Martha S. (Molly) Hunter, Professor
Department of Entomology, The University of Arizona
"Environmental transmission of insect symbionts: upending our assumptions about the intimacy of mutualist microbe associates"
It is widely known that arthropods have important relationships with microbes that shape their reproduction and ecology. In general, insect biologists have focused their attention on uncultivable, intracellular, strictly maternally inherited bacteria that by definition, have a durable evolutionary relationship with their hosts. They may be nutritional mutualists, defensive mutualists, or may manipulate host reproduction in ways that boosts their own transmission to the next host generation. More recently, we have come to appreciate the diversity and importance of extracellular, horizontally or environmentally acquired symbionts. These symbionts tend to have a less intimate relationship with their hosts, and while they may benefit their hosts, we think of them as being less critical for host success, and as likely to be pathogens or commensals.
I will touch on some of the intracellular symbiont systems we have studied, e.g. Hamiltonella, which defends aphid hosts against their parasitoid natural enemies, Cardinium, which causes parthenogenesis and a crossing defect called cytoplasmic incompatibility in whitefly parasitoids, and Rickettsia, which appears to show a range of relationships with its whitefly host. I will then turn to new work in our laboratory, studying an environmentally-inherited, nearly obligate bacterial gut associate, Burkholderia, of the coreid bug pest, Leptoglossus zonatus. We find that while the acquisition of the symbiont is not guaranteed, the consequences of not acquiring the symbiont is disastrous, and that not all symbionts have equal fitness consequences for the bugs. The long-standing assumption, then, that environmentally acquired symbionts are less critical for host success must be re-examined in light of this and other examples.
Monday, March 9 at 4:00pm to 5:00pm
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