ddRAD of Hawaiian Ariamnes spiders

The diversification of a host organism can be influenced by both the
external environment and its assemblage of microbes. Here, we use a young
lineage of spiders, coupled with a chronologically arranged series of
volcanic mountains, to determine the evolutionary history of a host and
its associated microbial communities, altogether forming the “holobiont”.
Using the stick spider Ariamnes waikula (Araneae, Theridiidae) on the
island of Hawaiʻi, and outgroup taxa on older islands, we tested whether
the host spiders and their microbial constituents have responded in
similar ways to the dynamic abiotic environment of the volcanic
archipelago. The expectation was that each component of the holobiont (the
spider hosts, intracellular endosymbionts, and gut microbiota) should show
a similar pattern of sequential colonization from older to younger
volcanoes. In order to investigate this, we generated ddRAD data for the
host spiders and 16S rRNA gene amplicon data from their microbiota.
Results showed that the host A. waikula is strongly structured by
isolation, suggesting sequential colonization from older to younger
volcanoes. The endosymbiont communities were markedly different between
Ariamnes species on different islands, but more homogenized among A.
waikula populations. In contrast, the gut microbiota was largely conserved
across all populations and species, and probably mostly environmentally
derived.  Our results highlight the different evolutionary
trajectories of the distinct components of the holobiont, showing the
necessity of understanding the interplay between components in order to
assess any role of the microbial communities in host diversification.