Introduction
A myriad of microorganisms can be found living in the gastrointestinal
tract of all animals. These microorganisms have a significant impact on
host biology and can influence a variety of processes that affect host
fitness (Cryan & Dinan, 2012; Thaiss et al. 2016). While certain
variations in the composition of gut microbial communities can cause
disease (Martin et al. 2014; Boursier et al. 2016), gut microbiome may
also increase resistance to pathogens, besides being important for
xenobiotics metabolism, nutrient uptake and energy acquisition [e.g.
Vavre & Kremer, 2014; Rowland et al. 2018). Moreover, gut microbiota
may also contribute towards host adaptation to environment changes by
enabling a response to new challenges, such as exploitation of novel
food sources (Delsuc et al. 2014; Hammer & Bowers, 2015). Ultimately,
gut microbiome can have a major impact on host development, behaviour
and fitness, with cascading effects to the dynamics of ecosystems
(Thaiss et al. 2016). In turn, it can also be modulated by several host
traits, such as host evolutionary history, sex and size, as well as the
external environment, such as habitat or prey availability (e.g., Muegge
et al. 2011; Xavier et al. 2019). In addition, social interactions
between hosts can also influence the gut microbiome in many animal
species, although these mechanisms remain less studied (see review by
Archie & Tung, 2015).
Gut microbiome dynamics has been studied in many mammals (e.g., Thaiss
et al. 2016), birds (e.g., Hird et al. 2015), fishes (e.g., Xavier et
al. 2020) and amphibians (e.g., Bletz et al. 2016). Comparatively fewer
studies have been performed in reptiles, and only a handful of these
addressed lizards. Nevertheless,
studies showed that maternal transmission of gut microbiota to offspring
can occur in squamate reptiles (Kohl et al. 2017). Additionally,
microbiota can be acquired by reptiles through horizontal transmission
from the environment or through interaction with other organisms (e.g.
predatory encounters, Colston, 2017). Host systematics and ecology were
also seen to be important drivers of gut microbiota diversity in
reptiles. For example, feeding habits influence the gut microbiota of
the Chinese crocodile lizard, Shinisaurus crocodilurus Ahl 1930,
with potential effects on host health due to the influence of diet on
the abundances of pathogenic or opportunistic gut bacteria (Jiang at al.
2017). Diet and habitat of the Australian water dragon,Intellagama lesueurii (Gray, 1831), also have an effect on its
gut microbiome, with lizards living in urban areas presenting higher
bacterial diversity than populations living in natural habitats
(Littleford-Colquhoun et al. 2019). Moreover, host systematics and
habitat also influence the gut microbiota of venomous snakes (Smith et
al. 2021).
Here, we analyze and compare the diversity, composition and structure of
gut bacterial communities of five related lacertid species captured in
Portugal. Individuals of Podarcis bocagei (Lopez-Seoane, 1885)
and Podarcis lusitanicus Geniez, Sá-Sousa, Guillaume, Cluchier
and Crochet, 2014, were sampled in Moledo (North of Portugal) where they
live in syntopy. Invasive Podarcis siculus (Rafinesque-Schmaltz,
1810) and native Podarcis virescens Geniez, Sá-Sousa, Guillaume,
Cluchier and Crochet, 2014, were sampled from Parque das Nações (Lisbon)
where they live in sympatry. Finally, a population of the invasiveTeira dugesii (Milne-Edwards, 1829) was sampled in the Alcantara
Docks in Lisbon. All five species
exhibit sexual dimorphism, with males usually being larger than females,
and they are mostly insectivorous (Geniez et al. 2014; Carretero et al.
2015), although P. siculus and Teira dugesii may also
occasionally consume some fruits or flowers (Mačát et al. 2015).Podarcis species are considered model organisms to study
ecotoxicology, immune/histochemical reactions, among other processes
[e.g. Bicho et al. 2013; Luís et al. 2019);
however,
microbiome studies are still largely lacking, with only three studies
available to data. Two studies investigated two species endemic to the
Balearic Islands (Spain), Podarcis lilfordi (Günther, 1874) andPodarcis pityusensis (Bosca, 1883), with results indicating that
islet, time since separation from mainland and seasonality are
significant factors contributing to their gut microbiome (Baldo et al.
2018, Alemany et al. 2022). Another recent study compared the gut
microbiota of two Italian populations of P. siculus (mainland vs
island) demonstrating that there were considerable differences between
the two (Buglione et al., 2022).
Our main objective was to determine whether locality, which also
corresponded to two different habitats (rural vs urbanized) and host
factors such as species, size and sex modulate the gut bacterial
diversity of these five lizards. To achieve this, we used cloacal swabs
to obtain a proxy for gut bacterial communities which were characterized
by sequencing the V4 region of the 16S rRNA gene. Swabs were preferred
to fecal samples as these more accurately reflect microbial communities
residing in lower gut and cloacal tissues (Bunker et al. 2021).