Frequency of Multiple Paternity in Tope (Galeorhinus galeus) from California and Australia

Multiple paternity (MP) has been widely documented in elasmobranch fishes (sharks, rays, and skates); however, the frequency of multiple paternity (FMP; the percentage of sampled litters having multiple sires) varies greatly between and within species. Understanding the reasons for this inter- and intraspecific variation in FMP may be key to understanding why females mate with multiple males. For the Tope (Galeorhinus galeus), one previous study detected multiple paternity in two out of five litters sampled from New Zealand (FMP = 40.0%), an unexpectedly low FMP given this species’ reproductive biology and ecology. To further test the hypothesis of low FMP in G. galeus, we expanded on previous work by genotyping an additional ten litters sampled from central South Australia, Australia (mean litter size = 32.6 ± 7.8 pups) as well as ten litters sampled from southern California, USA (mean litter size = 30.9 ± 8.5 pups). Multiple paternity was detected in four of the ten litters sampled from Australia (FMP = 40.0%) and two of the ten litters sampled from California (FMP = 20.0%). Our results support the hypothesis that MP occurs at a relatively low frequency in G. galeus, as compared to other elasmobranch species.