Patterns of multiple paternity within and between annual reproduction cycles of the fire salamander (Salamandra salamandra) under natural conditions

We have investigated patterns of paternity in a population of the fire salamander Salamandra salamandra in Germany under fully natural conditions. Pregnant females were caught after hibernation in their natural habitat and their offspring were genotyped with different sets of microsatellite loci to assess paternity. Each female was marked with a transponder and released at the same place where it had been caught. We were able to recapture several marked females in the following years and to analyse the offspring arrays of six females for different reproductive years between 2000 and 2001 for possible long-term sperm storage and repeated sperm usage. The reconstruction of paternal genotypes for 21 female offspring arrays with the GERUD 1.0 program showed that multiple paternity is frequent under natural conditions with more than half of the females showing two or three fathers for their offspring cohorts. Despite the fact that S. salamandra is capable of long-term sperm storage under captive conditions, under natural conditions we did not find evidence for long-term sperm storage and repeated sperm usage for the six analysed female offspring arrays from consecutive years. This might be an indication for possible cryptic female choice owing to differences of sperm quality between stored and freshly uptaken sperm or degradation of sperm after fertilization. Furthermore, we found that males in nature do not contribute equally to a female's clutch when it is sired from multiple fathers. Currently, it is not clear whether such a paternity pattern reflects a simple 'topping off' mechanism of sperm in the spermathecae of the female as described for the newt species Taricha granulosa or whether this is the result of intensive sperm competition.