Specific Mate Recognition Systems (SMRS) consist of a set of morphological, behavioural and physiological traits which allow mate recognition. The Limnocytherinae, a lineage of non-marine podocopid Ostracoda, have a relatively wide diversity of copulatory modules, a concept largely congruent with the morphological part of the SMRS. The present paper describes the various copulatory modules in some detail and discusses potential mechanisms responsible for the divergence of these modules. Although none of the processes was thus far demonstrated directly, resulting patterns provide indirect evidence that four different mechanisms contribute. Stochastic processes (chance) as well as developmental and other phylogenetic constraints are involved in the initial selection (choice) of modified structures. Subsequent (positive) directional sexual selection on traits of the recognition systems causes radiative speciation within lineages. At all times, natural selection acts on the development of these structures, either stabilising or negative directional. A number of potential tests for these hypotheses are suggested.