Mating system evolution and worker caste diversity inPheidoleants

Abstract

The efficiency of social groups is generally optimized by a division of labour, achieved through behavioural or morphological diversity of members. In social insects, colonies may increase the morphological diversity of workers by recruiting standing genetic variance for size and shape via multiply mated queens (polyandry) or multiple-breeding queens (polygyny). However, greater worker diversity in multi-lineage species may also have evolved due to mutual worker policing if there is worker reproduction. Such policing reduces the pressure on workers to maintain reproductive morphologies, allowing the evolution of greater developmental plasticity and the maintenance of more genetic variance for worker size and shape in populations. Pheidole ants vary greatly in the diversity of worker castes. Also, their workers lack ovaries and are thus invariably sterile regardless of the queen mating frequency and numbers of queens per colony. This allowed us to perform an across-species study examining the genetic effects of recruiting more patrilines on the developmental diversity of workers in the absence of confounding effects from worker policing. Using highly variable microsatellite markers, we found that the effective mating frequency of the soldier-polymorphic P. rhea (avg. meN = 2.65) was significantly higher than that of the dimorphic P. spadonia (avg. meN = 1.06), despite a significant paternity skew in P. rhea (avg. B = 0.10). Our findings support the idea that mating strategies of queens may co-evolve with selection to increase the diversity of workers. We also detected patriline bias in the production of different worker sizes, which provides direct evidence for a genetic component to worker polymorphism.

Age, worksite location, neuromodulators, and task performance in the ant Pheidole dentata

“…Monoandry appears to be the rule in Pheidole (Huang et al 2013), although quantitative data does not exist for P. dentata . Nests consisted of test tubes partially filled with water and plugged tightly with cotton and placed in a plastic box lined with Fluon® (Insect-a-slip, Bioquip Inc.).…”

Eusocial insects as emerging models for behavioural epigenetics

“…Although such consideration of genetic effects may complicate straightforward analyses of the role of environmental and epigenetic effects on behaviour, it remains an important factor that should be examined. To this end, it would be particularly revealing to use a monogamous but dimorphic species, as may be found in the Camponotus or Pheidole genera (BOX 2), to assess whether genetic variation that is solely due to maternal heterozygosity is also associated with caste fate or worker behaviour 92,108 . Nonetheless, the often-invoked metaphor that dichotomizes nature and nurture should be replaced by an integrated view of nature plus nurture, in which both genetic and environmental factors have complementary modulatory roles in directing the ontogenetic trajectory of an individual 98 (FIG.…”

Biogenic Amines and Collective Organization in a Superorganism: Neuromodulation of Social Behavior in Ants

“…Genetic diversity in colonies of different ant species, for example, varies with the degree of polyandry (multiple mating by the queen) and polygyny (the presence of multiple queens in a colony) and is considered beneficial to the efficiency of a colony's ergonomic operations [Waibel et al, 2006]. Behavioral specialization of groups -either castes or worker subcastes and age cohorts -within a colony may reflect genetic variation associated with worker patrilines [Evison and Hughes, 2011;Schluns et al, 2011;Huang et al, 2013;Smith et al, 2013] that could code for differences in monoamine synthesis or receptors and thus the neuromodulation of behavior [Donaldson and Young, 2008;Krugel et al, 2009]. Variation in monoamine action could be associated with patrilineal or matrilineal differences in worker response thresholds for task attendance, influencing sensitivity to cues or task-related pheromones and other social signals correlated with division of labor.…”