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Summer diet of Podarcis milensis, Podarcis gaigeae and Podarcis erhardii (Sauria: Lacertidae)
... Podarcis erhardii, the Aegean Wall Lizard (Figure 1), is a medium-sized (50-75 mm adult snout-vent length, [33]) mesopredator that is widely distributed across the Aegean Sea archipelagos and can be found living on the largest islands and even small rocky outcropping islets [34,35]. The species is an invertebrate generalist [33] consuming snails and a wide range of arthropods, including larvae [29,36], while cannibalism has also been reported [37]. In contrast to several other Podarcis species, insular P. erhardii populations are not known for shifting their diet consistently to plant material [36]. ...
... The species is an invertebrate generalist [33] consuming snails and a wide range of arthropods, including larvae [29,36], while cannibalism has also been reported [37]. In contrast to several other Podarcis species, insular P. erhardii populations are not known for shifting their diet consistently to plant material [36]. However, frugivory and limited herbivory have previously been observed among small-island populations [29,38]. ...
... The latter hosts the most diverse and complex vegetation of all the islets. This higher plant abundance may have also played a role in the more frequent consumption of plant material [36,68]. Herbivory represents a consistent trend among islet Podarcis lizards [15,19,69,70]. ...
Resource-limited environments may drive the rapid evolution of phenotypic traits and ecological preferences optimizing the exploitation of resources. Very small islands are often characterized by reduced food availability, seasonal fluctuations in resources and strong unpredictability. These features may drive the evolution of phenotypic traits such as high bite forces, allowing animals to exploit a wider variety of the available resources. They may also lead to more generalist dietary patterns in response to food scarcity. However, the lack of predators and competitors on such small islands often also leads to high densities and the evolution of strong sexual dimorphism, which may also drive the evolution of bite force. Here, we take advantage of a unique replicated introduction experiment to test whether lizards introduced into very small islands alter their feeding ecology and use different resources, resulting in the evolution of a large body size, large head size and large bite forces. Our results show that three years after their introduction, the island lizards were larger and had greater bite forces and more pronounced sexual dimorphism. However, the diets were only marginally different between animals from the source population on a very large nearby island and those on the islets. Moreover, distinct differences in diet between animals on the different islets were observed, suggesting that the local environment is a strong driver of resource use. Overall, lizards with absolutely and relatively (adjusted for body size) large bite forces did eat larger and harder prey. Taken together, our data suggest that intraspecific competition is an important driver of the rapid evolution of bite force, which may allow these lizards to exploit the scarce and fluctuating resources on the islets. Whether or not lizards will evolve to include other types of food such as plants in their diet, facilitated by their large bite forces, remains to be explored in future studies.
... They are particularly common in areas that provide refugia in the form of broken-up terrain and anthropogenic structures such as dry-stone walls and terraces (Brock et al., 2015b). P. erhardii consume a broad range of arthropods (Arnold, 1987), with a particular emphasis on Coleoptera, Orthoptera, and soft-bodied larvae (Adamopoulou, Valakos & Pafilis 1999). Additional secondary food items include snails (Adamopoulou, Valakos & Pafilis 1999) and even fruit (Brock, Donihue, & Pafilis, 2014), although the species is not known to consume nectar or vegetable matter like other island taxa. ...
... P. erhardii consume a broad range of arthropods (Arnold, 1987), with a particular emphasis on Coleoptera, Orthoptera, and soft-bodied larvae (Adamopoulou, Valakos & Pafilis 1999). Additional secondary food items include snails (Adamopoulou, Valakos & Pafilis 1999) and even fruit (Brock, Donihue, & Pafilis, 2014), although the species is not known to consume nectar or vegetable matter like other island taxa. Recent observations suggest that the species displays at least occasionally cannibalistic tendencies (Adamopoulou, Valakos & Pafilis, 1999). ...
... Additional secondary food items include snails (Adamopoulou, Valakos & Pafilis 1999) and even fruit (Brock, Donihue, & Pafilis, 2014), although the species is not known to consume nectar or vegetable matter like other island taxa. Recent observations suggest that the species displays at least occasionally cannibalistic tendencies (Adamopoulou, Valakos & Pafilis, 1999). ...
Reproductive investment, including the average number of offspring produced by an organism, is one of the fundamental characteristics of a species. Among other things, it predicts a species’ resilience to environmental disruption: taxa that produce more offspring are able to recover more quickly from environmental perturbations and survive long-term environmental change. Despite the clear importance of this trait, ecologists do not have a good understanding of the primary drivers shaping the reproductive investment of each species. To answer this question, I compare the reproductive efforts of numerous island populations of the Aegean Wall Lizard (Podarcis erhardii), which differ in multiple key environmental characteristics. I test three hypotheses, namely that reproductive investment (measured as clutch size, clutch volume and egg volume) is: 1) positively associated with predation risk [‘Predation Risk Hypothesis’]; 2) positively associated with the presence of reliable vegetation cover that provides shelter [‘Gravid Female Protection Hypothesis’], and 3) limited by (and hence positively correlated with) food availability [‘Food Limitation Hypothesis’]. Although field data are consistent with all three hypotheses, statistical analysis shows strong support for the Predation Risk Hypothesis. The result not only shed light on which fundamental forces shape reproductive investment in island vertebrates, but can also help set conservation priorities by identifying the most sensitive populations because reduced reproductive ability can be predicted based on easily quantifiable island characteristics (number of sympatric predator species).
... In this study, we quantify and compare cognitive abilities of Aegean wall lizards (Podarcis erhardii Bedriaga 1882) from a mainland and island habitat. Compared to the mainland, arthropod abundance and diversity on islands is often poor (Janzen, 1973;Andrews, 1979;Olesen & Valido, 2003) and more subject to seasonal variation (Karamaouna, 1987;Parashi, 1988;Trihas & Legakis, 1991;Adamopoulou et al., 1999). In accordance, many island lizards in the Mediterranean exhibit dietary versatility, switching to alternative food resources such as plants and ants to survive unfavourable periods (e.g., extremely dry summers with food scarcity) (Pérez-Mellado & Corti, 1993;Adamopoulou et al., 1999;Lo Cascio et al., 2001;Rodríguez et al., 2008;Sagonas et al., 2015). ...
... Compared to the mainland, arthropod abundance and diversity on islands is often poor (Janzen, 1973;Andrews, 1979;Olesen & Valido, 2003) and more subject to seasonal variation (Karamaouna, 1987;Parashi, 1988;Trihas & Legakis, 1991;Adamopoulou et al., 1999). In accordance, many island lizards in the Mediterranean exhibit dietary versatility, switching to alternative food resources such as plants and ants to survive unfavourable periods (e.g., extremely dry summers with food scarcity) (Pérez-Mellado & Corti, 1993;Adamopoulou et al., 1999;Lo Cascio et al., 2001;Rodríguez et al., 2008;Sagonas et al., 2015). On the basis of the CBH, we expect that environmental variability on the island will select for behavioural flexibility and hence increased cognitive capacities. ...
... Although we are unable to present data on food availability, we clearly demonstrated that Naxos experiences stronger seasonal variation in NDVI and precipitation, both of which are important indicators of resource availability. This seems to be in line with the strong seasonal fluctuations in arthropod abundances, characterized by a sharp drop during dry summers, typically observed on Mediterranean islands (Karamaouna, 1987;Parashi, 1988;Trihas & Legakis, 1991;Adamopoulou et al., 1999;Carpaneto & Fattorini, 2001;Sagonas et al., 2015;Mamou et al., 2019). In such a variable habitat with frequent periods of food scarcity the CBH predicts higher behavioural flexibility, while the EBH expects the opposite. ...
Harsh and variable environments have been hypothesized to both drive and constrain the evolution towards higher cognitive abilities and behavioural flexibility. In this study, we compared the cognitive abilities of island and mainland Aegean wall lizards ( Podarcis erhardii ), which were expected to live in respectively a more variable and a more stable habitat. We used four proxies of behavioural flexibility: a neophobia assay, a problem-solving test and a spatial + reversal learning task. Surprisingly, the two populations did not differ in neophobia or problem-solving. Insular lizards, however, outperformed mainland conspecifics in an initial spatial learning task, but were less successful during the subsequent reversal learning. Our results thus seem to indicate that the effect of environmental variability on cognition is complex, as it may favour some, but not all aspects of behavioural flexibility.
... The Lacertidae family is the most speciesdiverse lizard family in Europe, and its representatives are widely distributed across the area. Although there have been a number of studies on food preferences and trophic ecology of lacertid lizards, they focus mostly on species from Western Europe and the Mediterranean (Arnold 1987, Adamopoulou et al. 1999, Capula & Luiselli 1994, Carretero & Llorente 1993, Crovetto & Salvidio 2013, while less attention has been directed to Eastern Europe and the non-Mediterranean part of the Balkan Peninsula in particular. Lacertids are opportunistic feeders and are mainly insectivorous (Arnold 1987, Carretero 2004 and references therein) but they also feed on other arthropods, snails, etc. (Castilla et al. 2008, Van der Meer et al. 2010). ...
... Food resources in the study areas were evaluated by pitfall traps for collecting of invertebrates, which is a widely used method in similar studies (e.g., Diaz & Carascal 1993, Hódar et al. 1996, Adamopoulou et al. 1999, Crovetto & Salvidio 2013. Cylindrical plastic containers (9.5 cm wide and 12 cm deep), filled with propylene glycol, were used as pitfall traps. ...
... Our results strongly underline that Z. vivipara feeds mainly on arthropods, like many other lacertids (see Arnold 1987, Adamopoulou et al. 1999. Four arthropod groups, Hemiptera (mostly from the Suborder Auchenorryncha), Araneae, Coleoptera, and Formicidae, composed more than 70% of the consumed preys. ...
Although the Viviparous lizard (Zootoca vivipara) is one of the most successful lizard species and is widespread across Eurasia, data on its dietary habits are still lacking, especially from the southern part of its range. In order to shed light on its diet, we conducted а study in three high mountains in Bulgaria, which represent separate "patches" from the range of Z. vivipara in the country. To investigate the food preferences, we adopted a non-invasive method using faecal samples and a total of 290 faecal samples that could be assigned to individual specimens with determined age and sex were collected. A total of 19 prey categories were detected and the number of categories per each study site varied between 16 and 18, which indicates opportunistic feeding habits. The most preferred prey types were Auchenorrhyncha (Order Hemiptera) and Araneae, while Formicidae and Opilones, abundant in the field, were avoided. Two physical characteristics of the prey, hardness and evasiveness, were analysed. In respect to hardness, Z. vivipara choose more often hard prey, and in respect to evasiveness, sedentary prey was consumed more often, hence we could suggest that Z. vivipara is an active forager. Statistically significant differences between immatures and adults were found as adults showed more diverse diet. No such differences between sexes were detected. Two cases of (partial) cannibalism and many cases of keratophagy (in 9% of the faecal pellets) were detected.
... Podarcis erhardii are often described as insectivores that feed mainly on coleopterans, orthopterans, and arachnids (Valakos et al. 1997;Valakos et al. 2008). Although some seasonal fluctuations of diet are present, during the summer and spring seasons, Coleoptera have been observed to be the most common prey for P. erhardii (Adamopoulou et al. 1999). However, P. erhardii from islands have been observed consuming food items such as vegetation and marine life (Brock et al. 2014). ...
... On the other hand, P. erhardii reaches some of the highest recorded densities on Andros (Brock et al. , 2022Donihue et al. 2015), which may induce competition for food. Since arthropods, such as Coleoptera, have been observed to be the most common prey for P. erhardii during this season, this consumption is unusual (Adamopoulou et al. 1999). Although the motives for this consumption are still unclear, observations of food items outside of the coleopteran, orthopteran, and arachnid dietary preferences of P. erhardii are previously documented and tend to happen on islands (Brock et al. 2014;Donihue et al. 2015;Madden and Brock 2018). ...
Podarcis wall lizards mainly feed on coleopterans, orthopterans, arachnids, and other small invertebrates. However, Aegean wall lizards, Podarcis erhardii , are widely distributed across Aegean islands and are increasingly observed eating non-traditional food items ranging from plant material to conspecific eggs and body parts. Here, we report the first documented case of P. erhardii consuming a large centipede, Scolopendra cingulata . The predator-prey relationship between these species has appeared to go both ways and may intensify on islands.
... It can be considered an ecological generalist, as demonstrated by its broad habitat use (e.g. Mediterranean scrublands, open sand dunes, urban habitats; Lymberakis et al., 2018;Valakos et al., 2008) and its dietary flexibility (arthropods, snails, eggs, fruits and occasionally conspecifics; Adamopoulou et al., 1999;Brock et al., 2014;I. Madden & Brock, 2018). ...
... Nevertheless, the low genetic variation in our lizards could also result from a genetic bottleneck when the lizards were introduced into our enclosures (Carrete et al., 2017), or it could be a consequence of strong directional selection on explorative behaviour in the past (Boake, 1989;Falconer & Mackay, 1996;Wheelwright et al., 2014). Large seasonal fluctuations in precipitation, and accordingly, arthropod abundances on Naxos (Adamopoulou et al., 1999;De Meester et al., 2021;Karamaouna, 1987;Parashi, 1988) may exert strong selection on explorative behaviour in Aegean wall lizards if it facilitates discovery and acquisition of resources (Bajer et al., 2015;Baxter-Gilbert et al., 2019). However, we did observe negative selection on exploration in a previous sample of lizards from 2018 to 2019, but not in the current sample (De Meester, 2022). ...
Recently, biologists have become increasingly interested in cognitive variation among individuals and how it relates to differences in fitness. However, very few studies so far have studied the long-term repeatability and heritability of cognitive performance in wild animals. This is nevertheless crucial information to fully understand the potential ecological and evolutionary impact of individual variation in cognitive performance. In 2019, we assessed exploration, problem solving and spatial and reversal learning in 66 Aegean wall lizards, Podarcis erhardii, then released them in seminatural enclosures consisting of either simple or complex habitat. One year later, we recaptured and retested the surviving lizards and their offspring to estimate the long-term repeatability and heritability of these behavioural and cognitive characteristics. We found that exploration and spatial learning were moderately repeatable, but reversal learning only marginally and learning flexibility and problem solving not at all. Reversal learning ability declined over time in lizards kept in simple habitat, but not in those kept in complex habitats – suggesting habitat-dependent cognitive plasticity. To our knowledge, this is the first study demonstrating (long-term) consistency in cognitive traits within a nonavian reptile. The combination of modest repeatability and low heritability does suggest that, within our study species, personality and cognitive variation among individuals and populations is mostly moulded by environmental effects.
... The Aegean wall lizard is a medium-sized lacertid lizard, found in a variety of habitats across the Greek mainland and Aegean islands (Valakos et al. 2008;Brock et al. 2015). Its diet mostly consists of arthropods, but occasionally includes snails, eggs, fruits, and even conspecifics (Adamopoulou et al. 1999;Brock et al. 2014;Donihue, 2016;Madden and Brock, 2018). ...
Animals exhibit considerable and consistent among-individual variation in cognitive abilities, even within a population. Recent studies have attempted to address this variation using insights from the field of animal personality. Generally, it is predicted that animals with “faster” personalities (bolder, explorative, and neophilic) should exhibit faster but less flexible learning. However, the empirical evidence for a link between cognitive style and personality is mixed. One possible reason for such conflicting results may be that personality–cognition covariance changes along ecological conditions, a hypothesis that has rarely been investigated so far. In this study, we tested the effect of habitat complexity on multiple aspects of animal personality and cognition, and how this influenced their relationship, in five populations of the Aegean wall lizard (Podarcis erhardii). Overall, lizards from both habitat types did not differ in average levels of personality or cognition, with the exception that lizards from more complex habitats performed better on a spatial learning task. Nevertheless, we found an intricate interplay between ecology, cognition, and personality, as behavioral associations were often habitat- but also year-dependent. In general, behavioral covariance was either independent of habitat, or found exclusively in the simple, open environments. Our results highlight that valuable insights may be gained by taking ecological variation into account while studying the link between personality and cognition.
... erhardii), SVL up to 120 mm, is widely distributed in both insular and mainland Greece and belongs to a distinct phylogenetic group that has been separated from the phylogenetic group of P. milensis (Lymberakis and Poulakakis 2010). Both species, exactly like P. siculus, are diurnal, heliothermic and feed mainly on terrestrial arthropods, predominately insects (Adamopoulou et al. 1999;Adamopoulou and Legakis 2002;Corti 2006). Currently, P. siculus has not yet contacted other congeneric lizards in Athens as it remained restricted to the area that was discovered thanks to the aforementioned eradication project by the Hellenic Herpetological Society. ...
Though biological invasions constitute one of the biggest threats for global biodiversity, our understanding of the mechanisms that enable invasive species to outperform native species is still limited, especially, in terms of behavior. Most available studies have examined behavioral traits which favor invasive species on the later stages of invasion, however, our knowledge on earlier stages, namely, when alien species face novel environments and must exploit new resources, remains obscure. Here, we focus on one crucial behavioral trait, finding food. The Italian wall lizard (Podarcis siculus) has been widely introduced and established viable populations in S. Europe and N. America. We examined whether P. siculus has enhanced exploratory behavior and abilities to find food compared to two native congeneric species with which it may come in contact in the near future, an insular endemic (P. milensis) and a widely distributed lizard (P. erhardii). We performed a Y-maze experiment, in which we varied arm markings in a standard way to prevent learning. Podarcis siculus was more efficient than its congenerics in finding and consuming food. This exploitative superiority was persistent, more frequent and repetitive. Interesting behavioral differences were also detected within the native species. Some P. milensis individuals showed no interest in exploring the maze, while few P. erhardii individuals remained rather indifferent to food even after detecting it. Our results suggest that the invasive P. siculus displays behavioral traits that could provide better opportunities for survival in the new environment and thus facilitate establishment even in the presence of congenerics. This provides further support to the idea that behavior plays a crucial role in animal invasions.
... In the Archipelago, it is the most common lacertid lizard species (Lymberakis et al. 2018). It is mainly an insectivorous species, feeding primarily on coleopterans, orthopterans and arachnids, but expands its diet during the summer months to include ants and fruits (Valakos et al. 1997;Adamopoulou et al. 1999;Brock et al. 2014). Scolopendra cingulata has a widespread distribution that includes northern Africa, western Asia, central and south-eastern Europe and many Mediterranean islands (excluding Sardinia, Corsica and the Balearic Islands) (Simaiakis and Mylonas 2008). ...
Centipedes feed mainly on insects and other invertebrates. However, they may occasionally enhance their diet with small vertebrates. Lizard consumption by centipedes is rather rare. Here, we report an incident of saurophagy by the most common Mediterranean scolopendrid, Scolopendra cingulata, on the Aegean wall lizard, Podarcis erhardii. Island particularities may trigger such behaviours that could be more frequent than previously thought.
Over-water dispersal to small islets is an important eco-evolutionary process. Most often, new arrivals on islets find the environment harsh or mate-less, making their footholds on these islets fleeting. Occasionally, introduced animals are able to survive the strong selection following their arrival, leading to subsequent propagation and, in several famous cases, adaptive radiation. What traits predict that initial survival? We established a replicated island introduction experiment to investigate this process in lizards. In 2014, we introduced 20 Podarcis erhardii lizards to each of five small islets in the Greek Cyclades Islands. We found that the lizards that survived were those with better initial body condition, longer distal portions of their limbs and a greater propensity for jumping. Contrary to our expectations, neither body size nor the strength of the lizards’ bite – two traits positively related to competitive ability, which becomes important later in the colonization process in lizards – predicted survival. This is the first selection study of its kind investigating an experimental introduction of Podarcis, and whether the traits that determined initial survival are important in driving the future evolutionary trajectories of these populations remains to be determined.
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