DOI: 10.5061/dryad.7q3j8
title: Data from: Microhabitat and body size effects on heat tolerance: implications for responses to climate change (army ants: Formicidae, Ecitoninae)

description: 1. Models that predict organismal and population responses to climate
 change may be improved by considering ecological factors that affect
 species thermal tolerance. Species differences in microhabitat use can
 expose animals to diverse thermal selective environments at a given site
 and may cause sympatric species to evolve different thermal tolerances. 2.
 We tested the hypothesis that species differences in body size and
 microhabitat use (above- vs. below-ground activity) would correspond to
 differences in thermal tolerance (maximum critical temperatures: CTmax).
 Thermal buffering effects of soil can reduce exposure to extreme high
 temperatures for below-ground active species. We predicted larger-bodied
 individuals and species would have higher CTmax and that species mean
 CTmax would covary positively with degree of above-ground activity. We
 used Neotropical army ants (Formicidae: Ecitoninae) as models. Army ants
 vary in microhabitat use from largely subterranean to largely above-ground
 active species and are highly size polymorphic. 3. We collected data on
 above- and below-ground temperatures in habitats used by army ants to test
 for microhabitat temperature differences, and we conducted CTmax assays
 for army ant species with varying degrees of surface activity and with
 different body sizes within and between species. We then tested whether
 microhabitat use was associated with species differences in CTmax and
 whether microhabitat was a better predictor of CTmax than body size for
 species that overlapped in size. 4. Microhabitat use was a highly
 significant predictor of species' upper thermal tolerance limits,
 both for raw data and after accounting for the effects of phylogeny.
 Below-ground species were more thermally sensitive, with lower maximum
 critical temperatures (CTmax). The smallest workers within each species
 were the least heat tolerant, but the magnitude of CTmax change with body
 size was greater in below-ground species. Species-typical microhabitat was
 a stronger predictor of CTmax than body size for species that overlapped
 in size. Compared to the soil surface, 10-cm subsoil was a significantly
 moderated thermal environment for below-ground army ants, while maximum
 surface raid temperatures sometimes exceeded CTmax for the most thermally
 sensitive army ant castes. 5. We conclude sympatric species differences in
 thermal physiology correspond to microhabitat use. These patterns should
 be accounted for in models of species and community responses to thermal
 variation and climate change.
description: CTmax
 dataAll data in this file
 was collected in the field. Data were input manually. These data were used
 for all analyses having heat-tolerance as a response variable. Species
 codes were used: Ebparvi = Eciton burchellii parvispinum, ECITmexi =
 Eciton mexicanum, LABIcoec = Labidus coecus, LABIprae = Labidus praedator,
 LABIJTL001 = Labidus JTL001, LABIspin = Labidus spininodis, NEIVpilo =
 Neivamyrmex pilosus, NEIVmacr = Neivamyrmex macrodentatus, NEIVsumi =
 Neivamyrmex sumichrastiiButton air
 temperaturesThese data were
 collected in the field using calibrated ibutton temperature loggers
 (model: thermochron, Maxim Integrated). OneWireViewer software was used to
 read probes.ibutton temperatures to
 submit.xlsxMax & Min surface
 temperaturesThese data are maximum
 and minimum surface temperatures collected at 40 surface army ant raids in
 Monteverde, Costa Rica using infrared thermometers.MaxMin IR raid temps to
 submit.xlsxSpecimen head
 widthsThese are a collection
 of head-width measurements used to calculate means for each
 visually-discerned size category. Specimens were stored together within
 each body size category. Specimens were photographed under a dissecting
 microscope, and measured using ImageJ.Head width table to
 submit.xlsx