Proposed benefits of multiple paternity include increased reproductive output, elevated fitness of progeny, and maintenance of population genetic diversity. However, another consideration is whether multiple paternity is simply an unavoidable byproduct of sexual conflict, with males seeking to maximize mating encounters while females seek to minimize the stress of copulation. Here we examined the polyandrous mating system in sharks, with a focus on the reproductive genetics of the shortspine spurdog Squalus mitsukurii. Members of the genus Squalus are long-lived, slow-growing, and employ among the longest gestation periods of any vertebrate. To evaluate multiple paternity and genetic diversity in S. mitsukurii, we genotyped 27 litters plus 96 individuals with 8 microsatellite loci. Further, 670 bp of the mtDNA control region were sequenced in 112 individuals to examine population structure. S. mitsukurii in Hawaii showed low genetic diversity relative to other sharks (π = 0.0010 ± 0.0008) and no significant population structure in the Hawaiian Archipelago. Direct allele counts and Bayesian approximations returned concordant estimates of 11% multiple paternity, the lowest observed in sharks to date. Considering the protracted reproductive interval of S. mitsukurii, sexual conflict that results from differential male and female reproductive strategies may favor the development of female mating avoidance behavior to minimize trauma. In S. mitsukurii this behavior includes segregation of sexes and an asynchronous reproductive cycle.KEY WORDS: Elasmobranch · Polyandry · Control region · Microsatellite DNA · Population structure · Sexual conflict · Sexual segregation · Reproductive strategy
Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 403: [255][256][257][258][259][260][261][262][263][264][265][266][267] 2010 females with conventional sex roles (reviewed by Zeh & Zeh 2003). Polyandry (females mating with more than one male) and multiple paternity (a single brood of offspring sired by multiple males) are now recognized as common strategies in widely divergent taxa including amphibians, mammals, reptiles, insects, crustaceans, and fishes (Evans & Magurran 2000, Toonen 2004, Adams et al. 2005, Bretman & Tregenza 2005, Daly-Engel et al. 2006, Dean et al. 2006, Jensen et al. 2006. It is still unclear, however, what roles sexual conflict and intersexual selection might play in polyandrous mating systems.For males, the advantages to having multiple breeding partners are clear: the more females a male inseminates, the more offspring he fathers and the greater his reproductive fitness. The benefits of polyandry to females are less obvious. Potential direct benefits to the female include nuptial gifts or parental care on the part of the male. No direct benefits have been shown in shark mating systems, though there is potential for indirect or genetic benefits through polyandrous mating. If there is little or no opportunity to evaluate males prior to copulation, a f...