Ant assemblages have darker and larger members in cold environments

dc.contributor.authorBishop, Tom R.
dc.contributor.authorRobertson, Mark P.
dc.contributor.authorGibb, Heloise
dc.contributor.authorJanse Van Rensburg, Berndt
dc.contributor.authorBraschler, Brigitte
dc.contributor.authorChown, Steven L.
dc.contributor.authorFoord, Stefan H.
dc.contributor.authorMunyai, Thinandavha Caswell
dc.contributor.authorOkey, Iona
dc.contributor.authorTshivhandekano, Pfarelo G.
dc.contributor.authorWerenkraut, Victoria
dc.contributor.authorParr, Catherine Lucy
dc.date.accessioned2017-01-12T07:05:38Z
dc.date.available2017-01-12T07:05:38Z
dc.date.issued2016-12
dc.description.abstractAIM : In ectotherms, the colour of an individual’s cuticle may have important thermoregulatory and protective consequences. In cool environments, ectotherms should be darker, to maximize heat gain, and larger, to minimize heat loss. Dark colours should also predominate under high UV-B conditions because melanin offers protection. We test these predictions in ants (Hymenoptera: Formicidae) across space and through time based on a new, spatially and temporally explicit, global-scale combination of assemblage-level and environmental data. LOCATION : Africa, Australia and South America. METHODS : We sampled ant assemblages (n5274) along 14 elevational transects on three continents. Individual assemblages ranged from 250 to 3000 m a.s.l. (minimum to maximum range in summer temperature of 0.5–35 8C). We used mixed-effects models to explain variation in assemblage cuticle lightness. Explanatory variables were average assemblage body size, temperature and UVB irradiation. Annual temporal changes in lightness were examined for a subset of the data. RESULTS : Assemblages with large average body sizes were darker in colour than those with small body sizes. Assemblages became lighter in colour with increasing temperature, but darkened again at the highest temperatures when there were high levels of UV-B. Through time, temperature and body size explained variation in lightness. Both the spatial and temporal models explained c. 50% of the variation in lightness. MAIN CONCLUSIONS : Our results are consistent with the thermal melanism hypothesis, and demonstrate the importance of considering body size and UVB radiation exposure in explaining the colour of insect cuticle. Crucially, this finding is at the assemblage level. Consequently, the relative abundances and identities of ant species that are present in an assemblage can change in accordance with environmental conditions over elevation, latitude and relatively short time spans. These findings suggest that there are important constraints on how ectotherm assemblages may be able to respond to rapidly changing environmental conditions.en_ZA
dc.description.departmentZoology and Entomologyen_ZA
dc.description.librarianam2016en_ZA
dc.description.sponsorshipThe Mariepskop transect was financially supported by the NRF and 19 Helicopter Squadron at Hoedspruit provided logistical support. T.R.B. was supported by a NERC studentship.en_ZA
dc.description.urihttp://wileyonlinelibrary.com/journal/geben_ZA
dc.identifier.citationBishop, TR, Robertson, MP, Gibb, H, Van Rensburg, BJ, Braschler, B, Chown, SL, Foord, SH, Munyai, TC, Okey, I, Tshivhandekano, PG, Werenkraut, V & Parr, CL 2016, 'Ant assemblages have darker and larger members in cold environments', Global Ecology and Biogeography, vol. 25, no. 12, pp. 1489-1499.en_ZA
dc.identifier.issn1466-822X (print)
dc.identifier.issn1466-8238 (online)
dc.identifier.other10.1111/geb.12516
dc.identifier.urihttp://hdl.handle.net/2263/58490
dc.language.isoenen_ZA
dc.publisherWileyen_ZA
dc.rights© 2016 The Authors. Global Ecology and Biogeography published by John Wiley & Sons Ltd. This is an open access article under the terms of the Creative Commons Attribution License.en_ZA
dc.subjectAssemblage structureen_ZA
dc.subjectColouren_ZA
dc.subjectElevationen_ZA
dc.subjectLatitudeen_ZA
dc.subjectLightnessen_ZA
dc.subjectTemperatureen_ZA
dc.subjectThermal melanismen_ZA
dc.subjectThermoregulationen_ZA
dc.titleAnt assemblages have darker and larger members in cold environmentsen_ZA
dc.typeArticleen_ZA

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