Male scent-marks predict fitness via socio-spatial dominance, but not female choice, in a lacertid lizard

Javier Abalos , Alicia Bartolomé, Guillem Pérez i de Lanuza, Fabien Aubret, Tobias Uller, Pau Carazo , Enrique Font, Roberto García-Roa

Chemical communication via scent-marks is widely recognised as a key mediator of sexual selection in lizards, yet their role remains contentious because we mostly ignore how scent-mark composition ultimately impacts male fitness in nature. Male scent-marks are often proposed to function as condition-dependent honest sexual signals mediating female choice, but an arising alternative hypothesis is that they primarily function in male–male competition. We provide a comprehensive test of these competing hypotheses. We studied common wall lizards (Podarcis muralis) in outdoor enclosures and combined chemical analyses of scent-marks with detailed behavioural and spatial data, genetic parentage assignment, and path analysis to quantify how scent composition relates to mating behaviour, contest outcomes, sperm competition, and male reproductive success. We found no evidence that females assess mates based on candidate compounds proposed as signals of male quality, or that these predict hatchling mass (i.e. no evidence of potential indirect benefits of female choice). Instead, female settlement and fertilisation patterns were driven by resource distribution and spatial proximity. Furthermore, several compounds correlated with dominance and male–male competition emerged as the primary driver of reproductive success, strongly suggesting that scent-marks mediate territorial dynamics, rather than female choice.