Data from: The role of host phenology in determining the incidence of an insect sexually transmitted infection

Changes in the timing of life history events within the year alter the
degree to which the activity patterns of different species coincide,
making the dynamics of interspecific interactions sensitive to the
phenology of the interacting parties. For parasites, the availability of
suitable hosts to infect represents a crucial determinant of dynamics, and
changes in the host (and parasite) phenology may thus alter disease
epidemiology and the conditions for disease maintenance. We tested the
hypothesis that the incidence of a sexually transmitted mite infection,
Coccipolipus hippodamiae, in Adalia bipunctata ladybird beetles in Sweden
was determined by host phenology, namely presence/absence of sexual
contact between cohorts of the host. We observed that the pattern of mite
presence/absence across Swedish A. bipunctata populations was highly
reproducible between years, implying a persistent biological/ecological
basis underlying the incidence. Further, ladybirds from populations where
the mite was absent were able to acquire mites during copulation, develop
a mite infection, and transmit infection onward, indicating an ecological
(rather than biological) driver of mite incidence. Observations of
ladybird phenology in natural populations provided evidence of sexual
contact between overwintered and new cohort adults in populations where
the mite was present. In contrast, new cohort ladybirds in the two
northern Swedish populations where the mite was not present had not had
sexual contact with the overwintered generation, creating a ‘hard stop’ to
mite transmission. We conclude that variation in host phenology may be an
important driver of the incidence of sexually transmitted infections
(STIs) by determining the presence/absence of sexual contact between
generations. More generally, we hypothesize that sensitivity to variation
in host phenology will be highest for parasites like STIs that infect one
host species, one host life stage and are directly transmitted on contact
between host individuals.