DOI: 10.5061/dryad.0vt4b8h79
title: Data from: Too cold to handle: Climatic constraints on arboreal ants in temperate forests

description: The macroscale at which we measure, model, and predict climate change does
 not align with the microscale at which small ectotherms experience
 climate. To understand climate’s influence on biodiversity and potential
 ecological effects of climate change, more work is needed to understand
 how ectotherm physiology relates to microclimatic
 temperatures. Tree canopies are an example of a habitat that
 produces extreme microclimates, and arthropods in tropical forest canopies
 are threatened by extreme heat and warming. The situation in temperate
 canopies, however, is less clear. Conventional wisdom suggests that winter
 cold limits arboreal arthropod diversity in temperate forests, but because
 the canopy is less buffered from extreme temperatures, summer heat could
 also play a role. Heat- and cold-limited communities will respond
 differently to climate change, so this distinction is
 critical. Using the frameworks of the thermal adaptation
 hypothesis and thermal niche asymmetry, we asked whether arboreal ants
 were physiologically adapted to their extreme environment and whether
 summer heat or winter cold was more stressful. We tracked internal
 microclimates of ant nests in the canopy and on the ground over the
 seasonal cycle in temperate forests in North Carolina, USA. Then, we
 measured the heat (CTmax) and cold tolerance (CTmin) of worker ants in
 summer and spring and compared them to the ants’ experienced
 microclimates. Nests in the temperate canopy experienced hotter
 and colder extremes and more closely tracked air temperatures than ant
 nests on the ground. Arboreal ants partially adhered to the thermal
 adaptation hypothesis. They were more heat-tolerant than ground-nesting
 species, but despite experiencing lower temperatures, they were less
 cold-tolerant. Ants acclimated their cold tolerance in line with seasonal
 changes, but heat tolerance was more phylogenetically constrained. Summer
 heat did not approach ants’ heat tolerance in either stratum, but winter
 and spring lows in the canopy exceeded the cold tolerance of ants nesting
 there. By comparing microclimatic temperatures and thermal
 physiology, we show that winter cold—and not summer heat—likely limits
 arthropod diversity in the temperate canopy. As the climate warms, the
 temperate canopy may become accessible to more arthropod species.
description: # Data from: Too cold to handle: Climatic constraints on arboreal ants in
 temperate forests
 [https://doi.org/10.5061/dryad.0vt4b8h79](https://doi.org/10.5061/dryad.0vt4b8h79) ## Description of the data and file structure These are the data underlying the analyses and results of the manuscript titled "Too cold to handle: Climatic constraints on arboreal ants in temperate forests". In this manuscript, we use mesoclimatic (air) and microclimatic (nest) temperatures to assess whether ants in the temperate tree canopy are physiologically adapted to more extreme temperatures and whether they are more limited by summer heat or winter cold. We collected air temperatures in the canopy and on the ground at 5 forest sites. We collected internal nest temperatures from 8 to 10 ant nests in the canopy and on the ground of those same forest sites. We also measured heat and cold tolerance arboreal and terrestrial ant communities in the summer and spring.  ### Files and variables #### File: air\_temps.csv **Description:** Raw air temperature data measured in the canopy and on the ground of 5 temperate forest sites from June 7, 2022 to August 2, 2022 and  October 31, 2022 to April 11, 2023.  ##### Variables * id: HOBO sensor which recorded the temperature; unique id for each HOBO sensor * no: nth record for each sensor * date_time: date and time of temperature recording; format: yyyy-mm-dd hh:mm:ss * temp_c: temperature recorded [°C] * date: date of temperature recording; format mm/dd/yyyy * month: nominal month of temperature recording * day: day of month of temperature recording * hour: hour of day of temperature recording; 0 = 0:00, midnight; 23 = 23:00, 11pm * site: site for which the temperature was recorded; unique id for each site * tree: tree for which the temperature was recorded; unique id for each tree within each site * stratum: vertical stratum in which recording was taken; arboreal/terrestrial #### File: MoreauBell\_matrix\_2013.nex **Description:** Genus-level global ant phylogeny from Moreau & Bell 2013 ([doi: 10.1111/evo.12105)](doi.org/10.1111/evo.12105) #### File: ct\_raw\_nest.csv **Description:** Raw upper and lower thermal tolerance measurements for individual ants from nests in the canopy and on the ground of 5 temperate forest sites.  ##### Variables * nest_code: nest from which the ant measured was collected; unique id for each ant nest consists of [site]-[tree]-[nest] * genus_species: species (or species complex) of the ant measured; format "Genus.species" * assay: indicator of whether the thermal limit measured was CTmax (= max) or CTmin (= min) * ct: recorded thermal limit [°C] * season: indicator of whether the thermal limit was measured in summer 2022 or spring 2023 * site: site from which the ant was collected; unique id for each site * tree: tree from which the ant was collected; unique id for each tree within each site * tree_code: tree from which the ant was collected; unique id of each tree consists of [site]-[tree] * stratum: vertical stratum from which the ant was collected; arboreal/terrestrial * nest: nest from which the ant was collected; unique id for each nest in each tree * assay_no: nominal indicator of whether this ant's thermal tolerance was measured during the first, second, third, or fourth assay of the day * assaycode: assay during which the ant's thermal tolerance was measured; unique id for each assay consists of [site]-[tree]-[assay_no] * tube_no: indicator of ant's location in dry block during assay * specimen_code: unique id of voucher specimen from the same nest  #### File: nest\_temps.csv **Description:** Raw temperature data measured in ant nests in the canopy and on the ground of 5 temperate forest sites from June 7, 2022 to August 2, 2022 and  October 31, 2022 to April 11, 2023. ##### Variables * id: nest from which the temperature was taken; unique id for each nest consists of [site]-[tree]-[nest] * site: site at which the temperature was taken; unique id for each site * tree: tree at which the temperature was taken; unique id for each tree within each site * nest: nest from which the temperature was taken; unique id for each nest within each tree * stratum: vertical stratum from which the temperature was taken; arboreal/terrestrial * microhabitat: microhabitat of the nest from which the temperature was taken; dead wood = dead stump, branch, or log; mound = anthill (typical of* Formica*); squirrel nest = abandoned squirrel nest, typically consisting of decaying leaf litter; tree base = immediately where tree trunk meets the soil, nest could continue down into the root system, soil, or into a cavity within the trunk; tree crotch = nest located in canopy  where main trunk meets major branch, bark structure is rougher than rest of trunk; under rock = nest entrance is under a rock; underground = nest continues into the soil * date_time: date and time at which temperature was recorded; format: yyyy-mm-dd hh:mm:ss * temp_c: temperature recorded [°C] * date: date on which temperature was recorded; format: mm/dd/yyyy * month: nominal month in which temperature was recorded * day: day of month on which temperature was recorded * hour: hour of day in which temperature was recorded; 0 = 0:00, midnight; 23 = 23:00, 11pm ## Code/software All analyses were performed in R 4.3.2 and R Studio 2023.12.1.402. Packages and versions are detailed in the methods of the manuscript.  ThermalMS.R contains all the code necessary for all analyses and figures in the manuscript. It requires three datasets: air_temps.csv, nest_temps.csv, and ct_raw_nest.csv. To recreate the conditional quantile plots in ggplot2, it sources two scripts from the openair package: checkPrep.R and cutData.R, both of which can be found in the zipped folder titled "openair".