Sea turtle symbiosis facilitates social monogamy in oceanic crabs via refuge size

Abstract

The capacity for resource monopolization by individuals often dictates the size and composition of animal groups, and ultimately, the adoption of mating strategies. For refuge-dwelling animals, the ability (or inability) of individuals to monopolize refuges should depend on the relative size of the refuge. In theory, groups should be larger and more inclusive when refuges are large, and smaller and more exclusive when refuges are small, regardless of refuge type. We test this prediction by comparing the size and composition of groups of oceanic crabs (Planes minutus) living on plastic flotsam and loggerhead sea turtles. We found that (i) surface area of refuges (barnacle colonies on flotsam and supracaudal space on turtles) is a better predictor of crab number than total surface area and (ii) flotsam and turtles with similar refuge surface area host a similar number (1-2) and composition (adult male-female pairs) of crabs. These results indicate that group size and composition of refuge-dwelling animals are modulated by refuge size and the capacity for refuge monopolization. Moreover, these results suggest that sea turtle symbiosis facilitates social monogamy in oceanic crabs, providing insights into how symbiosis can promote specific mating strategies.

Hitchhiking the high seas: Global genomics of rafting crabs

“…marinus. In the absence of any differences in the mitochondrial genome or at least at the COI locus-a fast-evolving locus often used as a species-level barcode (Evans & Paulay, 2012)-our interpretation of these results is that there has been a (Pfaller & Gil, 2016) or the same sea turtle (Frick et al, 2011) yet do not interbreed. Identifying the factors that both promote hybridization in specific areas and deter hybridization elsewhere would shed light on the mechanisms underlying the maintenance and merger of species diversity on a broader scale (Abbott et al, 2013;Barton, 2001).…”

“…marinus and Pl. minutus /major share the same raft (Pfaller & Gil, ) or the same sea turtle (Frick et al, ) yet do not interbreed. Identifying the factors that both promote hybridization in specific areas and deter hybridization elsewhere would shed light on the mechanisms underlying the maintenance and merger of species diversity on a broader scale (Abbott et al, ; Barton, ).…”