Individual differences

Individuals differ. But what environments or conditions select for more or less such individual variation? In black widows, individual differences increase in social (high density) situations, and decrease with disturbance (both effects during development).

Interestingly, differences across multiple axes often come together in ‘syndromes’ (such that a difference in one axis predicts differences in another). For individual social insects, this is studied in the context of division of labor (see section above), although often the syndromes may not conform to classic interpretations (e.g. be more along axes of low vs. high quality workers or lean/old vs fat/young workers).

Groups, or colonies, also differ. We show here that ant colonies vary along a life-history-related syndrome that is driven by nest site competition.

colony personalities

Temnothorax ant colonies in habitats with high nest site competition invest more in sexuals (reproduction) and less in growth (new workers), and this correlates with a suite of behavioral traits - a life history syndrome at the colony level.

Bengston SE, Dornhaus A 2014 'Be meek or be bold? A colony-level behavioural syndrome in ants', Proceedings of the Royal Society: Biological Sciences 281: 20140518 - pdf - in colonies from habitats across a large geographic range (Western US), field foraging distance correlates negatively with lab aggression, number of foragers, and threat response: these thus form a syndrome (independent of colony size, no of queens, or no of brood) - with more risk-tolerant (fewer, further foragers, more aggressive) colonies at higher latitudes; activity level in the colony without threat does not correlate.

Bengston SE, Dornhaus A 2015 ‘Latitudinal variation in behaviors linked to risk-tolerance is driven by nest-site competition and spatial distribution in the ant Temnothorax rugatulus’, Behavioral Ecology and Sociobiology 69: 1265-1274 - pdf - of a large number of environmental variables (related to competition, predation, resource avail-ability, or environmental stress), nest-site competition best predicts colony behavior (more competition ~ more risk tolerant)

Bengston S, Shin M, Dornhaus A 2017 ‘Life-history strategy and behavioral type: Risk-tolerance reflects growth rate and energy allocation in ant colonies’, Oikos 126: 556-564 - pdf - more risk-tolerant colonies invest more in reproduction (queens/males) and less in growth (new workers)

black widows

Black widows vary in a low vs high investment in foraging (many sticky threads) vs self-defense (better hideout) syndrome; we show that variation among individuals is driven by juvenile experience, and that social environments increase, but disturbance decreases variation.

DiRienzo N, Johnson C, Dornhaus A 2019 'Juvenile social experience generates differences in behavioral variation but not averages', Behavioral Ecology 30: 455–464 - pdf - juvenile experience of high density increases, juvenile experience of disturbance decreases population-level variation in behavior of black widow spiders

DiRienzo N, Schraft HA, Montiglio PO, Bradley CT, Dornhaus A, 2020, ‘Foraging behavior and extended phenotype independently affect foraging success in spiders’, Behavioral Ecology 31, 1242-1249 - pdf - aggressive behavior and number of gumfooted (sticky foraging) silk lines in the web of a black widow spider both and independently increase foraging success

Schraft H, Bilbrey C, Olenski M, DiRienzo N, Montiglio PO, Dornhaus A 2022 Injected serotonin decreases foraging aggression in black widow spiders (Latrodectus hesperus), but dopamine has no effect, Behavioural Processes 204: 104802 - what the title says

DiRienzo N, Bradley CT, Smith CA, Dornhaus A 2019 'Bringing down the house: male widow spiders reduce the webs of aggressive females more' Behavioral Ecology and Sociobiology 73: 1-10 - pdf - males tear down a portion of the females web; this study shows that this probably mostly serves to reduce female cannibalism (instead of signaling or reducing competition from other males)