New record of the viviparous lizard Zootoca vivipara (Jacquin, 1787) in Hungary

The lowland populations of the viviparous lizard Zootoca vivipara in the Carpathian Basin occur in cold, marshy relict habitats. In one of the largest wetlands in Hungary, Kis-Balaton, in 2016 its presence was confirmed by catching an individual with a small mammal live-trap. This new record is significant, since the nearest known sites of occurrence are at great distance and it is situated between the lowland viviparous populations of the north-northeast and the oviparous populations of the south (in Croatia).

Social information use for spatial decision in Zootoca vivipara

Movements of individuals are conditioned by information acquisition coming from either personal or social sources. Yet, little is known about the processes used by individuals to make movement decisions when facing multiple sources of social information simultaneously. This study aimed to test experimentally how social information from multiple sources is used to make movement decisions, and whether a contrast in this information allows individuals to orientate in space. We used common lizards (Zootoca vivipara) in a replicated experimental setting: one focal individual received information from two other individuals coming from peripheral environments, before being given the opportunity to relocate in one or another of the peripheral environments. Our analyses revealed that the behavior of informants, their mothers' morphology, as well as the quality of informants' environment, affected movement decisions: the probability to relocate from the focal area increased when informants displayed traits associated with low resources (no food intake, poor maternal condition) or high competition (high activity). The physical condition of individuals also mediated the use of social information about food intake, with a match between resource availability in informants and personal condition. Conversely, spatial orientation was not affected by the contrast of phenotype between informants nor by spatial variability in resource availability. This study highlights that multiple social information sources can be used for movement decisions, likely because these information sources reflect the quality of the surrounding environment (e.g., competition level or resources availability). It also emphasizes that social information use for movement is conditioned by individual phenotype.

Climatic niche differences among Zootoca vivipara clades with different parity modes: implications for the evolution and maintenance of viviparity

Parity mode (oviparity/viviparity) importantly affects the ecology, morphology, physiology, biogeography and evolution of organisms. The main hypotheses explaining the evolution and maintenance of viviparity are based on bioclimatic predictions and also state that the benefits of viviparity arise during the reproductive period. We identify the main climatic variables discriminating between viviparous and oviparous Eurasian common lizard (Zootoca vivipara) occurrence records during the reproductive period and over the entire year.Analyses based on the climates during the reproductive period show that viviparous clades inhabit sites with less variable temperature and precipitation. On the contrary, analyses based on the annual climates show that viviparous clades inhabit sites with more variable temperatures.Results from models using climates during reproduction are in line with the “selfish-mother hypothesis”, which can explain the success of viviparity, the maintenance of the two reproductive modes, and why viviparous individuals cannot colonize sites inhabited by oviparous ones (and vice versa). They suggest that during the reproductive period viviparity has an adaptive advantage over oviparity in less risky habitats thanks to the selfish behaviour of the mothers. Moreover, the results from both analyses stress that hypotheses about the evolution and maintenance of viviparity need to be tested during the reproductive period.

Short-term changes in air humidity and water availability weakly constrain thermoregulation in a dry-skinned ectotherm

Thermoregulation is critical for ectotherms as it allows them to maintain their body temperature close to an optimum for ecological performance. Thermoregulation includes a range of behaviors that aim at regulating body temperature within a range centered around the thermal preference. Thermal preference is typically measured in a thermal gradient in fully-hydrated and post-absorptive animals. Short-term effects of the hydric environment on thermal preferences in such set-ups have been rarely quantified in dry-skinned ectotherms, despite accumulating evidence that dehydration might trade-off with behavioral thermoregulation. Using experiments performed under controlled conditions in climatic chambers, we demonstrate that thermal preferences of a ground-dwelling, actively foraging lizard (Zootoca vivipara) are weakly decreased by a daily restriction in free-standing water availability (less than 0.5°C contrast). The influence of air humidity during the day on thermal preferences depends on time of the day and sex of the lizard, and is generally weaker than those of of free-standing water (less than 1°C contrast). This shows that short-term dehydration can influence, albeit weakly, thermal preferences under some circumstances in this species. Environmental humidity conditions are important methodological factors to consider in the analysis of thermal preferences.

Additive effects of temperature and water availability on pregnancy in a viviparous lizard

ABSTRACTOne of the greatest current threats to biodiversity is climate change. However, understanding of organismal responses to fluctuations in temperature and water availability is currently lacking, especially during fundamental life-history stages such as reproduction. To further explore how temperature and water availability impact maternal physiology and reproductive output, we used the viviparous form of the European common lizard (Zootoca vivipara) in a two-by-two factorial design manipulating both hydric and thermal conditions, for the first time. We collected blood samples and morphological measurements during early pregnancy and post-parturition to investigate how water availability, temperature and a combination of the two influence maternal phenology, morphology, physiology and reproductive output. We observed that dehydration during gestation negatively affects maternal physiological condition (lower mass gain, higher tail reserve mobilization) but has little effect on reproductive output. These effects are mainly additive to temperature regimes, with a proportional increase in maternal costs in warmer environments. Our study demonstrates the importance of considering combined effects of water and temperature when investigating organismal responses to climate changes, especially during periods crucial for species survival such as reproduction.

Chromosome-Level Assembly of the Common Lizard (Zootoca vivipara) Genome

Squamate reptiles exhibit high variation in their phenotypic traits and geographical distributions and are therefore fascinating taxa for evolutionary and ecological research. However, genomic resources are very limited for this group of species, consequently inhibiting research efforts. To address this gap, we assembled a high-quality genome of the common lizard, Zootoca vivipara (Lacertidae), using a combination of high coverage Illumina (shotgun and mate-pair) and PacBio sequencing data, coupled with RNAseq data and genetic linkage map generation. The 1.46-Gb genome assembly has a scaffold N50 of 11.52 Mb with N50 contig size of 220.4 kb and only 2.96% gaps. A BUSCO analysis indicates that 97.7% of the single-copy Tetrapoda orthologs were recovered in the assembly. In total, 19,829 gene models were annotated to the genome using a combination of ab initio and homology-based methods. To improve the chromosome-level assembly, we generated a high-density linkage map from wild-caught families and developed a novel analytical pipeline to accommodate multiple paternity and unknown father genotypes. We successfully anchored and oriented almost 90% of the genome on 19 linkage groups. This annotated and oriented chromosome-level reference genome represents a valuable resource to facilitate evolutionary studies in squamate reptiles.

Smooth snake population decline and its link with prey availability

The relationship between the numbers of smooth snakes, Coronella austriaca, and common lizards, Zootoca vivipara, was investigated in a 6.5 ha area of lowland heath within Wareham Forest in southern England. With the exception of 2002 the numbers of lizards, small mammals and individual smooth snakes captured, or observed, were recorded during each of 21 annual surveys between May and October 1997-2018. Smooth snake diet was investigated annually between 2004 and 2015 by analysing faecal samples and showed that lizards, particularly the common lizard, and pigmy shrews, Sorex minutus, were important prey species. There was no significant correlation between the occurrence of any small mammal species and either snake numbers or their presence in smooth snake diet. Over the study period there was an overall decline in the number of smooth snakes captured whilst there was an overall increase in the number of common lizard sightings. The frequency of common lizards found in the diet of smooth snakes was positively correlated with their abundance within the study area. There was a significant correlation between the decline of smooth snake numbers and the subsequent increase in the number of common lizard sightings suggesting that lizard abundance may be controlled by snake numbers. Conversely, we found no evidence indicating that smooth snake numbers were dependent on lizard numbers suggesting that factors other than prey availability e.g. habitat change due to cattle grazing, blocking ground water drainage ditches, or climatic variables, were impacting on snake numbers, particularly between 2012 and 2018.

Factors influencing the level of infestation of Ixodes ricinus (Acari: Ixodidae) on Lacerta agilis and Zootoca vivipara (Squamata: Lacertidae)

The purpose of this study was to analyse selected factors determining the level of infestation of Ixodes ricinus ticks on Lacerta agilis and Zootoca vivipara lizards found in Central Europe. Both environmental factors (habitats within protected areas and areas transformed as a result of human activity) as well as morphological factors (age, sex and size of lizards, location of ticks on the lizard’s body) were assessed. We found that the age and size of a lizard played a significant role in the level of infestation, but this depended on the species and habitat. Females of both species differed significantly in their level of tick infestation; females of L. agilis had lower infection than Z. vivipara. In contrast, there was no difference in levels of infection between juveniles and males of the different species. We also found that the impact of body size changed in the different habitats: the number of ticks increased with body size in natural areas only. In addition, more frequently ticks were found in the front groin area (336 individuals) and forelimbs (202), less often on the neck (12) and never in the hind groin area. These differences might be because it is easier to infest a larger individual than a smaller one, and areas of the front of the lizard might be more accessible whilst foraging. This study provides additional information about tick infestation that may be relevant to the conservation of the species of lizards.