Disturbance driven co-diversification of host and epibiota
Genomic analyses reveal that past habitat disturbance has strongly shaped contemporary patterns of genetic variation among populations of interacting intertidal taxa. In the current study, both intertidal seaweeds (D. antarctica and D. poha ) and their obligate epifauna (L. segnis and O. neglectus ) show abrupt shifts in genotype composition that are both spatially and temporally linked to historic tectonic disturbance. These multispecies signatures thus highlight community-wide effects of large-scale ecological disturbance. Indeed, direct observations from recent coastal uplift events in New Zealand and Chile have reported that vertical displacement of tidal zone causes widespread extinction of intertidal macroalgae, creating substantial new intertidal habitats for recolonization (Castilla 1988; Ortega et al. 2014; Clark et al. 2017; Schiel et al. 2019). Our genomic findings confirm an historic uplift-driven elimination of intertidal macroalgal communities, followed by rapid and parallel recolonization of empty intertidal habitats. These strong and concordant genomic signatures of historic disturbance persist to present because early-recolonizing lineages can reach high densities and subsequently exclude late-arriving individuals (Ibrahim et al.1996; Waters et al. 2013; De Meester et al. 2016), thus facilitating strong genetic differentiation between ancestral versus newly colonized areas (Excoffier et al. 2009).