Influences of carrier sex, body size, and time on the symbiotic interaction between Nicrophorus vespilloides and the Uroobovella nova mite species complex.

Phoretic dispersal is critical in low-mobile invertebrates because it enables feeding, breeding, and gene flow. Phoresy may have serious evolutionary consequences for species in highly specific interactions. Mites within the Uroobovella nova species complex have a narrow range of carriers limited to burying beetles. Nicrophorus vespilloides, a model organism used in behavioural studies, is a common carrier of U. nova, but this interaction remains underexplored. This study investigated how carrier sex, body size, season, and year affect the relationship between U. nova and N. vespilloides. We tested the hypotheses that mite infestation is sex-biased because of differences in parental care between females and males and that larger individuals carry more mites. Mite prevalence was affected only by season. A slightly higher mite load was found in females than in males, and mites showed a significant but weak preference for beetle body size. Considerable temporal differences in mite load were found. Deutonymphs were highly specific when selecting attachment sites, irrespective of the carrier sex, and appeared on some body parts when the preferred sites had already been infested. The low specificity of U. nova towards N. vespilloides individuals and the high selectivity of attachment sites seem to increase the probability of colonising beetle brood chambers.