Factors shaping the gut microbiome of five species of lizards from different habitats.

Background: Host-gut microbiota interactions are complex and can have a profound impact on the ecology and evolution of both counterparts. Several host traits such as systematics, diet and social behavior, and external factors such as prey availability and local environment are known to influence the composition and diversity of the gut microbiota. Methods: In this study, we investigate the influence of systematics, sex, host size, and locality/habitat on gut microbiota diversity in five lizard species from two different sites in Portugal: Podarcis bocagei and Podarcis lusitanicus, living in syntopy in a rural area in northern Portugal (Moledo); the invasive Podarcis siculus and the native Podarcis virescens, living in sympatry in an urbanized environment (Lisbon); and the invasive Teira dugesii also living in an urban area (Lisbon). We also infer the potential microbial transmission occurring between species living in sympatry and syntopy. To achieve these goals, we use a metabarcoding approach to characterize the bacterial communities from the cloaca of lizards, sequencing the V4 region of the 16S rRNA. Results: Habitat/locality was an important factor explaining differences in gut bacterial composition and structure, with species from urbanized environments having higher bacterial diversity. Host systematics (i.e., species) influenced gut bacterial community structure only in lizards from the urbanized environment. We also detected a significant positive correlation between lizard size and gut bacterial alpha-diversity in the invasive species P. siculus, which could be due to its higher exploratory behavior. Moreover, estimates of bacterial transmission indicate that P. siculus may have acquired a high proportion of local microbiota after its introduction. These findings confirm that a diverse array of host and environmental factors can influence lizards' gut microbiota.

What Influences the Prevalence and Intensity of Haemoparasites and Ectoparasites in an Insular Lizard?

Island biogeography theories predict that characteristics such as island size, age, and isolation interplay in host-parasite dynamics. In this study, we analyzed haemogregarines of the Aegean wall lizard, Podarcis erhardii, to investigate how island characteristics relate to parasite prevalence and intensity. A previous assessment of 19 Greek island populations suggested that isolation time and host population density were key predictors of haemogregarines. Here, by combining microscopy and genetic techniques, we extend this previous study to four additional islands: Syros, Folegandros, Santorini and Nea Kameni. We also recorded the prevalence of ticks and mites, definitive hosts for these parasites. The genetically identified haemogregarines are part of a clade with parasites from other lizard species, including some considered as Karyolysus, but others assigned to Hepatozoon. The prevalence of these parasites differed significantly between islands, while their intensity did not. The presence of ticks was associated with endoparasite prevalence, and males were more frequently infected by haemogregarines than females. Combining our data with that of the previous study, we found no significant impact of the island age and area on parasite prevalence. We also confirmed the presence of the unrelated parasite genus Schellackia through microscopy and DNA sequencing, which is the first record of this genus in this host species. Our results further highlight the complexity of host-parasite systems.

Blood parasite diversity (Apicomplexa: Haemogregarinidae) within the western populations of the European pond turtle Emys orbicularis.

Molecular tools have revolutionized assessments of blood parasites in freshwater turtles. In the Iberian Peninsula and North Africa, two native species of terrapins occur, Emys orbicularis (Linnaeus) and Mauremys leprosa (Schweigger). Both have been identified as hosts for the blood parasite Haemogregarina stepanowi Danilewsky, 1885, which has also been found in related species. However, recent assessments of M. leprosa have identified several distinct genetic lineages of these parasites in this host, while only three haemogregarine lineages were identified in E. orbicularis in Tunisia. Here, we screened 215 individuals of E. orbicularis from the Iberian Peninsula, Menorca Island and Morocco for haemogregarine parasites using partial 18S rRNA gene sequences to estimate relationships. Three unrelated lineages of parasites were detected, one presumed H. stepanowi and two lineages previously known from M. leprosa. A considerable undescribed diversity of parasites exists within these vertebrate host species, while mixed infection and host-sharing is also widespread. Considering that E. orbicularis is near threatened in this region, it is of great importance to identify the parasites infecting it, and to further assess the potential deleterious impact of these diverse parasites on their hosts.

Invasive lizard has fewer parasites than native congener.

Invasive species can carry parasites to introduced locations, which may be key to understand the success or failure of species establishment and the invasive potential of introduced species. We compared the prevalence and infection levels of haemogregarine blood parasites between two sympatric congeneric species in Lisbon, Portugal: the invasive Italian wall lizard (Podarcis siculus) and the native green Iberian wall lizard (Podarcis virescens). The two species had significant differences in their infection levels: while P. virescens had high prevalence of infection (69.0%), only one individual of P. siculus was infected (3.7%), and while P. virescens exhibited an average intensity of 1.36%, the infected P. siculus individual had an infection rate of only 0.04%. Genetic analyses of 18S rRNA identified two different haemogregarine haplotypes in P. virescens. Due to the low levels of infection, we were not able to amplify parasite DNA from the infected P. siculus individual, although it was morphologically similar to those found in P. virescens. Since other studies also reported low levels of parasites in P. siculus, we hypothesize that this general lack of parasites could be one of the factors contributing to its competitive advantage over native lizard species and introduction success.

Learning from others: an invasive lizard uses social information from both conspecifics and heterospecifics.

Species that are able to solve novel problems through social learning from either a conspecific or a heterospecific may gain a significant advantage in new environments. We tested the ability of a highly successful invasive species, the Italian wall lizard Podarcis sicula, to solve a novel foraging task when social information was available from both a conspecific and an unfamiliar heterospecific (Podarcis bocagei). We found that Italian wall lizards that had access to social information made fewer errors, regardless of whether the demonstrator was a conspecific or a heterospecific, compared to Italian wall lizards that individually learnt the same task. We suggest that social learning could be a previously underappreciated, advantageous mechanism facilitating invasions.

Intraspecific Colour Variation among Lizards in Distinct Island Environments Enhances Local Camouflage.

Within-species colour variation is widespread among animals. Understanding how this arises can elucidate evolutionary mechanisms, such as those underlying reproductive isolation and speciation. Here, we investigated whether five island populations of Aegean wall lizards (Podarcis erhardii) have more effective camouflage against their own (local) island substrates than against other (non-local) island substrates to avian predators, and whether this was linked to island differences in substrate appearance. We also investigated whether degree of local substrate matching varied among island populations and between sexes. In most populations, both sexes were better matched against local backgrounds than against non-local backgrounds, particularly in terms of luminance (perceived lightness), which usually occurred when local and non-local backgrounds were different in appearance. This was found even between island populations that historically had a land connection and in populations that have been isolated relatively recently, suggesting that isolation in these distinct island environments has been sufficient to cause enhanced local background matching, sometimes on a rapid evolutionary time-scale. However, heightened local matching was poorer in populations inhabiting more variable and unstable environments with a prolonged history of volcanic activity. Overall, these results show that lizard coloration is tuned to provide camouflage in local environments, either due to genetic adaptation or changes during development. Yet, the occurrence and extent of selection for local matching may depend on specific conditions associated with local ecology and biogeographic history. These results emphasize how anti-predator adaptations to different environments can drive divergence within a species, which may contribute to reproductive isolation among populations and lead to ecological speciation.

First report of Hepatozoon (Apicomplexa: Adeleorina) in caecilians, with description of a new species.

Hepatozoon spp. are identified for the first time in the amphibian order Gymnophiona, or caecilians, from the Seychelles island of Silhouette. Estimate of relationships derived from partial 18S rRNA gene sequences indicate these are not related to Hepatozoon spp. from frogs or to other Hepatozoon spp. from reptiles in the Seychelles. Assessment of mature gamonts from blood smears indicate that these can be recognized as a new species, Hepatozoon seychellensis n. sp.