Abstract:
Sexually reproducing organisms face a strong selective pressure to find a mate
and ensure reproduction. An important criterion during mate-selection
is to avoid
closely related individuals and subsequent potential fitness costs of resulting inbred
offspring. Inbreeding avoidance can be active through kin recognition during mate
choice, or passive through differential male and female-biased
sex ratios, which effectively
prevents sib-mating.
In addition, sex allocation, or the resources allotted to
male and female offspring, can impact mating and reproductive success. Here, we
investigate mate choice, sex ratios, and sex allocation in dispersing reproductives
(alates) from colonies of the termite Cubitermes tenuiceps. Termites have a short time
to select a mate for life, which should intensify any fitness consequences of inbreeding.
However, alates did not actively avoid inbreeding through mate choice via kin
recognition based on genetic or environmental cues. Furthermore, the majority of
colonies exhibited a female-biased
sex ratio, and none exhibited a male-bias,
indicating
that differential bias does not reduce inbreeding. Sex allocation was generally
female-biased,
as females also were heavier, but the potential fitness effect of this
costly strategy remains unclear. The bacterium Wolbachia, known in other insects
to parasitically distort sex allocation toward females, was present within all alates.
While Wolbachia is commonly associated with termites, parasitism has yet to be demonstrated,
warranting further study of the nature of the symbiosis. Both the apparent
lack of inbreeding avoidance and potential maladaptive sex allocation implies possible
negative effects on mating and fitness.
