Uplift-associated population structure
PCAs and neighbor joining trees revealed populations in the uplift zone
form genetically distinct clusters in both L. segnis and O.
neglectus . These findings were further confirmed by sNMF results where
the K with the lowest cross entropy value (K = 4) revealed
spatial structuring closely associated with the Akatore uplift zone for
both species. In the amphipod P. karaka , by contrast, virtually
no population structure was detectable along the relevant coastlines
(Fig. 2; Fig. S1-S3). Overall, the strong uplift-associated genetic
structure in strictly intertidal epifaunal species (L. segnis andO. neglectus ) closely matches that of their intertidal macroalgal
hosts (D. antarctica and D. poha ; Fig. 2; Fig. S1-S6). In
all four of these strictly intertidal species, a shallow yet distinct
genetic cluster is tightly linked to the Akatore Fault boundaries (from
Taieri Island in the north to Toko Mouth in the south; Fig. 1).
Additionally, in both intertidal hosts and their epifauna, genetic
admixture is detectable only at the fringes of the uplifted region (Fig.
2).