Data from: Australian spiny mountain crayfish and their temnocephalan ectosymbionts: an ancient association on the edge of coextinction?

Australian spiny mountain crayfish (Euastacus, Parastacidae) and their
ecotosymbiotic temnocephalan flatworms (Temnocephalida, Platyhelminthes)
may have co-occurred and interacted through deep time, during a period of
major environmental change. Therefore, reconstructing the history of their
association is of evolutionary, ecological, and conservation significance.
Here, time-calibrated Bayesian phylogenies of Euastacus species and their
temnocephalans (Temnohaswellia and Temnosewellia) indicate
near-synchronous diversifications from the Cretaceous. Statistically
significant cophylogeny correlations between associated clades suggest
linked evolutionary histories. However, there is a stronger signal of
codivergence and greater host specificity in Temnosewellia, which
co-occurs with Euastacus across its range. Phylogeography and analyses of
evolutionary distinctiveness (ED) suggest that regional differences in the
impact of climate warming and drying had major effects both on crayfish
and associated temnocephalans. In particular, Euastacus and Temnosewellia
show strong latitudinal gradients in ED and, conversely, in geographical
range size, with the most distinctive, northern lineages facing the
greatest risk of extinction. Therefore, environmental change has, in some
cases, strengthened ecological and evolutionary associations, leaving
host-specific temnocephalans vulnerable to coextinction with endangered
hosts. Consequently, the extinction of all Euastacus species currently
endangered (75%) predicts coextinction of approximately 60% of the studied
temnocephalans, with greatest loss of the most evolutionarily distinctive
lineages.