Bacterial symbionts in insects or the story of communities affecting communities

Abstract

Bacterial symbionts are widespread in insects and other animals. Most of them are predominantly vertically transmitted, along with their hosts' genes, and thus extend the heritable genetic variation present in one species. These passengers have a variety of repercussions on the host's phenotypes: besides the cost imposed on the host for maintaining the symbiont population, they can provide fitness advantages to the host or manipulate the host's reproduction. We argue that insect symbioses are ideal model systems for community genetics. First, bacterial symbionts directly or indirectly affect the interactions with other species within a community. Examples include their involvement in modifying the use of host plants by phytophagous insects, in providing resistance to natural enemies, but also in reducing the global genetic diversity or gene flow between populations within some species. Second, one emerging picture in insect symbioses is that many species are simultaneously infected with more than one symbiont, which permits studying the factors that shape bacterial communities; for example, horizontal transmission, interactions between host genotype, symbiont genotype and the environment and interactions among symbionts. One conclusion is that insects' symbiotic complements are dynamic communities that affect and are affected by the communities in which they are embedded.

Detection of a novel intracellular microbiome hosted in arbuscular mycorrhizal fungi

“…Buchnera's association with aphids is ancient, being approximately 200 million years old and revolves around the endosymbiont's capacity to synthesize essential amino acids for its host (van Ham et al, 2003). Due to their pleiotropic effects on their hosts, the situation is not so clear-cut for the non-essential (secondary) endosymbionts, as their transmission may be both vertical and horizontal and the ratio between cost and benefits strictly depends on environmental conditions (Ferrari and Vavre, 2011).…”

“…In addition to their obligate biotrophy (Bonfante and Genre, 2010), many of them harbor endobacteria in their cytoplasm (Bonfante and Anca, 2009). Bacterial endosymbionts are widespread among animals (Wernegreen, 2012;McFall-Ngai et al, 2013) and in particular the ones living in insect tissues have been investigated in depth (Ferrari and Vavre, 2011). In contrast, examples of endobacteria living inside the fungal cells are much more limited (Bianciotto et al, 2003;Partida-Martinez and Hertweck, 2005;Lackner et al, 2009;Naumann et al, 2010;Kai et al, 2012).…”

Community genetics: what have we accomplished and where should we be going?

“…number of genotypes) increases diversity of associated arthropod communities, confers greater resilience to biotic and abiotic stressors, and affects key aspects of ecosystem function [21,27,28,[31][32][33][34][35]. Recently, studies have begun to extend the scope of community genetics research to examine how genetic variation and population divergence within herbivorous insects, endosymbionts [36][37][38] and predaceous fishes [39][40][41][42] have cascading bottom-up and topdown effects within communities. And finally, a related area of research labelled 'eco-evolutionary dynamics' has shown that evolution within prey populations can influence predator-prey dynamics within microcosms [43 -45].…”

Unpredicted impacts of insect endosymbionts on interactions between soil organisms, plants and aphids

“…However, such studies of two-way interactions (e.g. between a plant and its herbivore or an insect herbivore and its symbionts) cannot always predict the responses of organisms in a community [7][8][9]. Here, we adopt a community approach and simultaneously examine the role of both plant -and insect -microbial interactions in modulating the plant -herbivore interaction.…”