Genetic markers substantiate long-term storage and utilization of sperm byfemale painted turtles

Most studies of genetic parentage in natural populations have been limited to a single breeding season or reproductive episode and, thus, provide only a snapshot of individuals' mating behaviours. Female turtles can store via ble sperm in their reproductive tracts for as long as several years, but th e extent to which this capacity is utilized in nature has remained unknown. Here, we employ microsatellite markers to assess genetic paternity in succ essive clutches or individually marked, free-ranging female painted turtles (Chrysemys picta) over a four year period. The genetic data from 113 clutc hes from this natural population demonstrate that most females (80.5%) rema ted each year and that each female generally used a single male's sperm to fertilize all clutches laid within a year. However, sperm usage among femal es varied considerably, and some females apparently used sperm that had bee n stored for up to three years to fertilize some or all eggs laid in consec utive nesting seasons. Thus, remating by females is not necessary for conti nued offspring production from a given sire, Furthermore, 13.2% of all clut ches examined showed evidence of multiple paternity, and the genetic patern ity patterns across years suggest a 'last in, first out' operation of the f emales' sperm storage tubules.