ABSTRACT
WHAT ARE ALTERNATIVE REPRODUCTIVE TACTICS?
In some species, individuals of the same sex adopt alternative tactics to compete for mates. Instead of basing their intra-sexual competition in the investment of resources towards the attraction and monopolisation of sex partners (e.g. expression of visual, chemical or acoustic courtship signals and/or the defense of breeding territories), individuals using the alternative tactic exploit the investment made by conventional individuals (e.g., by sneaking into the breeding territories during spawning episodes). Therefore, the terms bourgeois and parasitic have been proposed to describe these two tactics (Taborsky, 1997) and the traits selected in the two male types are usually divergent. In bourgeois males,
traits related with mate attraction and monopolisation will be selected, while in parasitic males those traits that increase the probability of stealing fertilisations from bourgeois males will prevail. This disruptive selection, acting on a constellation of phenotypic traits, may result in the evolution of polyphenisms within one sex, usually the males, where the expression of male reproductive behaviour and male secondary sex characters in parasitic males becomes dissociated from the differentiation of a functional male gonad. In summary, alternative reproductive tactics (ART) are discontinuous behavioural and morphological traits selected to maximise fitness in two or more mutually exclusive ways in the context of reproductive competition. Based on the descriptive patterns of observed behaviour, alternative reproductive phenotypes can be categorised as fixed or plastic (Moore, 1991; Brockmann, 2001). In fixed alternative phenotypes, the individuals adopt one of the tactics for their entire lifetime. In plastic (or flexible) alternative phenotypes, the individuals may change tactics during their lifetime. Within plastic ART, again, two subcategories can be further distinguished: irreversible sequential patterns, when individuals switch from one tactic to another at a particular moment in their lifetime (developmental switches); and reversible patterns, when individuals can change back and forth between patterns (Moore, 1991; Moore et al., 1998; Brockmann, 2001; Fig. 4.3.1).
