Colonize, radiate, decline: unraveling the dynamics of island community assembly with Fijian trap-jaw ants

The study of island community assembly has been fertile ground for developing and testing theoretical ideas in ecology and evolution.  The eco-evolutionary trajectory of lineages after colonization has been a particular interest, as this is a key component of understanding community assembly.  In this system, existing ideas such as the taxon cycle posit that lineages pass through a regular sequence of eco-evolutionary changes after colonization, with lineages shifting toward reduced dispersal ability, increased ecological specialization, and declines in abundance. However, these predictions have historically been difficult to test. Here, we integrate phylogenomics, population genomics, and x-ray microtomography/3D morphometrics, to test hypotheses for whether the ecomorphological diversity of trap-jaw ants (Strumigenys) in the Fijian archipelago is assembled primarily through colonization or post-colonization radiation, and whether species show ecological shifts toward niche specializat...