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The ecological opportunities associated with transitions across the
marine-freshwater interface are regarded as an important catalyst of
diversification in a range of aquatic taxa. Here, we examined the role of
these major habitat transitions and trophic diversification in a radiation
of Australasian fishes using a new molecular phylogeny incorporating 37
Terapontidae species. A combined mitochondrial and nuclear gene analysis
yielded a well supported tree with most nodes resolved. Ancestral
terapontids appear to have been euryhaline in habitat affiliation, with a
single transition to freshwater environments producing all Australasian
freshwater species. Mapping of terapontid feeding modes onto the molecular
phylogeny predicted carnivorous dietary habits were displayed by ancestral
terapontids, which subsequently diversified into a range of additional
carnivorous, omnivorous, herbivorous and detritivorous dietary modes upon
transition to freshwater habitats. Comparative analyses suggested that
following the freshwater invasion, the single freshwater clade has
exhibited an increased rate of diversification at almost three times the
background rate evident across the rest of the family. The
marine-freshwater transition within Terapontidae appears to have resulted
in substantial dietary radiation in freshwater environments, as well as
increased lineage diversification rates relative to euryhaline-marine
habitats.
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