Androgen responses to reproductive competition of males pursuing either fixed or plastic alternative reproductive tactics

Abstract

Alternative reproductive tactics (ARTs), which can be plastic or fixed for life, may be characterized by distinct hormonal profiles. The relative plasticity hypothesis predicts flexible androgen regulation for adult males pursuing plastic tactics, but a less flexible regulation for males using a fixed tactic throughout life. Furthermore, androgen profiles may respond to changes in the social environment, as predicted by the social reciprocity models of hormone/behaviour interactions. The cichlid fish Lamprologus callipterus provides a rare opportunity to study the roles of androgens for male ARTs within a single species, because fixed and plastic ARTs coexist. We experimentally exposed males to competitors pursuing either the same or different tactics to test predictions of the relative plasticity and the social reciprocity models. Androgen profiles of different male types partly comply with predictions derived from the relative plasticity hypothesis: males of the plastic bourgeois/sneaker male trajectory showed different 11-ketotestosterone (11-KT) levels when pursuing either bourgeois or parasitic sneaker male behaviours. Surprisingly, males pursuing the fixed dwarf male tactic showed the highest free and conjugated 11-KT and testosterone (T) levels. Our experimental social challenges significantly affected the free 11-KT levels of bourgeois males, but the androgen responses did not differ between challenges involving different types of competitors. Furthermore, the free T-responses of the bourgeois males correlated with their aggressive behaviour exhibited against competitors. Our results provide new insights into the endocrine responsiveness of fixed and plastic ARTs, confirming and refuting some predictions of both the relative plasticity and the social reciprocity models.

Genomic basis of Y‐linked dwarfism in cichlids pursuing alternative reproductive tactics

“…It is possible that a mutation in the GHRHR candidate body size gene gave rise to dwarf males that had higher fitness due to their efficient parasitic reproductive tactic (Taborsky et al, 2018; Wirtz‐Ocana et al, 2014). This high fitness allowed the new dwarfism mutation to establish and be maintained by negative frequency‐dependent selection in the population (Clark, 1987; Gadgil, 1972), as the fitness of each type of males is dependent on their relative frequency in the population (Taborsky & Brockmann, 2010; Taborsky, 2008; von Kuerthy et al, 2016). Such Y haplotype diversity has also been observed in guppies ( Poecilia reticulata ) that experience negative frequency‐dependent selection on Y‐linked colour patterns, as well as in the closely related species Poecilia parae in which there are five behaviourally and morphologically distinct reproductive male morphs that each have a distinct Y‐haplotype (Almeida et al, 2020; Sandkam et al, 2021).…”

Exploring the Relationship Between Physiological Performance and Reproductive Investment in Wild Fish Using Heart Rate Biologgers

“…blood sample before and after the event) to obtain snapshots of the animal's physiological condition and to observe net changes (e.g. Iwama et al 1989;Patterson et al 2004;Crossin et al 2008;Kuerthy et al 2016). However, with recent technological development, the ability to monitor continuous, real-time data is improving and opening the opportunity to validate the hypothesis that reproduction behaviour and fitness are related to an individual's physiological performance (reviewed in Cooke et al 2004;).…”

“…Slomanand Armstrong 2002;Perry et al 2004). However, most research has focused on relating reproductive behaviour with morphological variables, such as size(Quinn and Foote 1994) and secondary sexual characteristics(Shine 1979; Clutton-Brock 2009), or long-acting sex hormones(Brantley et al 1993;Oliveira et al 2001;Kuerthy et al 2016). Therefore, research validating the role of real-time variation in physiological performance on dominance behaviour during reproduction is limited.…”