Sociobiology on the fly; understanding social interactions in multispecies groups
Amanda Bretman (School of Biology, University of Leeds) and Xavier Harrison (University of Exeter)
The effects of social environments on individuals are widespread, even in species not classically thought of as social (Bailey and Moore 2018). These can range from reproductive decisions (Bretman et al 2009) to ageing (Leech et al 2017; Fricke and Bretman 2019), stress and immune responses (Leech et al 2019), and even differences in host microbiomes (Tung et al 2015; Leech, McDowall et al in prep). The picture is complicated because often these effects are sex-specific and depend on the age of the interacting partners. For example, in terms of lifespan and decline in physical functions, males are more sensitive to contact with other males, but females are highly sensitive to contact with males (Leech et al 2017, Fricke and Bretman 2019). Requires
However, whilst we think of social environments as interactions between conspecifics, species are rarely found in single species groups. Clearly this can alter competition for resources such as food, but effects are likely to influence individuals in multiple ways even beyond this direct competition, for example by acting as a source of pathogenic or mutualistic bacteria. For example, males respond to the presence of other males, which signals mating competition. We have shown that males will produce some responses to males of some but not all heterospecifics (Fig 1 Bretman et al 2017).
Others have shown that aggression between males depends on the species identity of the males involved, with more closely related species being subjected to as much aggression as conspecifics (Gupta et al 2019). In recent experiments we have found that conspecific contact is important for male cognitive abilities (increases learning and memory), but heterospecifics do not have any effect, yet for females the opposite is true (Rouse et al in prep). Moreover, these behavioural differences go hand in hand with gene expression changes, suggesting that conspecific/ heterospecific social environments have differential effects at the molecular level. Therefore species recognition seems more or less important depending on which behaviours or traits are being studied, and it has been suggested that this is one reason why complex sensory cue systems have evolved in the ability to produce socially-plastic responses (Dore et al 2018).
One extremely exciting area to explore is the role of the microbiome, itself a community of bacteria within the host. Our recent work has shown that in fruit flies, the host’s social environment alters its microbiome, but in sex and age specific ways (Leech, McDowall et al in prep). The fruit fly microbiome is constantly replenished by ingesting bacteria from the environment (Blum et al 2013) and impacts a wide variety of host traits (Broderick and Lemaitre 2012). It is therefore likely that species sharing the same food resource will develop similar microbiomes, and this might have differential effects on their fitness depending on the specific host-microbe interactions. There is a great deal of potential here for a novel assessment of host-microbe-host dynamics in a highly controlled experimental way.
Our aim is to investigate the multifaceted social effects in a wider community ecology framework. We will use fruit flies as a model, as in much of the work referenced above. In the wild, flies live in multispecies groups (Atkinson 1979), so interact with conspecifics and heterospecifics regularly. Different fly species can be easily cultured together and are highly amenable to experimental manipulation (Fig 2). This means we can investigate the influence of multispecies groups on a range of individual traits whilst controlling for resource availability. We will test interspecies social effects on fundamental life history traits such as lifespan and reproductive output, whether interactions are symmetrical or unidirectional (i.e. whether two species have the same effect on each other), and investigate potential mechanisms such as sensory cues and the role of the microbiome. This will advance our understanding of sociobiology beyond single species interactions.
This project is using molecular and ecological tools to address fundamental and crucial questions relevant to climate change biology, conservation biology, evolution and adaptation. The project will produce several publishable papers, with at least one expected to be high impact as the questions being addressed are of wide scientific interest. The candidate will also be expected to present their research at both national and international conferences.
A strong undergraduate (and ideally Masters) degree in ecology, genetics, biology or zoology is expected. Experience in using insects in a lab and some statistics background would be helpful. However, training will be provided in all techniques relevant for the project. If you are not sure if you have the relevant background please feel free to contact the supervisors to discuss the project.
This project will provide students with broad training in a range of techniques associated with population monitoring, phenotypic measurements, life history measurements and molecular / genetic analysis. The work blends community and behavioural ecology with genetics, providing a broad foundation for a future career. The PhD student will have access to a range of training courses designed to facilitate skills development and will be expected to present the outcomes of this project at both national and international conferences.
Research context and partners
The supervisory team have active research groups and strong records of relevant research in molecular mechanisms of phenotypic plasticity and population, community and evolutionary ecology. The student will be involved in fortnightly team meetings, as well as having access to both formal (Faculty) and informal (Ecology & Evolution group) seminar series through the School of Biology. Co-supervision will involve meetings between all participants and the co-supervisor will provide guidance on the overall direction of the project. There is also the opportunity to link with other NERC funded projects that both supervisors are involved in e.g. Bretman is currently co-supervising a project on thermal effects on fertility and on social effects on female reproduction, and Harrison on microbial community dynamics and disease in amphibians. The student will therefore be integrated into the local and national biology community.
Atkinson 1979 A field investigation of larval competition in domestic Drosophila. J Anim Ecol, 48, 91–102.
Bailey and Moore 2018. Evolutionary consequences of social isolation. Trends Ecol & Evol, 33, 595-607.
Blum et al 2013. Frequent replenishment sustains the beneficial microbiome of Drosophila melanogaster. MBio, 4, e00860-13.
Broderick and Lemaitre 2012. Gut-associated microbes of Drosophila melanogaster. Gut Microbes, 3, 307-321.
Bretman et al (2009) Plastic responses of male Drosophila melanogaster to the level of sperm competition increase male reproductive fitness. Proc R Soc B 276, 1705-1711
Bretman et al (2017) The role of species-specific sensory cues in male responses to mating rivals in D. melanogaster fruitflies. Ecol & Evol, 7, 9247.
Bretman & Fricke (2019) Exposure to males, but not receipt of sex peptide, accelerates functional aging in female fruit flies Funct Ecol 2019, 1
Dore et al (2018) The role of complex cues in social and reproductive plasticity. Behav Ecol & Sociobiol 72, UNSP124
Gupta et al (2019) Aggression and discrimination among closely versus distantly related species of Drosophila Royal Society Open Science 6; 190069
Leech et al. (2017) Sex-specific effects of social isolation on ageing in Drosophila melanogaster. J Insect Physiol, 102, 12-17.
Leech et al (2019) Interactive effects of social environment, age and sex on immune responses in Drosophila melanogaster J Evol Biol
Tung et al 2015. Social networks predict gut microbiome composition in wild baboons. eLife, 4, e05224.