Ecological Entomology (2017), 42, 758–767 DOI: 10.1111/een.12447 Thermal tolerance and recovery behaviour of Thorectes lusitanicus (Coleoptera, Geotrupidae) BELÉN G A L L E G O, 1,2 JOSÉ R. V E R D Ú, 1 LUIS M. CARRASCAL 2 and J O R G E M. LOBO 2 1 I.U.I. CIBIO, Universidad de Alicante, San Vicente del Raspeig, Spain and 2 Department of Biogeography and Global Change, Museo Nacional de Ciencias Naturales-CSIC, Madrid, Spain Abstract. 1. Population differences in physiological responses are examined in Thorectes lusitanicus, an endemic Iberian dung beetle species, by submitting individuals of different populations to the same experimental and acclimation conditions. 2. An infrared thermography protocol was used, consisting of three assays: start of activity, cold response, and heat response. Individuals of 12 populations were studied and the comparative explanatory capacities of several environmental factors in relation to the observed inter-population differences were examined. 3. The heating rate from chill coma to the beginning of activity was the variable with the highest discrimination power among the studied populations, accounting for 94% of the observed variance. Regarding the heat response, only six of the 16 thermal variables reached signifcance (inter-population differences accounted for 52–74% in these six thermal parameters). 4. From the three considered environmental factors (Mediterranean climate, land cover, and trophic characteristics) only land cover characteristics remain statistically signifcant, affecting the cold response of individuals. 5. Thorectes lusitanicus is a species characterised by a high diversity of thermotoler- ance and recovery traits across populations with a low degree of association with broad environmental factors. Finally, it is suggested that the apterous character of this species could be a determinant factor explaining the high diversity of ecophysiological traits related to thermal stress tolerance and the recovery time. Key words. Infrared thermography, insect physiology, physiological diversity, thermal stress, thermal tolerance, thermoregulation. Introduction Physiological diversity is the variability in physiological traits among animals, plants, and other organisms (Spicer & Gaston, 2009). The existence of this diversity is the foundation of evolutionary physiology, which aims to understand the origin and maintenance of the variety of physiological responses among populations or species inhabiting different environmental conditions (Garland & Adolph, 1991; Schmidt-Nielsen, 1997; Chown, 2001), due to biotic (Nosil et al., 2005) and abiotic factors (Gandon et al., 1998; Rieseberg et al., 1999; Hall, 2005). Among these abiotic factors, environmental temperature has a widespread effect, as it affects almost all biological processes, from molecular kinetics to organismal ftness and Correspondence: Belén Gallego, I.U.I. CIBIO Universidad de Ali- cante, Carretera San Vicente del Raspeig, s/n, 03690, San Vicente del Raspeig, Spain. E-mail: bgp5@alu.ua.es global distribution patterns (Angilletta, 2009; Kingsolver, 2009; Keller & Seehausen, 2012; Ma et al., 2015; Buckley & Huey, 2016). The response to environmental temperature of different pop- ulations may vary as a consequence of phenotypic plasticity (i.e. the same genotype with different phenotypic responses; see West-Eberhard, 1989; Chown & Terblanche, 2006) or because of the existence of ecotypes (i.e. genetically distinct sub-populations restricted to specifc areas and habitats mani- festing specifc tolerance limits to local factors; Turrill, 1946; Lowry, 2012). These responses can also be different under natural conditions (Spicer & Gaston, 2009), but similar after the individuals are subjected to common laboratory conditions (acclimation). This can happen as a consequence of reversible local physiological acclimatisation processes, in which case phenotypic plasticity can play a signifcant role. For example, the dung beetle Canthon humectus hidalgoensis Bates, 1887 exhibits inter- and intra-population variability in its thermal 758 © 2017 The Royal Entomological Society