MICROSATELLITE ANALYSIS OF MATERNITY AND THE MATING SYSTEM IN THE GULF PIPEFISH SYNGNATHUS-SCOVELLI, A SPECIES WITH MALE PREGNANCY AND SEX-ROLE REVERSAL

Highly variable microsatellite loci were employed td study the mating system of the sexually dimorphic Gulf pipefish Syngnathus scovelli. In this species, like others in the family Syngnathidae, 'pregnant' male s provide all parental care. Gulf pipefish were collected from one loc ale in the northern Gulf of Mexico, and internally carried broods of 4 0 pregnant males were analysed genetically. By comparing multilocus mi crosatellite fingerprints for the inferred mothers against expected ge notypic distributions from the population sample, it was determined th at: (i) only one male had received eggs from more than a single female ; and (ii) on two separate occasions, two different males had received eggs from the same female. Given the high power to detect multiple ma tings by males, the first finding indicates that only rarely are indiv idual males impregnated by multiple females during the course of a pre gnancy. Conversely, given the lower power to detect multiple matings b y females due to sampling constraints, the second finding suggests a h igh frequency of multiple successful matings by females. Thus, this po pulation of Gulf pipefish displays a polyandrous genetic mating system . The relevance of these genetic findings is discussed with regard to the evolution of secondary sex traits in this species, and in other sy ngnathids.