Colony pace: a life-history trait affecting social insect epidemiology

Abstract

Among colonies of social insects, the worker turnover rate (colony 'pace') typically shows considerable variation. This has epidemiological consequences for parasites, because in 'fast-paced' colonies, with short-lived workers, the time of parasite residence in a given host will be reduced, and further transmission may thus get less likely. Here, we test this idea and ask whether pace is a life-history strategy against infectious parasites. We infected bumblebees (Bombus terrestris) with the infectious gut parasite Crithidia bombi, and experimentally manipulated birth and death rates to mimic slow and fast pace. We found that fewer workers and, importantly, fewer last-generation workers that are responsible for rearing sexuals were infected in colonies with faster pace. This translates into increased fitness in fast-paced colonies, as daughter queens exposed to fewer infected workers in the nest are less likely to become infected themselves, and have a higher chance of founding their own colonies in the next year. High worker turnover rate can thus act as a strategy of defence against a spreading infection in social insect colonies.

Social Immunity: Emergence and Evolution of Colony-Level Disease Protection

“…Infected honey bees also switch faster to out-of-hive tasks, which could reduce disease transmission within the hive (99). Moreover, an experimental increase in colony pace, achieved through a faster turnover of workers, reduced pathogen load in the colony (25). Hence, social insects have evolved many resistance mechanisms to reduce pathogen load and prevent infections by a wide diversity of pathogens.…”

“…Novel technologies such as automated monitoring, machine learning, and network analyses (95,120,127,146) offer us powerful tools to address the organizational immunity hypothesis, as well as a refined view of how local interactions and information exchange can produce emergent properties (95,104). Combining these technologies with methods to quantify pathogen spread (25,56,81) offers a potentially promising approach for understanding how disease defenses function at the colony level (139).…”

Sociality and parasite transmission

“…This point will take longer to reach in larger social groups, when no lasting primed immunity exists. Similarly, when, by births, new and naïve group members are recruited into the society frequently enough, there will always be enough new hosts to infect, and the within-group transmission can continue (Büchel and Schmid-Hempel 2016 ). Finally, if new variants appear in the parasite population at a sufficiently high rate, within-group transmission will also continue.…”

Ants’ Personality and Its Dependence on Foraging Styles: Research Perspectives

“…The opportunities and challenges associated with including personality within the POLS concept have been initially proposed by Wolf et al (2007); Careau et al (2008), and Réale et al (2010) and considered in many species including non-social insects. Recently, the POLS concept has been applied to bumblebees (Buechel and Schmid-Hempel, 2016), gypsy Aphaenogaster ants (Blight et al, 2016), and rock Temnothorax ants (Bengston et al, 2017). Segev et al (2017) examined the persistence of behavioral syndromes at colony levels in T. longispinosus along a climatic gradient in North-Eastern United States.…”