Crayfish molting as a disturbance effect in the assembly of ectosymbiotic communities

• DOI: 10.1002/oik.11204
• Publication Date: 2025-05-20T11:29:18Z
• Authors: Philip McElmurray; Spencer S. Bell; Robert P. Creed; Bryan L. Brown

Recently, there has been an effort to view the study of symbiosis through the lens of community ecology. Hosts can be viewed as patches in a symbiont metacommunity, and host ontogenetic change can alter the properties of patches occupied by symbionts. We used a freshwater cleaning symbiosis between a population of Conhaway crayfish Cambarus appalachiensis and their community of ectosymbiotic branchiobdellidan worms to explore how an ontogenetic change in host molting can act as a disturbance in symbiont community assembly. Based on a year‐long survey of crayfish hosts and their symbiont communities, host molting acted as a disturbance that reset the process of symbiont community assembly. Crayfish that had recently molted had a symbiont community that was more similar to smaller crayfish. This dynamic is likely driven by a competition–colonization tradeoff between the species in the symbiont community, with smaller symbionts having better colonization ability, and larger symbionts having better competitive ability. The richness of the symbiont community was lowest on crayfish that molted very recently, supporting the idea that the symbiont communities on recently molted crayfish are composed of the early colonizing species that characterize the symbiont communities on smaller crayfish. On larger crayfish that had not molted recently, the richness of the symbiont community was higher, while it was highest on larger crayfish that had molted somewhat recently. This suggests that the disturbance caused by molting was interacting with competition–colonization tradeoffs among the symbionts to determine the composition of the ectosymbiotic community. Our results show that host‐related disturbances can be an important part of community assembly in symbiont communities, and ectosymbioses involving a molting invertebrate host provide a unique tool to study the processes underlying community assembly in symbiotic communities.