Abstract
Studying the mating system of obligate aquatic organisms that inhabit river ecosystems is important for understanding its evolution as well as the role of biological and environmental factors in modulating population dynamics and species distributional patterns. Here, we studied the reproductive strategy of the Chilean endemic freshwater snail, Chilina dombeiana, in the Biobío River, one of the largest rivers in Chile. This species has a low potential for dispersal given the absence of a free-swimming larval stage (benthic larval development) and given that adults have a low capacity for mobility. We hypothesized that: 1. Females would mate with different males (polyandry) resulting in intrabrood multiple paternity, 2. Individuals from closer sites would be more related than individuals from distant sites, and 3. Male parental contributions would be unevenly distributed within broods. Individuals from three different sites were sampled along the river: upper, mid, and river mouth. In the laboratory, hatching juveniles from a total of 15 broods were collected for paternity analyses. We used microsatellite markers and the programs GERUD and COLONY to determine whether multiple paternity exists and to estimate the contribution of different males to the brood. We found that multiple paternity was very common at all of the sites analyzed with as many as 8 males fertilizing a single female and a mean of 4.2 fathers per brood estimated by COLONY. Sire contribution was skewed to particular males in several broods. In addition, overall relatedness among broods for the three sites ranged from 0.17 to 0.45 with evidence of many half-siblings. Relatedness differed among the three sites. Particularly in upstream sites or in anthropogenically disturbed populations, the high levels of multiple paternity observed in C. dombeiana may be an efficient strategy to avoid inbreeding and prevent the loss of genetic diversity within populations.
Highlights
Polyandry, the act of a female mating with multiple males, is one of the most common mating systems observed in nature and has been reported in many taxonomic groups [1,2,3,4,5,6,7,8].PLOS ONE | DOI:10.1371/journal.pone.0169574 January 9, 2017Multiple Paternity in Chilina dombeianaOften, polyandry results in multiple paternity with females laying eggs fertilized by different males, and male contribution to the brood occurs in different proportions [9]
No conservation or management policies are considered for C. dombeiana and the study was not conducted in protected areas, no specific permission was required for sampling individuals
Multiple paternity has been frequently observed in marine gastropod mollusks, little is known about paternity in freshwater snails
Summary
Polyandry results in multiple paternity with females laying eggs fertilized by different males, and male contribution to the brood occurs in different proportions [9]. There are individual costs and benefits to polyandry; for example, costs include increased exposure to sexually transmitted disease [10], increased risk of predation [11,12,13], and potential effects on foraging behavior [14]. Due to the greater supply and increased quality of sperm [15,16] resulting from polyandry, potential benefits could include increased fertilization success [14] and prevention of the deleterious effects of inbreeding depression [17,15]. Higher genetic variability among siblings within a brood has been observed as a result of polyandry; offspring could have a higher evolutionary potential to respond to environmental changes [18,15,19]
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