Paternity Outcomes in the Freshwater Gastropod, Chilina dombeiana in the Biobío River, Chile

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.

High levels of multiple paternity in a spermcast mating freshwater mussel

“…Not only do our results offer additional evidence of multiple paternity in unionid mussels, our findings illustrate the potential of genetic methods for estimating demographic parameters, including population size. River ecosystems are highly vulnerable to fragmentation, which can prevent completion of bidirectional migratory life cycles like those exhibited by freshwater mussels (Bórquez & Brante, ). Rivers worldwide are subject to a high level of human disturbance and have been experiencing an exceptionally rapid loss of biodiversity (Vörösmarty et al., ).…”

Exceptional preservation in Quaternary Atacama Desert Tufas: Evidence for increased groundwater and surface water in the Calama Basin, Atacama, Chile

“…The presence of ostracod and diatom fossils adhering to Santa Juana stromatolite filaments indicates that the stromatolites grew subaqueously, hosting a thriving biota, implying oxic conditions within the photic zone. The presence of gastropod shells suggest that the stromatolites were grazed by snails, as occurs in modern South American rivers (Bórquez & Brante, 2017;Ovando & Gregoric, 2012). The Loa, San Salvador and other nearby rivers have water conditions due to their delicate form (Narbonne et al, 2000).…”

Multiple mating by both sexes in an invasive insect species, Aethina tumida (Coleoptera: Nitidulidae)

“…Based on this assumption, the minimum number of males was estimated as half the number of nonmaternal alleles at each locus. However, since this method only provides the minimum number of fathers, which is most likely an underestimation, the number of fathers was also estimated by using software COLONY v 2.0.6.6 (Jones & Wang, 2010) that estimates numbers of putative sires based on a maximum-likelihood approach commonly used in paternity studies (Awad et al, 2015;Bórquez & Brante, 2017). The following settings were chosen for the COLONY runs: mating system with both male and female polygamy; inbreeding without clone; diploid dioecious species; medium length run with fulllikelihood analysis method; no sib ship prior.…”