ancestral Australian Camphorosmeae and
facilitated their early widespread occurrence in the Western and Eastern
Desert. We hypothesise that early diverging lineages such as Roycea
adapted to the later emerging “Desert Lake” habitat when it spread in
Western Australia during the Early Pliocene. Further habitat type shifts
occurred from “Riverine Desert” to “Shield Plain”, “Karst Plain”
and to “Sand Desert” also during the Pliocene and Pleistocene once
these habitat types emerged. This research shows the complex interplay
between ecological flexibility and niche conservatism in shaping the
biodiversity of Australian Camphorosmeae.