Morph-specific seasonal variation of aggressive behaviour in a polymorphic lizard species

Abstract

The persistence of colour polymorphism (CP) within a given population is generally associated with the coexistence of alternative reproductive strategies, each one involving specific trade-offs among behavioural, morphological, physiological, and other life histories. Common wall lizard (Podarcis muralis), is a medium-sized diurnal lizard, showing CP in three main colours (yellow, white, and red) on throat and belly, and a morph-specific pattern for both immunocompetence and seasonal variation of T levels. Yellow males show low stamina with high plasma T levels at the beginning of the season, while white males show high stamina with a higher plasma T levels at the end of the season. We hypothesised the presence of two strategies: a risky one, characterised by high aggressiveness played by yellow-morph, and a conservative one by white morph with low aggressiveness. Thus, we tested the aggressive response to conspecifics of yellow and white morphs using a mirror inserted into their cage, mimicking an intrusion of a stranger in their territories, throughout the breeding season (from April to July, 117 trials). We considered three types of aggressive response, with different levels of aggressiveness: (i) bite against the image reflected in the mirror, (ii) seconds spent by the individuals into the half mirrored cage, and (iii) number of times the lizard entered the half mirrored cage. We also considered the number of tongue flicking as explorative behaviour variable. All lizards were tested after a period of acclimatisation to the captivity conditions. Results demonstrate that yellow males showed a higher aggressive response in the early season and a decrease aggressive response towards the end, whereas white males showed an opposite pattern.

Colour variation of the Maltese wall lizards (Podarcis filfolensis) at population and individual levels in the Linosa island

“…Upper panels report differences between sexes in each body; lower panels report the effect of body size (SVL) on colouration in males and females in each of the three body regions. HSM (white circles), HDI 50 (thick lines), and HDI 95 (thin lines) estimates are shown; females are in black, males in grey Coladonato et al 2020), and both sexes are under significant risk from visually oriented predators, namely birds, including raptors and corvids (Martin and Lopez 1996;Castilla et al 1999;Biaggini et al 2010). Therefore, it is likely that both conspicuous sexual signals and antipredator colouration (i.e., camouflage) are present in P. filfolensis, as it occurs on the other congeneric species.…”

Close encounters of the three morphs: Does color affect aggression in a polymorphic lizard?

“…Some other displays were observed during the experiments (e.g., tongue‐flicking, hand‐shaking, tail‐shaking, etc. ), but we only considered those ones that could be interpreted as aggressive interactions toward the opponent and not those related to stress or explorative behavior (Coladonato et al, 2020; Sacchi et al, unpublished data).…”

“…Previous studies demonstrated that this species expresses a pigment‐based ventral color polymorphism in both sexes with three discrete color morphs (white, yellow, and red; Sacchi et al, 2013; Sacchi et al, 2007). Morphs are genetically determined (Andrade et al, 2019) and correlations between morphs and aggressiveness remain controversial (Abalos et al, 2016; Coladonato et al, 2020; Sacchi et al, 2009). In a previous study using a resident‐intruder design, Sacchi et al (2009) showed that simple rules, such as residency and body size differences, determine the outcome of agonistic encounters but the authors did not find any effect of color on male aggression or fighting success.…”

“…The hormone profile did not differ between red and white males (Sacchi et al, 2017). Accordingly to seasonal variation in hormone profile, Coladonato et al (2020) were able to detect morph‐specific differences in the seasonal pattern of variation in the aggressive behavior of yellow males compared to males of the white morphs, but not among white, yellow, and red males. Overall, no clear picture emerges from these studies, so a study able to prevent any confounding effect given by staged contest is needed to fully understand the role of visual badges in releasing aggressive behaviors and the strategies adopted by each morph.…”

No genomic repercussions of assortative pairing in a colour polymorphic lizard

“…Furthermore, several studies have highlighted differences between morphs of P . muralis on their behaviour, morphology, physiology and reproductive strategy (e.g., Calsbeek et al, 2010; Coladonato et al, 2020; Galeotti et al, 2013; Sacchi et al, 2018; Sreelatha et al, 2021), although other studies did not find empirical support for these differences, arguing against the existence of alternative strategies (e.g., Abalos et al, 2020, 2022; Sacchi et al, 2015).…”