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Journal of Thermal Biology ] (]]]]) ]]]–]]] 1 Contents lists available at ScienceDirect 3 Journal of Thermal Biology 5 journal homepage: www.elsevier.com/locate/jtherbio 7 9 11 Effect of altitude on thermal responses of Liolaemus pictus argentinus 13 in Argentina 15 Joel Gutie´rrez a,n, John D. Krenz b, Nora R. Ibarguengoytı¨ ´a a,c a 17 Departamento de Zoologı´a del Centro Regional Universitario Bariloche, Unidad Postal Universidad Nacional Del Comahue, Quintral 1250, San Carlos de Bariloche, Rı´o Negro 8400, Argentina b Department of Biological Sciences, Minnesota State University, Mankato, MN 56001, USA 19 c INIBIOMA-CONICET, Universidad Nacional Del Comahue, Quintral 1250, San Carlos de Bariloche, Rı´o Negro 8400, Argentina 21 article info abstract 23 Article history: Reptiles that live in cooler environments hibernate longer and, when active, limit daily activity times, 25 Received 12 April 2010 allocate more time and energy toward thermoregulation, and consequently experience life-history Accepted 6 July 2010 constraints such as reduced fecundity and supra-annual reproductive cycles. This pattern becomes 27 more extreme with increasing latitude and altitude. We compared the thermal biology of two Keywords: populations of Liolaemus pictus argentinus living at two altitudes (771 and 1700 m asl). Environ- 29 Lizards mental, microenvironmental, and operative temperatures were studied in order to describe the capture Thermoregulation sites, sources of heat, and availability of microenvironments appropriate for thermoregulation. The Cold climate body temperatures of L. p. argentinus at capture (Tb) and the preferred temperatures in the laboratory 31 Liolaemidae (Tp) were recorded and integrated with operative temperatures to calculate the effectiveness of thermoregulation. The high-altitude population was found to have a lower mean T (29 1C compared 33 b with 33 1C), while the Tp values for both populations were similar (36.7 1C). The analysis of operative temperatures and Tb in relation to Tp showed that L. p. argentinus behaves as a moderate 35 thermoregulator at high altitude and as a poor thermoregulator at the low-altitude site probably due in part to the avoidance of predation risk. 37 & 2010 Published by Elsevier Ltd. 67 39 69 41 71 1. Introduction sunny patches when they achieve temperatures that are close to maximal body temperatures and are inactive at mid-day (Hertz 43 73 Temperature, especially in ectotherms, plays a fundamental et al., 1983; Sinervo et al., 2010). Not only are lizard body temperatures (T ) lower at higher altitudes and latitudes, but also 45 role in determining life-history patterns because of its influence b 75 on the rate of metabolism and bioenergetics. Environmental they are less variable (Hertz et al., 1983). In the genus Anolis, many attributes of thermal physiology differ markedly among 47 heterogeneity creates a variety of microclimates and ectotherms 77 typically move between microhabitats at appropriate times to closely related species and vary in concert with environmental temperatures (Hertz et al., 1983). Species differences have been 49 thermoregulate. Their success often depends on the availability of 79 suitable thermal microclimates (Smith and Ballinger, 2001), observed in the mean Tb and preferred body temperature (as determined using a thermal gradient in the laboratory), range of 51 which, if available, allow ectotherms such as lizards to attain 81 higher body temperatures and consequently higher rates of activity temperature, and critical thermal maxima. For example, Anolis cristatellus from Puerto Rico actively thermoregulates in 53 metabolism, locomotion, and digestion, resulting in more energy 83 for maintenance and production (Shine, 2004). open environments, but passively loses or gains heat in shaded environments such as a closed-canopy forest (Hertz et al 1993). In 55 Many species of lizards exhibit differences in thermoregula- 85 tory behaviors at different altitudes because of differences in the contrast, in low-insolation environments, the possibility of active thermoregulation is virtually eliminated as shown for the 57 thermal environment (Adolph, 1990; Adolph and Porter, 1993). 87 For example, lizards that inhabit cold mountain environments Australian dragon, Hypsilurus spinipes, and the lizard Xenosaurus newmanorum (Lemos-Espinal et al., 1998). In other cases, lizards 59 bask for longer periods and are less active than lizards at lower 89 elevations. In contrast, lizards in warmer climates typically avoid thermoregulate nearly all year (e.g., Podarcis melisellensis and Podarcis muralis; Smith and Ballinger, 2001. In addition, micro- 61 91 environmental variation affects the activity regime of Sceloporus n merriami populations along altitudinal gradients (Smith and 63 Q1 Corresponding author. 93 E-mail address: [email protected] (J. Gutie´rrez). Ballinger, 2001), and of species such as pristidactylus torquatus 95 65 0306-4565/$ - see front matter & 2010 Published by Elsevier Ltd. doi:10.1016/j.jtherbio.2010.07.001 Please cite this article as: Gutie´rrez, J., et al., Effect of altitude on thermal responses of Liolaemus pictus argentinus in Argentina. J. Thermal Biol. (2010), doi:10.1016/j.jtherbio.2010.07.001 2 J. Gutie´rrez et al. / Journal of Thermal Biology ] (]]]]) ]]]–]]] 1 and pristidactylus volcanensis in Chile that inhabit the closed- 2.2. Estimation of preferred body temperatures 67 canopy Nothofagus forest versus open-canopy forests, respectively 3 (Labra and Rosenmann, 1992). Body temperature preference experiments were conducted the 69 Liolaemus pictus argentinus (Liolaemidae) is a viviparous and day after capture. Lizards were placed individually in open-top 5 insectivorous species with a wide distribution in the Patagonian terraria (200 Â 45 Â 18 cm3) each with a sand floor and a thermal 71 Andes of Neuque´n, Rı´o Negro, and Chubut provinces of Argentina gradient produced by a line of four infra-red lamps overhead (one 7 (39–43 1S and 520–1600 m asl (Donoso-Barros, 1966; Cei, 1986; 250 W, two 150 W, and one 100 W). The lamps were adjusted to 73 Scolaro, 2005)). Previous studies of L. p. argentinus different heights to make a linear substratum gradient from 9 (Ibarguengoytı¨ ´a and Cussac, 2002), Liolaemus elongates, and 15–69 1C. Lizard body temperatures were measured every 10 min 75 Phymaturus tenebrosus (Ibarguengoytı¨ ´a, 2005; Ibarguengoytı¨ ´a for 5 h using ultra thin (1 mm) catheter thermocouples located 11 et al., 2008) suggest that environments characterized by low approximately 10 mm inside the cloaca and fastened to the base 77 temperatures throughout the year and short activity seasons limit of the lizard’s tail to keep the thermocouple in position during the 13 the opportunities for thermoregulation and in turn influence experiment (TES 1302 thermometer, TES Electrical Electronic 79 several life-history traits. These species are predominantly Corp., Taipei, Taiwan, 70.03 1C). All measurements were taken so 15 heliothermal and at low altitude (Ibarguengoytı¨ ´a and Cussac, as to minimize interference with their normal activities. The 81 2002) a mean Tb of 33.2 1C was observed, which is similar to that duration of the experiments corresponded to previous trials that 17 of other liolaemids (32.5 1C, N¼45 lizards; Medina et al., 2009). measured the amount of time required for Liolaemus bibronii 83 Herein we report differences in thermal physiology in L. p. (Medina et al., 2009), Liolaemus pictus (Gutie´rrez, 2009), 19 argentinus between high and low altitude populations in close and several other liolaemids (Liolaemus lineomaculatus, Liolaemus 85 proximity. boulengeri, L. elongatus, and Liolaemus fitzingeri; Ibarguengoytı¨ ´a, 21 unpublished data) to reach their preferred temperature 87 asymptote. 23 We estimated the mean and range of the preferred body 89 temperature (Tp) for each individual. The set-point range (Tset), 25 2. Materials and methods considered as the temperatures within the interquartile range of 91 the observations, was also noted because earlier studies show 27 2.1. Study areas and field methods neurophysiological evidence that ectotherms regulate between 93 upper and lower set-point temperatures rather than around a 29 The two field sites in northwestern Patagonia, Argentina, are Cerro single Tb (Barber and Crawford, 1977; Firth and Turner, 1982). The 95 Challhuaco (41115057.900Sand71117057.400 W; 1615–1769 m asl) and interquartile range represents the natural settings caused by the 31 Melipal Beach on lake Nahuel Huapi (41107041.5300Sand711 hypothalamic thermostat in lizards and fishes (Barber and 97 20044.8700W, 771 m asl), both near the city of San Carlos de Bariloche Crawford, 1977; Firth and Turner, 1982). In order to measure 33 in Rı´o Negro Province. Lizards (N¼30) were captured by loop or hand the average extent to which L. p. argentinus experienced Tb values 99 at high altitude in December 2005, in January, April, and December outside the set-point range, the sum of absolute values of the 35 2006, and in February 2007. At low altitude, 33 lizards were captured deviations of Tb from Tset of each individual was calculated 101 in February and March of 2006 and 2007.