The influence of symbiotic bacteria on reproductive strategies and wing polyphenism in pea aphids responding to stress

Abstract

1. Environmental stressors can be key drivers of phenotypes, including reproductive strategies and morphological traits. The response to stress may be altered by the presence of microbial associates. For example, in aphids, facultative (secondary) bacterial symbionts can provide protection against natural enemies and stress induced by elevated temperatures. Furthermore, aphids exhibit phenotypic plasticity, producing winged (rather than wingless) progeny that may be better able to escape danger, and the combination of these factors improves the response to stress. How symbionts and phenotypic plasticity, both of which shape aphids' stress response, influence one another, and together influence host fitness, remains unclear.2. In this study, we investigate how environmental stressors drive shifts in fecundity and winged/wingless offspring production, and how secondary symbionts influence the process. We induced production of winged offspring through distinct environmental stressors, including exposure to aphid alarm pheromone and crowding, and, in one experiment, we assessed whether the aphid response is influenced by host plant.3. In the winged morph, energy needed for wing maintenance may lead to trade-offs with other traits, such as reproduction or symbiont maintenance. Potential tradeoffs between symbiont maintenance and fitness have been proposed but have not been tested. Thus, beyond studying the production of offspring of alternative morphs, we also explore the influence of symbionts across wing/wingless polyphenism as well as symbiont interaction with cross-generational impacts of environmental stress on reproductive output. 4. All environmental stressors resulted in increased production of winged offspring and shifts in fecundity rates. Additionally, in some cases, aphid host-by-symbiont interactions influenced fecundity. Stress on first-generation aphids had cross-generational impacts on second-generation adults, and the impact on fecundity was further influenced by the presence of secondary symbionts and presence/ absence of wings. | Journal of Animal EcologyREYES Et al. | 603Journal of Animal Ecology REYES Et al.

A Laterally Transferred Viral Gene Modifies Aphid Wing Plasticity

“…10 genotypes produced a low percentage of winged-offspring after crowding (weakly inducible genotypes: genotypes 73, 88, 183, 218, 223, 248, 375, 396, 405, & 495), and 10 genotypes produced a high percentage of winged-offspring (highly inducible genotypes: genotypes 42, 125, 179, 202, 217, 281, 286, 445, 473, & 500). We specifically chose genotypes that did not harbor the facultative endosymbiont Regiella insecticola as previous work has suggested that infection with this bacterium alters wing induction [24]. We also verified that these genotypes did not harbor DplDNV using established PCR protocols [3].…”

Abdominal microbial communities in ants depend on colony membership rather than caste and are linked to colony productivity

“…An important role of microbial symbionts for host fitness has been found for a taxonomically diverse group of insects (e.g., Coon, Brown, & Strand, 2016;Reyes et al, 2019;Schwab, Riggs, Newton, & Moczek, 2016). Thus, we tested for associations between abdominal microbial community composition and proxies for colony fitness such as brood quantity and colony size.…”

More Is Not Always Better: Coinfections with Defensive Symbionts Generate Highly Variable Outcomes

“…Symbiont infection increases aphid survival and reproduction while decreasing fungal spore production from deceased aphids (27,31,65). R. insecticola has also been associated with changes in the propensity for wing development, possibly with host plant utilization, and with the timing of sexual reproduction in pea aphids (66)(67)(68)(69). Currently, there are no reports that it confers protection against parasitoids in pea aphids (29,35,47).…”