Preferred temperatures of Tarentola mauritanica in spring Miguel A. Carretero CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, Campus Agrário de Vairão, 4485-661 Vairão, Portugal. E-mail: carretero@mail.icav.up.pt Submitted on 2007, 28th August; revised on 2007, 26th October; accepted 2008, 30th January. Abstract. Variation of the preferred temperatures (Tp) by the Moorish gecko (Taren- tola mauritanica) in spring was analysed in a population from NE Iberia. Ten adult specimens were exposed to a thermal gradient and Tp was measured at seven time intervals between 16 and 24 h. Tp values were low (23.44 ± 0.61 ºC, 20.7-26.9 ºC, mean ± SE, range) but geckoes gradually increased Tps between late afternoon and early evening. Surprisingly, mean, maximum and minimum Tps inversely correlated with the body size (SVL), but the results of the analyses remained after size correc- tion. Compared to a previous study carried out in summer, Tps found here were much lower but diel variation persisted. Such patterns are more similar to other noc- turnal or crepuscular geckonids rather than to the well-studied diurnal lacertids liv- ing in the same sites. Specifically, Tp seems to be more plastic and the relationships with body size are opposite. Possible adaptive explanations and guidelines for further work are suggested. Keywords. Preferred temperatures, thermal ecology, Tarentola mauritanica, Gekkonidae. INTRODUCTION In the framework of the lizard studies on thermal ecology, preferred body temper- ature in the absence of thermoregulatory constraints (Tp) constitutes an important trait because it correlates with several physiological optima (Huey and Bennet, 1987; Bauwens et al., 1995; Anguilletta et al., 2002). Nevertheless, Tp may change at both evolutionary and individual scales. On one hand, Tp may shift evolutionarily to approach the dominant environmental temperatures but the rate of such adaptive response varies between phy- logenetic lineages (Hertz et al., 1983; Bennet and John-Alder, 1986; Christian and Weav- ers, 1996; Labra, 1998; Castilla et al., 1999). On the other hand, individual lizards are also able to adapt their Tp in response to temporal variation within their life such as daily and seasonal changes, reproductive condition and feeding status (i.e., Van Damme et al., 1986; Castilla et al., 1999; Brown and Griffin, 2003; Carretero et al., 2005, 2006). Acta Herpetologica 3(1): 57-64, 2008 ISSN 1827-9643 (online) © 2008 Firenze University Press 58 M.A. Carretero Whereas most of the literature on this topic focuses on diurnal lizards, less attention has being paid to nocturnal species. Nevertheless, several studies carried out on crepus- cular or nocturnal geckonids indicate that Tp within the species level is less rigid than in diurnal lizards (Brown, 1996; Rock et al., 2000). Moreover, individual geckos may also change their Tp throughout the day, seasonally or due to pregnancy (Refinetti and Sus- alka, 1997; Zari, 1999; Rock et al., 2000, 2002; Anguilletta et al., 2002; Hare et al., 2002) although patterns are not common for all the species (Anguilletta and Werner, 1998). Geckoes inhabiting temperate regions are of special interest because they must face stronger thermal constraints than those living in tropical habitats (Hitchcock and McBray- er, 2006). Whereas the lizard fauna of the northern side of the Mediterranean Basin is dominated by lacertids, only four geckonid species, all restricted to the warmer areas, are known to the region (Arnold and Ovenden, 2002). The Moorish gecko, Tarentola mau- ritanica is the most common one in the Western Mediterranean (Martínez-Rica, 1997). Although it is found on both sides of Gibraltar Strait, recent phylogeographic evidence (Harris et al., 2004a, b) suggests that the species has colonised Europe only recently after the Glaciations. The Moorish gecko is a medium-sized species (45-85 mm, SVL), mainly occupying natural and artificial vertical surfaces, displaying both diurnal and nocturnal activity and undergoing a winter diapause in the most continental localities (Salvador, 2002; Guarino and Picariello, 2006). Previously, the diel variation of Tp in this species was analysed in summer (when geckoes were already involved in reproduction) in a continen- tal population from Central Spain (Gil et al., 1994). The aim of this study was to analyse the intraspecific variation of Tp in a population of this species living in milder conditions with full activity but not involved in reproduction. MATERIAL AND METHODS A total of ten adult T. mauritanica were collected in a thermomediterranean site from NE Iberia (Bellaterra, Cerdanyola del Vallès, UTM 31T DF2395, 150 m altitude) in late April 2000. Ani- mals were not sexed because reliable sexing tools (Atzori et al., 2007) were not currently available. However, in this period of the year, Moorish geckoes were not still involved in reproductive activi- ties and females should not be pregnant (pers. obs.; Picariello et al., 1989). Geckoes were kept in individual 0.5×0.4×0.3 m housing terraria during less than one week with food (Drosophila flies and Acheta domestica crickets) and water provided ad libitum and then released back at the site of capture after the experiments. Specimens were measured (snout-vent length, SVL) to the nearest 0.05 mm with a digital calliper. Subsequently, they were individually exposed to a thermal gradient (~15-45 ºC, 0.5×0.5×1.5 m length experimental terrarium) produced by a 100 W reflector bulb fixed 15 cm above the substrate and maintaining natural photoperiod. Tp was measured with k-termocouple digital thermometer (Digitron 3208K, accuracy 0.01 ºC) by inserting a probe in the cloaca. Body temperatures were recorded during a single day at seven con- secutive intervals (Fig. 1, Table 1) between 16 and 24 hours (local time, GMT) when the activity of the species in this season peaks in the field (Martínez-Rica, 1974). In order to minimise ther- mal shifts due to stress or contact with the researcher’s hand, no more than 10 seconds mediated between the capture of the gecko in the terrarium and the temperature measurement. Values of Tp were not transformed since distributions did not deviate from normality (Komogorov-Smirnov tests, P > 0.05 in all cases), were homoscedastic (univariate Levene tests and multivariate Box M, P > 0.05) and variances and means were uncorrelated. Since measurements 59Preferred temperatures of Tarentola mauritanica in spring were repeated for the same individual for each interval, an Analysis of Variance for Repeated Meas- ures (rmANOVA) was performed with time as the only independent factor. Sphericity assumption was tested prior to the analyses and subsequent corrections were performed in case that assumption was violated (Statsoft, 2006). RESULTS One of the individuals (no. 4, SVL: 73.1 mm) showed an abnormal behaviour, remain- ing motionless next to the bulb for three hours. Because of that, this experiment was inter- rupted at 21:00 and the specimen was excluded from all the analyses. The Tps recorded for this individual were 25.0 ºC (18:00), 25.90 ºC (19:00), 28.0 ºC (20:00) and 28.70 ºC (21:00). For the remaining nine animals, which were normally active, the Tp values recorded are shown in Table 1, grouped by individual and time interval. The rmANOVA detected a sig- nificant increase in Tp throughout the monitoring time (Fig. 1, Table 2). In fact, the main difference was detected between the measures before sunset, which increased gradually, and those after sunset, which were relatively uniform (Fig. 2). Fig. 1. Temporal variation of the preferred temperatures (Tp) of T. mauritanica. The arrow points the sun- set. Distinctive time measures according to Scheffé post-hoc comparisons (P < 0.05) following a significant rmANOVA (Table 2) are indicated in the ordinates. 60 M.A. Carretero Surprisingly, Tp (mean, maximum and minimum of all measures of each individual) was also negatively correlated with body size (Fig. 2). Because of this, the rmANOVA was repeated using the residuals of the Tp against SVL, but results remained identical (Table 2). Table 1. Group n mean SE min. max. Time 18:00 9 22.32 0.52 20.7 25.3 19:00 9 22.64 0.56 21.2 25.8 20:00 9 23.11 0.59 21.3 26.2 21:00 9 23.17 0.56 21.6 26.2 22:00 9 23.38 0.56 21.6 26.9 23:00 9 23.34 0.53 21.5 26.7 24:00 9 23.40 0.52 21.5 26.6 Individual 1 7 21.56 0.11 21.2 21.9 2 7 22.47 0.31 21.7 24.2 3 7 24.39 0.34 23.1 25.4 5 7 22.61 0.33 21.4 23.4 6 7 23.11 0.22 22.1 23.8 7 7 23.90 0.22 23.2 24.7 8 7 26.24 0.21 25.3 26.9 9 7 21.34 0.12 20.7 21.6 10 7 21.84 0.17 21.2 22.4 total* 9 23.05 0.52 21.3 26.2 * calculated over the individual means of the seven time intervals Table 2. rmANOVA Tp F df P time (R) 5.96 6, 48 0.0001 Mauchley Sphericity test, χ2 43.52 20 0.002 Greenhouse-Geisser epsilon 0.04 Hunyh-Feldt epsilon 0.05 rmANOVA Tp (SVL residual) F df P time (R) 5.96 6, 48 0.0001 61Preferred temperatures of Tarentola mauritanica in spring DISCUSSION The temperatures selected by Tarentola mauritanica in the thermogradient corre- sponded to those typical in other crepuscular geckos in the temperate region. Thus, Tp values were lower that those of the diurnal lacertid Podarcis (hispanica) liolepis, living syn- topically in the same locality and time (Carretero et al., 2006) and other Mediterranean lacertids (Bauwens et al., 1995), but still higher that the activity temperatures found in nature (per. obs.). Moreover, Tps were also much lower than those selected by the con- tinental population in summer (31.56 ºC on average, Gil et al., 1994). Because there is minimal genetic variation between both populations (Harris et al., 2004a, b) and no inter- populational variation in Tps has been recorded in other Tarentola species (Brown, 1996), phylogenetic shift is considered negligible in this case. The lab methodologies between this study and that by Gil et al. (1994) were very similar. Once comparativeness between both works is granted, differences in Tp found are to be attributed to changes in body condi- tion and/or reproductive status. Coastal specimens analysed in spring here could be still in low nutritional condition and select for low temperatures (Brown and Griffin, 2003), whereas continental specimens analysed in summer should have higher fat reserves, but be involved in reproductive activities. Authors did not provide information on the repro- ductive status of the specimens or on female pregnancy. However, in other temperate geckonids, pregnant females are known to select for higher temperatures than non-preg- Fig. 2. Significant relationships between preferred temperatures (mean, maximum and minimum Tp) and body size (SVL) in T. mauritanica. 62 M.A. Carretero nant females and males (Rock et al., 2000; Hitchcock and McBrayer, 2006). Nevertheless, seasonal acclimatisation also needs to be considered (Zari, 1999). Whatever the case, the differences between seasons (or reproductive classes) greatly exceed those found in Medi- terranean lacertids (Carretero et al., 2006). Huey et al. (1989) suggested that the thermal traits of geckonids are more associat- ed to the temperatures of diurnal shelters than to those of the microhabitats of noctur- nal activity. The increase of Tp during the final part of the day found here seems to cor- respond to the gradual selection of warmer microhabitats in the wild when getting dark (Martínez-Rica, 1974), in order to keep longer foraging activity after sunset (Anguilletta et al., 1999). A similar pattern (but a higher level) was also recorded for the continental population in summer (Gil et al., 1994). On the other hand, to our knowledge, this is the first evidence of an inverse relation- ship between Tp and body size in geckonids. Because of the strict protocol followed here, such differences cannot be attributed to a methodological artefact. In fact, in a previ- ous study on the lacertid Podarcis (hispanica) liolepis, similar in size and sympatric with T. mauritanica, the correlation between Tp and body size was positive (Carretero et al., 2006). Usually, small geckos tend to select for similar (Anguilletta et al., 1999) or lower (Hitchcock and McBrayer, 2006) temperatures than large ones. Different causes have been invoked to explain this pattern including poorer body condition, different forag- ing and growth rates and avoidance of aggression by large individuals (Hitchcock and McBrayer, 2006). The opposite pattern found here is tentatively interpreted as the result of the monopolisation by bigger animals of the warmer refuges, which would be of higher thermal quality in spring due to moderate diurnal temperatures and restricted crepuscu- lar activity. Although the territoriality and interspecific aggressions in this species in not under question (Salvador, 2002), this hypothesis needs experimental testing with speci- mens of different sizes in different seasons. In summary, results indicate that T. mauritanica displays high plasticity in preferred temperatures according to the diel and seasonal variation of its thermal environment and also probably modulated by interspecific interactions and reproductive requirements. ACKNOWLEDGEMENTS I wish to thank Anna Soler and Laia Rocavert who helped me in the lab work. Thanks are also due to X. Espadaler (UAB, Bellatera) for logistic support.The final part of this research was funded by the projects POCI/BIA-BDE/55865/2004 and POCI/BIA-BDE/56931/2004 and M.A.C. held the post-doctoral contract SFRH/BPD/27025/2006, all from Fundação para a Ciência e a Tec- nologia, FCT (Portugal). Collecting permits were provided by the Departament de Medi Ambient of the Generalitat de Catalunya (Spain). 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