Are ecological communities the seat of endosymbiont horizontal transfer
and diversification? A case study with soil arthropod community.
Abstract
Maternally inherited endosymbionts are one of the most abundant bacteria
infecting arthropods and show extensive horizontal transfer. Such
widespread distribution and extensive recombination among these
endosymbionts could be an outcome of horizontal transfer as for such
genetic exchanges to occur their hosts should come in contact. One such
level of biological organization where different hosts can do that is
the ecological community. Despite various studies focusing on known
model species and specific ecological interactions among hosts, reports
on community wide endosymbiont data are rare. To better understand
endosymbiont spread, we investigated the incidence, diversity, extent of
horizontal transfer and recombination of three such endosymbionts
(Wolbachia, Cardinium and Arsenophonus) in a specific soil arthropod
community. Wolbachia strain characterization was done using multiple
genes whereas single 16S rRNA gene was used for Cardinium and
Arsenophonus. Amongst 3509 individual host arthropods belonging to 390
morphospecies, 12.05% were infected with Wolbachia, 2.82% with
Cardinium and 2.05% with Arsenophonus. Phylogenetic incongruence
between host and endosymbiont indicated extensive horizontal transfer of
endosymbionts within this community. Three cases of recombination
between Wolbachia supergroups and eight incidences of within supergroup
genetic exchange were also found. Statistical tests of similarity
indicated supergroup A Wolbachia and Cardinium to show a pattern
consistent with rapid horizontal transfer within the community. However
same tests done for super group B Wolbachia and Arsenophonus did not
show similar patterns. We highlight the importance of extensive
community wide studies for a better understanding of the spread of
endosymbionts across global arthropod communities.