Protection Mutualists Affect Colonization And Establishment Of Host-Associated Species In A Coral Reef Cryptofauna Community

Protection mutualists display territorial behaviors, which also act as protective services for their host species. These territorial behaviors may inhibit the ability of other organisms to use the habitat provided by the host species. Coral guard crabs (Trapeziidae) and snapping shrimps (Alpheidae) form a guild of protection mutualists that aggressively defend their obligate host corals from predators. Here, we investigate how these protection mutualists affect the colonization and/or establishment of the community associated with the host coral. We found that Trapezia intermedia and Alpheus lottini both had species-specific effects on the probability of colonization. Alpheus lottini inhibited recruitment by conspecifics, but did not affect the settlement of Trapezia spp. T. intermedia did not affect recruitment by Trapezia spp. or Alpheus spp. Both T. intermedia and A. lottini limited colonization by some other decapod species, including xanthid and portunid crabs. The presence of protection mutualists affected the trajectory of communities associated with host corals such that the initial presence of protection mutualists explained 20% of variation in community composition six-months later. The communities on corals with protection mutualists had similar richness but lower beta-diversity than control corals after six months. Host response to protection mutualists was mixed. Over the two-month colonization study when the mutualist treatments were maintained and colonizing species were removed, host corals with both protection mutualists had lower growth rates than control corals or corals with only T. intermedia; however, coral growth did not differ between treatments over the six-month establishment study when community trajectories were followed without interference.