Pervasive effects of Wolbachia on host activity

Heritable symbionts have diverse effects on the physiology, reproduction,
and fitness of their hosts. Maternally
transmitted Wolbachia are one of the most common
endosymbionts in nature, infecting about half of all insect species. We
test the hypothesis that Wolbachia alter host behavior
by assessing the effects of 14
different Wolbachia strains on the locomotor activity of
nine Drosophila host species. We find
that Wolbachia alter the activity of six different host
genotypes, including all hosts in our assay infected
with wRi-like Wolbachia strains
(wRi, wSuz, wAur), which have rapidly spread
among Drosophila species in only the last 13,000 years.
While Wolbachia effects on host activity were common,
the direction of these effects varied unpredictably and sometimes depended
on host sex. We hypothesize that the prominent effects
of wRi-like Wolbachia may be explained by
patterns of Wolbachia titer and localization within host
somatic tissues, particularly in the central nervous system. Our findings
support the view that Wolbachia have wide-ranging
effects on host behavior. The fitness consequences of these behavioral
modifications are important for understanding the evolution of
host-symbiont interactions, including
how Wolbachia spread within host populations.