Programme REID 2012x - Inra

EVOLUTIONARY DYNAMICS OF SYMBIOTIC COMMUNITIES: A CASE STUDYIN PROTIST ASSEMBLAGES LIVING IN THE HINDGUT OF TERMITESF Dedeine 1 , S Guyot 1 , S Dupont 1 , J Bertaux 2 , C Dupuy 1 ,A-G Bagnères 1 & D Bouchon 21 Institut de Recherche sur la Biologie de l'Insecte, UMR CNRS 6035, Tours2 Laboratoire Ecologie, Evolution, Symbiose, UMR CNRS 6556, PoitiersMany arthropod hosts do not harbor a single symbiont species but instead possess a high diversityof symbionts, which constitute veritable communities (or assemblages) within their habitat hosts.Although new technologies have improved our capacity to study the diversity of such symbioticassemblages, the nature of the interactions existing among symbionts within hosts (conflict orcooperation?), their respective impacts on the extended phenotype of hosts, as well as themechanisms by which symbionts are transmitted through host generations constitute centralquestions that remain unanswered. Protist assemblages living in the hindgut of termites provideunique model systems to answer these questions.Several protist lineages (Parabasalids and Oxymonads) are necessary for the survival of lowertermites because these gut symbionts are required for the degradation of lignocellulose. On the otherhand, these protists are usually strictly anaerobic and cannot survive outside their host habitats.Therefore, one would expect that such inter-dependent associations would be evolutionary stable,exhibiting a general pattern of co-cladogenesis. However, a recent study in subterranean termites(genus Reticulitermes) revealed no strict congruence between the phylogeny of the protists and thephylogeny of their hosts (Dedeine et al. in prep). Furthermore, this study suggests that termite speciescan regularly lose some protist species and gain others. During this talk, we will present results on themechanisms by which termite colonies can lose and gain protists within populations.Mots-clés : Symbiose, évolution, communautés symbiotiques, conflit, coopération, termites9