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Thermal diversity of North American ant communities: Cold tolerance but not heat tolerance tracks ecosystem temperature
Author(s) -
Bujan Jelena,
Roeder Karl A.,
Beurs Kirsten,
Weiser Michael D.,
Kaspari Michael
Publication year - 2020
Publication title -
global ecology and biogeography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.164
H-Index - 152
eISSN - 1466-8238
pISSN - 1466-822X
DOI - 10.1111/geb.13121
Subject(s) - ectotherm , ecosystem , ecology , adaptation (eye) , biology , latitude , phylogenetic diversity , thermoregulation , phylogenetic tree , geography , geodesy , neuroscience , biochemistry , gene
Aim In ectotherms, gradients of environmental temperature can regulate metabolism, development and ultimately fitness. The thermal adaptation hypothesis assumes that thermoregulation is costly and predicts that more thermally variable environments favour organisms with wider thermal ranges and thermal limits (i.e., critical thermal minima and maxima, CT min and CT max ) which track environmental temperatures. We test the thermal adaptation hypothesis at two biological levels of organization, the community and species level. Location Continental USA. Time period May–August 2016 and May–August 2017. Major taxa studied Ants (Hymenoptera:Formicidae). Methods We used ramping assays to measure CT max and CT min for 132 species of North American ants across 31 communities spanning 15.7° of latitude. Results Ants were cold tolerant in cooler environments particularly at the community level where CT min was positively correlated with the maximum monthly temperature (CT min = 0.24T max − 0.4; R 2 = .39, p < .001). In contrast, most ant communities included some highly thermophilic species, with the result that CT max did not covary with environmental temperature means or extremes. Consequently, we found no evidence that thermally variable environments supported ant communities with broader thermal ranges. We found a strong phylogenetic signal in CT max but not CT min . Species level responses paralleled community data, where maximum monthly temperatures positively correlated with species CT min but not CT max , which was significantly lower in subterranean species. Main conclusions Our results suggest a large fraction of continental trait diversity in CT max and CT min can be found in a given ant community, with species with high CT max widely distributed regardless of environmental temperature. Species level analyses found the importance of local microclimate and seasonality in explaining thermal tolerances. Frequent invariance in CT max of insects at a large scale might be caused by (a) local adaptations to a site's microclimates and (b) species acclimation potential, both of which cannot be accounted for with mean annual temperatures.