Does the evolution of division of labour require accelerating returns from individual specialisation?

Recent theory has overturned the assumption that accelerating returns from individual specialisation are required to favour the evolution of division of labour. Yanni et al. (2020) showed that topologically constrained groups, where cells cooperate with only direct neighbours such as for filaments or branching growths, can evolve a reproductive division of labour even with diminishing returns from individual specialisation. We developed a conceptual framework and specific models to investigate the factors that can favour the initial evolution of reproductive division of labour. We found that selection for division of labour in topologically constrained groups: (1) is not a single mechanism to favour division of labour – depending upon details of the group structure, division of labour can be favoured for different reasons; (2) always involves an efficiency benefit at the level of group fitness; and (3) requires a mechanism of coordination to determine which individuals perform which tasks. Given that such coordination is unlikely to evolve before division of labour, this limits the extent to which topological constraints could have favoured the initial evolution of division of labour. We conclude by suggesting experimental designs that could determine why division of labour is favoured in the natural world.

Seasonal variation in the invertebrate community and diet of a top fish predator in a thermally stable spring

Many life-history events in aquatic invertebrates are triggered by seasonal changes in water temperature, but other ecological factors may be important as well. To rule out the confounding effects of changing water temperature, we studied the seasonal dynamics of an aquatic invertebrate community and their effect on a top fish predator in a thermally stable freshwater spring in South Iceland. We sampled benthic invertebrates five times over a year and conducted a mark-recapture study on the top predator in the system, small benthic Arctic charr, Salvelinus alpinus (L.). We assessed variation in diet composition and feeding preferences by calculating the electivity and individual specialisation of each fish at each sampling time. There was a clear separation of winter and summer communities for the benthic invertebrates. The variation in prey availability was also reflected in the fish diet, with higher feeding selectivity in summer than in winter for the highly abundant Chironomidae larvae. In contrast, individual specialisation as a measure of intrapopulation niche variation was higher in winter when prey availability was lower. We furthermore found that groundwater amphipods might play an important role in the winter diet of spring-dwelling Arctic charr. In conclusion, seasonal variation in the invertebrate community is an important factor to consider and has the potential to alter the phenotype (e.g. growth rates) and behaviour (e.g. feeding preferences) of higher trophic levels.

Foraging fidelity and individual specialisation in a temperate bat Myotis Nattereri

Bat populations have declined globally over the last century largely due to anthropogenic change. Many temperate forest species of bat appear loyal to their foraging sites however, conservation of these sites rather than just habitat types is rarely considered and is essential to protect bat populations. It is not clear whether site fidelity in bats is species-specific or a more general trait or why it is exhibited but behaviour patterns could be important for conservation and management objectives. Foraging variation may occur due to ‘individual specialisation’, such that individuals differ significantly in their prey or habitat utilisation, independent of class-effects. If bats do exhibit individuality in their habitat choice, then protection of a mosaic of habitats rather than single preferred habitat per species may be critical to their conservation.The goal here was to determine whether Natterer’s bats show fidelity in their foraging choices and whether they show individual specialisation in their foraging habits.Thirty-four individual bats were tracked for at least one full night, from two different sites.Site fidelity in Natterer’s was consistent across a range of intervals (months and years) despite contrasting seasonal contexts. Individuals repeatedly exploited specific foraging locations and showed individual specialisation in their habitat use which is consistent with the behaviour of a territorial species.Studies designed to inform conservation and management of temperate bats should attempt to maximize the number of individuals from which movement data is sought, whilst ensuring that data represent a coherent and meaningful measure of behaviour such as a single full night. Bat conservation may need to shift from general descriptions of habitat preferences to considering individual specialisation in habitat use. Designing conservation strategies resilient to environmental change might then advocate protecting a mosaic of habitats to preserve the habitat specialisms of many individuals and enhance their productivity rather than advocating the preservation of a single preferred habitat only suited to a few individuals.