Recolonization routes of intertidal species
Coalescent simulations showed that epifaunal species recolonized
disturbed intertidal habitats from northern source populations (Table
S3-S4). Specifically, for L. segnis , the best demographic model
was recolonization from the North (AIC weight = 0.72). In O .neglectus the most supported model showed the uplift lineage has
evolved through an admixture event between the Far and Nearby Northern
lineages (AIC weight = 0.51). For the host species, the results from
fastsimcoal simulations agreed with the previously published estimates
of recolonization using approximate Bayesian computation (Parviziet al. 2020). Durvillaea poha is inferred to have
recolonized the uplifted coasts via admixture between northern and
southern source populations (AIC weight = 1) while in D.
antarctica an admixture between the two northern source populations has
resulted in the evolution of the uplift lineage (AIC weight = 0.77). For
all four species, the recolonization events are estimated to have
occurred approximately 900 years ago, in line with carbon-dating
estimates of Akatore Fault rupture (Table S5).
Hierarchical-codemographic modelling using Multi-DICE supported a
concerted post-earthquake recolonization (τ mode = 953 y BP; τ mean =
791 y BP; τ median = 825 y BP) with support for all intertidal and
epibiotic species co-expanding within a 50 year period (Fig. 3). A more
relaxed co-expansion threshold of 200 years also supported synchronous
expansion of all four species which was estimated to have occurred 913 y
BP (τ mode = 913 y BP; τ mean = 736 y BP; τ median = 747 y BP; Fig.
S9-S10).