No inbreeding avoidance by female burying beetles regardless of whether they encounter males sequentially or simultaneously

Inbreeding avoidance reduces the probability that an individual will mate
with a related partner, thereby lowering the risk that it produces inbred
offspring suffering from inbreeding depression. Inbreeding avoidance can
occur through several mechanisms, including active mate choice, polyandry
and sex-biased dispersal. Here, we focus on the role of active mate
choice as a mechanism for inbreeding avoidance. Recent evidence suggests
that the experimental design used in mate choice experiments (i.e.
simultaneous versus sequential choice) can have a strong impact on the
strength of the reported mating preferences. In this study, we examine
whether similar effects of experimental design also apply in the context of
inbreeding avoidance. To this end, we designed two experiments on the
burying beetle Nicrophorus vespilloides that matched two different contexts
under which females encounter potential mates in the wild; that is, when
females encounter males simultaneously and sequentially. We found that
females were as likely to mate with related and unrelated males regardless
of whether they encountered male partners simultaneously or sequentially.
Thus, our study provides no evidence for inbreeding avoidance in
this species, and suggests that the number of mates present did not influence
the degree of inbreeding avoidance. We discuss potential explanations
for the lack of inbreeding avoidance through mate choice, including
lack of mechanisms for recognizing close relatives, low costs and/or low
risks of inbreeding and the presence of other inbreeding avoidance mechanisms,
such as sex-biased dispersal and polyandry coupled with post-copulatory
mate choice.