How do phoront density and anuran host traits affect phoresy?

Phoresy is likely a commensal interaction, in which a phoront attaches itself to the body of a host for dispersal. Host traits and environmental characteristics may determine phoresy patterns. We examined whether the density of microscopic phoronts on frogs living in the water between the leaves of bromeliads (phytotelma) was determined by the species, richness, size and abundance of anurans (frog hosts). We identified phoronts on the skin of three hylid species (Dendropsophus bromeliaceus, Phyllodytes luteolus, and Ololygon arduoa) associated to bromeliads at eight sites in the Atlantic Forest of Brazil. We report the first records of phoretic interaction between these bromeligenous frog hosts with the aquatic invertebrates of bromeliads e.g., Bdelloidea, Copepoda, Acari, and Ostracoda. The size of frog hosts had negative relationship with the abundance of phoronts. However, when the species were analyzed separately, the size of O. arduoa had positive relationship with the abundance of phoronts. The richness of anurans in bromeliads did not influence phoresy in any of the observed variables. Our results showed that host attributes, such as identity, size, and abundance, as well as the density of phoronts in their habitat, influenced the phoresy rates. This implies that not only host attributes, but also those of the phoront need to be considered in phoresy studies.