Life Inside an Acorn: How Microclimate and Microbes Influence Nest Organization in Temnothorax Ants

Abstract

Nests provide a buffer against environmental variation, but conditions may also vary at different locations within a nest. Conditions can vary based on abiotic factors, such as moisture and temperature, as well as biotic factors, such as the presence of microbes and potential pathogens. Therefore, characterizing how animals adjust their position inside their nests to track microclimate preferences while at the same time preventing pathogen exposure is necessary to understand the benefits nests provide. Here we studied how colonies of the acorn‐nesting ant Temnothorax curvispinosus responded to experimental manipulation of moisture, temperature, and microbial growth inside their nests. Colonies showed no response to differences in moisture and moved to the bottom of the acorn regardless of moisture treatment. When nests were heated from the top to simulate warming by the sun, workers preferentially moved brood to the warm, upper half of the acorn, which would stimulate brood development. Finally, the strongest factor that influenced colony position was the presence of microbes inside the nest—colonies avoided the bottom of the nest when it was inoculated with microbes, and colonies in new acorns shifted to the top of the acorn over time as mold and other microbes had time to grow. The relatively strong response of T. curvispinosus to microbial growth inside their nests suggests that pathogen pressures—in addition to microclimate—have a significant impact on how colonies use nest spaces. Social insects are known to invest heavily in antimicrobial compounds that kill or slow the growth of microbes, but avoidance may represent an additional line of defense to prevent pathogen exposure.

Urbanization without isolation: the absence of genetic structure among cities and forests in the tiny acorn ant Temnothorax nylanderi

“…[45,47]) identified conserved functional genomic units involved in social behaviour traits, their potential role in adaptation to urban habitats was not investigated. Group living, by allowing workers to manipulate the environment of the developing larvae, could buffer environmental variations between urban and forest environments [55,56]. Nevertheless, we found signatures of divergent selection between urban and forest sites, potentially linked to sociality (table 2).…”

Azteca ants maintain unique microbiomes across functionally distinct nest chambers

“…It is possible that C. jadinii yeast may be initially beneficial but may become pathogenic above some abundance threshold. Colonies of the acorn-nesting ant Temnothorax curvispinosus avoid regions of their nests that become overgrown with microbes, which suggest that even relatively benign microbes can have negative impacts on ants when microbes reach high abundances [67]. Whether the presence of C. jadinii is harmful for A. alfari is an important next step for understanding the microbial symbionts in this Cecropia-Azteca mutualism.…”

Decreasing worker size diversity does not affect colony performance during laboratory challenges in the ant Temnothorax nylanderi

“…For instance, in cellbuilding social insects, the size of individuals is controlled by the quantity of food provided by workers in the cell Kapheim et al 2011;Linksvayer et al 2011;Brand and Chapuisat 2012) and not only by the ability of larvae to grow. Many species can also control the abiotic environment experienced by larvae; for example, Apis mellifera honeybees, red wood ants of the Formica rufa group and Temnothorax ants limit temperature fluctuations in their nests (Rosengren et al 1987;Fahrenholz et al 1989;Karlik et al 2016). Temnothorax ants, despite nesting in small preformed nests, can display social canalization: under deteriorated environmental conditions, colonies readily migrate to better nests (Dornhaus et al 2004).…”