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The early life of a leaf-cutter colony constrains symbiont vertical transmission

Citation

Phillips, Zachary; Reding, Luke; Farrior, Caroline (2022), The early life of a leaf-cutter colony constrains symbiont vertical transmission , Dryad, Dataset, https://doi.org/10.5061/dryad.8sf7m0cnt

Abstract

The early life of a leaf-cutter colony is characterized by the dispersal of a female alate (winged “queen”) carrying a fungal pellet, and the subsequent establishment of a foundress (workerless “queen”) raising her incipient fungal garden and colony. The symbiotic roach Attaphila fungicola hitchhikes on female alates during leaf-cutter nuptial flights, which strongly suggests that roaches are vertically transmitted to foundresses and their incipient colonies; however, weak compatibility between roaches and incipient gardens may constrain roach vertical transmission. 

This dataset contains data from an experiment in which the mortality of incipient fungal gardens and foundresses were scored in treatments with or without Attaphila roaches. Additionally, in roach trials we noted whether or not the roaches disturbed fungal gardens during observational bouts conducted during the experiment (see below for more detailed description of behavioral observations). Contrary to traditional assumptions, our results indicate that roaches harm incipient gardens, suggesting that roaches are not well adapted to use vertical transmission between colonies.

 

Methods

This dataset was collected during experiments that were conducted with all replicates kept and observed at room temperature ( 22 - 24°C) in a lab at UT Austin. Chambers were checked for 1 minute every 24 hours in low-light conditions to determine mortality of fungal gardens, foundresses and roaches. The fungal garden was marked as effectively dead if it was dismantled and scattered in decaying clumps in upper and/or lower corners of the chamber and if the foundress did not tend any portion of the garden for at least 30 seconds (“uncaring” foundresses), or if the foundress was dead (without a caretaker, the fungal garden is effectively dead). Alternatively, the fungal garden was marked as living if the foundress tended a contiguous portion of the garden for at least 30s (i.e., the foundress’ head and mandibles maintained a position facing and over the garden, typically manipulating and antennating it).  Additionally, 30 minutes following initial set-up, each foundress chamber was observed for 3 minutes to determine if the inhabiting roach disturbed the incipient garden. Garden disturbance was scored if roach contact caused any observable movement, physical dislocation or fragmentation of the garden, and subsequently we categorized gardens as either “disturbed” (one or more observations of roach disturbance) or “undisturbed” (no observations of roach disturbance).  

For the experiment, we collected paired female alate ants and roaches for use in the experiment, where ants collected from the field already had attached A. fungicola roaches. Using naturally paired ants and roaches ensured that both species came from the same natal colony, and thus controlled for potential intercolony differences (e.g., chemical profiles). We removed the wings of the female alates and placed the de-winged alate (herein, “foundress”) and her attached roach in a 5 cm. diameter container (“foundress chamber”) with 20 mg of fungal garden (“incipient garden”) from a lab colony. Notably, 20 mg is larger than the inoculum of fungus that foundresses initially regurgitate when founding a new colony under natural conditions (Marti et al. 2015).  Long-term survival in the laboratory of foundresses provided only with their inoculum is extremely rare complicating experimentation and highlighting the extreme fragility of this developmental stage.

Usage Notes

Decriptions of variable labels in dataset:

(1) Foundress + Roach: Treatment with foundress and fungal garden and roach 

(2) No Roach:  Treatment with foundress and fungal garden (but no roach)

(3) Flight: female alates and roaches collected during first (marked "1") or second (marked "2") flight

(4) Chamber: Individual number assigned to each artifical foundress chamber during mortality experiment

(5) day_fg_mortality: day of mortality of fungal garden in artificial foundress chamber. "0" indicates fungal garden did not die during experiment.

(6) result: indicates if foundress was dead (marked "dead") or was not caring for fungal garden (marked "uncaring") on day of fungal garden death. An absent value indicates the fungal garden did not die during experiment and was still being cared for by foundress.

(7) nest: name of leaf-cutter ant colony from which female alates and roaches were collected 

(8) Fg_disturb: denotes if roach was observed disturbing fungal garden. "1" indicates roach disturbed fungal garden during observational bout, "0" indicates roach did not disturb fungal garden during observational bout.